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chromium / external / dynamorio / 3d4cffbe9e218b1d5e75a80a65b66bee7d9a642d / . / core / synch.c
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/* **********************************************************
* Copyright (c) 2012-2014 Google, Inc. All rights reserved.
* Copyright (c) 2008-2010 VMware, Inc. All rights reserved.
* **********************************************************/
/*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of VMware, Inc. nor the names of its contributors may be
* used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL VMWARE, INC. OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*/
/*
* thread.c - thread synchronization
*/
#include "globals.h"
#include "synch.h"
#include "instrument.h" /* is_in_client_lib() */
#include "hotpatch.h" /* hotp_only_in_tramp() */
#include "fragment.h" /* get_at_syscall() */
#include "fcache.h" /* in_fcache() */
#include "translate.h"
#include <string.h> /* for memcpy */
extern vm_area_vector_t *fcache_unit_areas; /* from fcache.c */
static void
synch_thread_yield(void);
/* Thread-local data
*/
typedef struct _thread_synch_data_t {
/* the following three fields are used to synchronize for detach, suspend
* thread, terminate thread, terminate process */
/* synch_lock and pending_synch_count act as a semaphore */
/* for check_wait_at_safe_spot() must use a spin_mutex_t */
spin_mutex_t *synch_lock;
/* we allow pending_synch_count to be read without holding the synch_lock
* so all updates should be ATOMIC as well as holding the lock */
int pending_synch_count;
/* to guarantee that the thread really has this permission you need to hold
* the synch_lock when you read this value */
thread_synch_permission_t synch_perm;
/* Only valid while holding all_threads_synch_lock and thread_initexit_lock. Set
* to whether synch_with_all_threads was successful in synching this thread.
*/
bool synch_with_success;
/* Case 10101: allows threads waiting_at_safe_spot() to set their own
* contexts. This use sometimes requires a full os-specific context, which
* we hide behind a generic pointer and a size.
*/
priv_mcontext_t *set_mcontext;
void *set_context;
size_t set_context_size;
#ifdef X64
/* PR 263338: we have to pad for alignment */
byte *set_context_alloc;
#endif
} thread_synch_data_t;
/* This lock prevents more than one thread from being in the synch_with_all_
* threads method body at the same time (which would lead to deadlock as they
* tried to synchronize with each other)
*/
DECLARE_CXTSWPROT_VAR(mutex_t all_threads_synch_lock,
INIT_LOCK_FREE(all_threads_synch_lock));
/* pass either mc or both cxt and cxt_size */
static void
free_setcontext(priv_mcontext_t *mc, void *cxt, size_t cxt_size _IF_X64(byte *cxt_alloc))
{
if (mc != NULL) {
ASSERT(cxt == NULL);
global_heap_free(mc, sizeof(*mc) HEAPACCT(ACCT_OTHER));
} else if (cxt != NULL) {
ASSERT(cxt_size > 0);
global_heap_free(IF_X64_ELSE(cxt_alloc, cxt), cxt_size HEAPACCT(ACCT_OTHER));
}
}
static void
synch_thread_free_setcontext(thread_synch_data_t *tsd)
{
free_setcontext(tsd->set_mcontext, tsd->set_context, tsd->set_context_size
_IF_X64(tsd->set_context_alloc));
tsd->set_mcontext = NULL;
tsd->set_context = NULL;
}
void
synch_init(void)
{
}
void
synch_exit(void)
{
DELETE_LOCK(all_threads_synch_lock);
}
void
synch_thread_init(dcontext_t *dcontext)
{
thread_synch_data_t *tsd = (thread_synch_data_t *)
heap_alloc(dcontext, sizeof(thread_synch_data_t) HEAPACCT(ACCT_OTHER));
dcontext->synch_field = (void *) tsd;
tsd->pending_synch_count = 0;
tsd->synch_perm = THREAD_SYNCH_NONE;
tsd->synch_with_success = false;
tsd->set_mcontext = NULL;
tsd->set_context = NULL;
/* the synch_lock is in unprotected memory so that check_wait_at_safe_spot
* can call the EXITING_DR hook before releasing it */
tsd->synch_lock = HEAP_TYPE_ALLOC(dcontext, spin_mutex_t, ACCT_OTHER,
UNPROTECTED);
ASSIGN_INIT_SPINMUTEX_FREE(*tsd->synch_lock, synch_lock);
}
void
synch_thread_exit(dcontext_t *dcontext)
{
thread_synch_data_t *tsd = (thread_synch_data_t *) dcontext->synch_field;
/* Could be waiting at safe spot when we detach or exit */
synch_thread_free_setcontext(tsd);
DELETE_SPINMUTEX(*tsd->synch_lock);
/* Note that we do need to free this in non-debug builds since, despite
* appearances, UNPROTECTED_LOCAL is acutally allocated on a global
* heap. */
HEAP_TYPE_FREE(dcontext, tsd->synch_lock, spin_mutex_t, ACCT_OTHER,
UNPROTECTED);
#ifdef DEBUG
/* for non-debug we do fast exit path and don't free local heap */
/* clean up tsd fields here */
heap_free(dcontext, tsd, sizeof(thread_synch_data_t) HEAPACCT(ACCT_OTHER));
#endif
}
/* Check for a no-xfer permission. Currently used only for case 6821,
* where we need to distinguish three groups: unsafe (wait for safe
* point), safe and translatable, and safe but not translatable.
*/
bool
thread_synch_state_no_xfer(dcontext_t *dcontext)
{
thread_synch_data_t *tsd = (thread_synch_data_t *) dcontext->synch_field;
return (tsd->synch_perm == THREAD_SYNCH_NO_LOCKS_NO_XFER ||
tsd->synch_perm == THREAD_SYNCH_VALID_MCONTEXT_NO_XFER);
}
/* Only valid while holding all_threads_synch_lock and thread_initexit_lock. Set to
* whether synch_with_all_threads was successful in synching this thread.
* Cannot be called when THREAD_SYNCH_*_AND_CLEANED was requested as the
* thread-local memory will be freed on success!
*/
bool
thread_synch_successful(thread_record_t *tr)
{
thread_synch_data_t *tsd;
ASSERT(tr != NULL && tr->dcontext != NULL);
ASSERT_OWN_MUTEX(true, &all_threads_synch_lock);
ASSERT_OWN_MUTEX(true, &thread_initexit_lock);
tsd = (thread_synch_data_t *) tr->dcontext->synch_field;
return tsd->synch_with_success;
}
bool
is_at_do_syscall(dcontext_t *dcontext, app_pc pc, byte *esp)
{
app_pc buf[2];
bool res = safe_read(esp, sizeof(buf), buf);
if (!res) {
ASSERT(res); /* we expect the stack to always be readable */
return false;
}
if (does_syscall_ret_to_callsite()) {
#ifdef WINDOWS
if (get_syscall_method() == SYSCALL_METHOD_INT && DYNAMO_OPTION(sygate_int)) {
return (pc == after_do_syscall_addr(dcontext) &&
buf[0] == after_do_syscall_code(dcontext));
} else {
return pc == after_do_syscall_code(dcontext);
}
#else
return is_after_do_syscall_addr(dcontext, pc);
#endif
} else if (get_syscall_method() == SYSCALL_METHOD_SYSENTER) {
#ifdef WINDOWS
if (pc == vsyscall_after_syscall) {
if (DYNAMO_OPTION(sygate_sysenter))
return buf[1] == after_do_syscall_code(dcontext);
else
return buf[0] == after_do_syscall_code(dcontext);
} else {
/* not at a system call, could still have tos match after_do_syscall
* either by chance or because we leak that value on the apps stack
* (a non transparency) */
ASSERT_CURIOSITY(buf[0] != after_do_syscall_code(dcontext));
return false;
}
#else
/* Even when the main syscall method is sysenter, we also have a
* do_int_syscall and do_clone_syscall that use int, so check both.
* Note that we don't modify the stack, so once we do sysenter syscalls
* inlined in the cache (PR 288101) we'll need some mechanism to
* distinguish those: but for now if a sysenter instruction is used it
* has to be do_syscall since DR's own syscalls are ints.
*/
return (pc == vsyscall_sysenter_return_pc ||
is_after_do_syscall_addr(dcontext, pc));
#endif
}
/* we can reach here w/ a fault prior to 1st syscall on Linux */
IF_WINDOWS(ASSERT_NOT_REACHED());
return false;
}
/* Helper function for at_safe_spot(). Note state for client-owned threads isn't
* considered valid since it may be holding client locks and doesn't correspond to
* an actual app state. Caller should handle client-owned threads appropriately. */
static bool
is_native_thread_state_valid(dcontext_t *dcontext, app_pc pc, byte *esp)
{
/* ref case 3675, the assumption is that if we aren't executing
* out of dr memory and our stack isn't in dr memory (to disambiguate
* pc in kernel32, ntdll etc.) then the app has a valid native context.
* However, we can't call is_dynamo_address() as it (and its children)
* grab too many different locks, all of which we would have to check
* here in the same manner as fcache_unit_areas.lock in at_safe_spot(). So
* instead we just check the pc for the dr dll, interception code, and
* do_syscall regions and check the stack against the thread's dr stack
* and the initstack, all of which we can do without grabbing any locks.
* That should be sufficient at this point, FIXME try to use something
* like is_dynamo_address() to make this more maintainable */
/* For sysenter system calls we also have to check the top of the stack
* for the after_do_syscall_address to catch the do_syscall @ syscall
* itself case. */
ASSERT(esp != NULL);
ASSERT(is_thread_currently_native(dcontext->thread_record));
#ifdef WINDOWS
if (pc == (app_pc) thread_attach_takeover) {
/* We are trying to take over this thread but it has not yet been
* scheduled. It was native, and can't hold any DR locks.
*/
return true;
}
#endif
return (!is_in_dynamo_dll(pc) &&
IF_WINDOWS(!is_part_of_interception(pc) &&)
(!in_generated_routine(dcontext, pc) ||
/* we allow native thread to be at do_syscall - for int syscalls the pc
* (syscall return point) will be in do_syscall (so in generated routine)
* xref case 9333 */
is_at_do_syscall(dcontext, pc, esp)) &&
!is_on_initstack(esp) &&
!is_on_dstack(dcontext, esp) &&
IF_CLIENT_INTERFACE(!is_in_client_lib(pc) &&)
/* xref PR 200067 & 222812 on client-owned native threads */
IF_CLIENT_INTERFACE(!IS_CLIENT_THREAD(dcontext) &&)
#ifdef HOT_PATCHING_INTERFACE
/* Shouldn't be in the middle of executing a hotp_only patch. The
* check for being in hotp_dll is WHERE_HOTPATCH because the patch can
* change esp.
*/
(dcontext->whereami != WHERE_HOTPATCH &&
/* dynamo dll check has been done */
!hotp_only_in_tramp(pc)) &&
#endif
true /* no effect, simplifies ifdef handling with && above */
);
}
/* Translates the context mcontext for the given thread trec. If
* restore_memory is true, also restores any memory values that were
* shifted (primarily due to clients). If restore_memory is true, the
* caller should always relocate the translated thread, as it may not
* execute properly if left at its current location (it could be in the
* middle of client code in the cache).
* If recreate_app_state() is called, f will be passed through to it.
*
* Like any instance where a thread_record_t is used by a thread other than its
* owner, the caller must hold the thread_initexit_lock to ensure that it
* remains valid.
* Requires thread trec is at_safe_spot().
*/
bool
translate_mcontext(thread_record_t *trec, priv_mcontext_t *mcontext,
bool restore_memory, fragment_t *f)
{
thread_synch_data_t *tsd = (thread_synch_data_t *) trec->dcontext->synch_field;
bool res;
recreate_success_t success;
bool native_translate = false;
ASSERT(tsd->pending_synch_count >= 0);
/* check if native thread */
if (is_thread_currently_native(trec)) {
/* running natively, no need to translate unless at do_syscall for an
* intercepted-via-trampoline syscall which we allow now for case 9333 */
#ifdef CLIENT_INTERFACE
if (IS_CLIENT_THREAD(trec->dcontext)) {
/* don't need to translate anything */
LOG(THREAD_GET, LOG_SYNCH, 1, "translate context, thread "TIDFMT" is client "
"thread, no translation needed\n", trec->id);
return true;
}
#endif
if (is_native_thread_state_valid(trec->dcontext, (app_pc)mcontext->pc,
(byte *)mcontext->xsp)) {
#ifdef WINDOWS
if ((app_pc)mcontext->pc == (app_pc) thread_attach_takeover) {
LOG(THREAD_GET, LOG_SYNCH, 1, "translate context, thread "TIDFMT" at "
"takeover point\n", trec->id);
thread_attach_translate(trec->dcontext, mcontext, restore_memory);
return true;
}
#endif
if (is_at_do_syscall(trec->dcontext, (app_pc)mcontext->pc,
(byte *)mcontext->xsp)) {
LOG(THREAD_GET, LOG_SYNCH, 1, "translate context, thread "TIDFMT" running "
"natively, at do_syscall so translation needed\n", trec->id);
native_translate = true;
} else {
LOG(THREAD_GET, LOG_SYNCH, 1, "translate context, thread "TIDFMT" running "
"natively, no translation needed\n", trec->id);
return true;
}
} else {
/* now that do_syscall is a safe spot for native threads we shouldn't get
* here for get context on self, FIXME - is however possible to get here
* via get_context on unsuspended thread (result of which is technically
* undefined according to MS), see get_context post sys comments
* (should prob. synch there in which case can assert here) */
ASSERT(trec->id != get_thread_id());
ASSERT_CURIOSITY(false && "translate failure, likely get context on "
"unsuspended native thread");
/* we'll just try to translate and hope for the best */
native_translate = true;
}
}
if (!native_translate) {
/* check if waiting at a good spot */
spinmutex_lock(tsd->synch_lock);
res = THREAD_SYNCH_SAFE(tsd->synch_perm, THREAD_SYNCH_VALID_MCONTEXT);
spinmutex_unlock(tsd->synch_lock);
if (res) {
LOG(THREAD_GET, LOG_SYNCH, 1, "translate context, thread "TIDFMT" waiting at "
"valid mcontext point, copying over\n", trec->id);
DOLOG(2, LOG_SYNCH, {
LOG(THREAD_GET, LOG_SYNCH, 2, "Thread State\n");
dump_mcontext(get_mcontext(trec->dcontext), THREAD_GET, DUMP_NOT_XML);
});
*mcontext = *get_mcontext(trec->dcontext);
return true;
}
}
/* In case 4148 we see a thread calling NtGetContextThread on itself, which
* is undefined according to MS but it does get the syscall address, so it's
* fine with us. For other threads the app shouldn't be asking about them
* unless they're suspended, and the same goes for us.
*/
ASSERT_CURIOSITY(trec->dcontext->whereami == WHERE_FCACHE ||
native_translate ||
trec->id == get_thread_id());
LOG(THREAD_GET, LOG_SYNCH, 2,
"translate context, thread "TIDFMT" at pc_recreatable spot translating\n",
trec->id);
success = recreate_app_state(trec->dcontext, mcontext, restore_memory, f);
if (success != RECREATE_SUCCESS_STATE) {
/* should never happen right?
* actually it does when deciding whether can deliver a signal
* immediately (PR 213040).
*/
LOG(THREAD_GET, LOG_SYNCH, 1,
"translate context, thread "TIDFMT" unable to translate context at pc"
" = "PFX"\n", trec->id, mcontext->pc);
SYSLOG_INTERNAL_WARNING_ONCE("failed to translate");
return false;
}
return true;
}
static bool
waiting_at_safe_spot(thread_record_t *trec, thread_synch_state_t desired_state)
{
thread_synch_data_t *tsd = (thread_synch_data_t *) trec->dcontext->synch_field;
ASSERT(tsd->pending_synch_count >= 0);
/* check if waiting at a good spot, note that we can't spin in
* case the suspended thread is holding this lock, note only need
* lock to check the synch_perm */
if (spinmutex_trylock(tsd->synch_lock)) {
bool res = THREAD_SYNCH_SAFE(tsd->synch_perm, desired_state);
spinmutex_unlock(tsd->synch_lock);
if (res) {
LOG(THREAD_GET, LOG_SYNCH, 2,
"thread "TIDFMT" waiting at safe spot\n", trec->id);
return true;
}
} else {
LOG(THREAD_GET, LOG_SYNCH, 2,
"at_safe_spot unable to get locks to test if thread "TIDFMT" is waiting "
"at safe spot\n", trec->id);
}
return false;
}
#ifdef CLIENT_SIDELINE
static bool
should_suspend_client_thread(dcontext_t *dcontext, thread_synch_state_t desired_state)
{
/* Marking un-suspendable does not apply to cleaning/terminating */
ASSERT(IS_CLIENT_THREAD(dcontext));
return (THREAD_SYNCH_IS_CLEANED(desired_state) ||
dcontext->client_data->suspendable);
}
#endif
/* checks whether the thread trec is at a spot suitable for requested define
* desired_state
* Requires that trec thread is suspended */
/* Note that since trec is potentially suspended at an arbitrary point,
* this function (and any function it calls) cannot call mutex_lock as
* trec thread may hold a lock. It is ok for at_safe_spot to return false if
* it can't obtain a lock on the first try. FIXME : in the long term we may
* want to go to a locking model that stores the thread id of the owner in
* which case we can check for this situation directly
*/
bool
at_safe_spot(thread_record_t *trec, priv_mcontext_t *mc,
thread_synch_state_t desired_state)
{
bool safe = false;
if (waiting_at_safe_spot(trec, desired_state))
return true;
/* check if suspended at good spot */
/* FIXME: right now don't distinguish between suspend and term privileges
* even though suspend is stronger requirement, are the checks below
* sufficient */
/* FIXME : check with respect to flush, should be ok */
/* test fcache_unit_areas.lock (from fcache.c) before calling recreate_app_state
* since it calls in_fcache() which uses the lock (if we are in_fcache()
* assume other locks are not a problem (so is_dynamo_address is fine)) */
/* Right now the only dr code that ends up in the cache is our DLL main
* (which we'll reduce/get rid of with libc independence), our takeover
* from preinject return stack, and the callback.c interception code.
* FIXME : test for just these and ASSERT(!is_dynamo_address) otherwise */
if (is_thread_currently_native(trec)) {
/* thread is running native, verify is not in dr code */
#ifdef CLIENT_INTERFACE
/* We treat client-owned threads (such as a client nudge thread) as native and
* consider them safe if they are in the client_lib. Since they might own client
* locks that could block application threads from progressing, we synchronize
* with them last. FIXME - xref PR 231301 - since we can't disambiguate
* client->ntdll/gencode which is safe from client->dr->ntdll/gencode which isn't
* we disallow both. This could hurt synchronization efficiency if the client
* owned thread spent most of its execution time calling out of its lib to ntdll
* routines or generated code. */
if (IS_CLIENT_THREAD(trec->dcontext)) {
safe = (trec->dcontext->client_data->client_thread_safe_for_synch ||
is_in_client_lib(mc->pc)) &&
/* Do not cleanup/terminate a thread holding a client lock (PR 558463) */
/* Actually, don't consider a thread holding a client lock to be safe
* at all (PR 609569): client should use
* dr_client_thread_set_suspendable(false) if its thread spends a lot
* of time holding locks.
*/
(!should_suspend_client_thread(trec->dcontext, desired_state) ||
trec->dcontext->client_data->mutex_count == 0);
}
#endif
if (is_native_thread_state_valid(trec->dcontext, mc->pc,
(byte *)mc->xsp)) {
safe = true;
/* We should always be able to translate a valid native state, but be
* sure to check before thread_attach_exit().
*/
ASSERT(translate_mcontext(trec, mc, false/*just querying*/, NULL));
#ifdef WINDOWS
if (mc->pc == (app_pc) thread_attach_takeover &&
THREAD_SYNCH_IS_CLEANED(desired_state)) {
/* The takeover data will be freed at process exit, but we might
* clean up a thread mid-run, so make sure we free the data.
*/
thread_attach_exit(trec->dcontext, mc);
}
#endif
}
#ifdef CLIENT_INTERFACE
} else if (desired_state == THREAD_SYNCH_TERMINATED_AND_CLEANED &&
trec->dcontext->whereami == WHERE_FCACHE &&
trec->dcontext->client_data->at_safe_to_terminate_syscall) {
/* i#1420: At safe to terminate syscall like dr_sleep in a clean call.
* XXX: A thread in dr_sleep might not be safe to terminate for some
* corner cases: for example, a client may hold a lock and then go sleep,
* terminating it may mess the client up for not releasing the lock.
* We limit this to the thread being in fcache (i.e., from a clean call)
* to rule out some corner cases.
*/
safe = true;
#endif
} else if ((!WRITE_LOCK_HELD(&fcache_unit_areas->lock) &&
/* even though we only need the read lock, if our target holds it
* and a 3rd thread requests the write lock, we'll hang if we
* ask for the read lock (case 7493)
*/
!READ_LOCK_HELD(&fcache_unit_areas->lock)) &&
recreate_app_state(trec->dcontext, mc, false/*just query*/, NULL) ==
RECREATE_SUCCESS_STATE &&
/* is ok to call is_dynamo_address even though it grabs many
* locks because recreate_app_state succeeded */
!is_dynamo_address(mc->pc)) {
safe = true;
}
if (safe) {
ASSERT(trec->dcontext->whereami == WHERE_FCACHE ||
is_thread_currently_native(trec));
LOG(THREAD_GET, LOG_SYNCH, 2,
"thread "TIDFMT" suspended at safe spot pc="PFX"\n", trec->id, mc->pc);
return true;
}
LOG(THREAD_GET, LOG_SYNCH, 2,
"thread "TIDFMT" not at safe spot (pc="PFX") for %d\n",
trec->id, mc->pc, desired_state);
return false;
}
/* a fast way to tell a thread if it should call check_wait_at_safe_spot
* if translating context would be expensive */
bool
should_wait_at_safe_spot(dcontext_t *dcontext)
{
thread_synch_data_t *tsd = (thread_synch_data_t *) dcontext->synch_field;
return (tsd->pending_synch_count != 0);
}
/* use with care! normally check_wait_at_safe_spot() should be called instead */
void
set_synch_state(dcontext_t *dcontext, thread_synch_permission_t state)
{
thread_synch_data_t *tsd = (thread_synch_data_t *) dcontext->synch_field;
spinmutex_lock(tsd->synch_lock);
tsd->synch_perm = state;
spinmutex_unlock(tsd->synch_lock);
}
/* checks to see if any threads are waiting to synch with this one and waits
* if they are
* cur_state - a given permission define from above that describes the current
* state of the caller
* NOTE - Requires the caller is !could_be_linking (i.e. not in an
* enter_couldbelinking state)
*/
void
check_wait_at_safe_spot(dcontext_t *dcontext, thread_synch_permission_t cur_state)
{
thread_synch_data_t *tsd = (thread_synch_data_t *) dcontext->synch_field;
app_pc pc;
byte cxt[MAX(CONTEXT_HEAP_SIZE_OPAQUE, sizeof(priv_mcontext_t))];
bool set_context = false;
bool set_mcontext = false;
if (tsd->pending_synch_count == 0 || cur_state == THREAD_SYNCH_NONE)
return;
ASSERT(tsd->pending_synch_count >= 0);
pc = get_mcontext(dcontext)->pc;
LOG(THREAD, LOG_SYNCH, 2,
"waiting for synch with state %d (pc "PFX")\n",
cur_state, pc);
if (cur_state == THREAD_SYNCH_VALID_MCONTEXT) {
ASSERT(!is_dynamo_address(pc));
/* for detach must set this here and now */
IF_WINDOWS(IF_CLIENT_INTERFACE(set_last_error(dcontext->app_errno)));
}
spinmutex_lock(tsd->synch_lock);
tsd->synch_perm = cur_state;
/* Since can be killed, suspended, etc. must call the exit dr hook. But, to
* avoid races, we must do so before giving up the synch_lock. This is why
* that lock has to be in unprotected memory. FIXME - for single thread in
* dr this will lead to rank order violation between dr exclusivity lock
* and the synch_lock with no easy workaround (real deadlocks possible).
* Luckily we'll prob. never use that option. */
if (INTERNAL_OPTION(single_thread_in_DR)) {
ASSERT_NOT_IMPLEMENTED(false);
}
EXITING_DR();
/* Ref case 5074, for us/app to successfully SetThreadContext at
* this synch point, this thread can NOT be at a system call. So, for
* case 10101, we instead have threads that are waiting_at_safe_spot()
* set their own contexts, allowing us to make system calls here.
* We don't yet handle the detach case, so it still requires no system
* calls, including the act of releasing the synch_lock
* which is why that lock has to be a user mode spin yield lock.
* FIXME: we could change tsd->synch_lock back to a regular lock
* once we have detach handling system calls here.
*/
spinmutex_unlock(tsd->synch_lock);
while (tsd->pending_synch_count > 0 &&
tsd->synch_perm != THREAD_SYNCH_NONE) {
STATS_INC_DC(dcontext, synch_loops_wait_safe);
#ifdef WINDOWS
if (doing_detach) {
/* We spin for any non-detach synchs encountered during detach
* since we have no flag telling us this synch is for detach. */
/* Ref case 5074, can NOT use os_thread_yield here. This must be a user
* mode spin loop. */
SPINLOCK_PAUSE();
} else {
#endif
/* FIXME case 10100: replace this sleep/yield with a wait_for_event() */
synch_thread_yield();
#ifdef WINDOWS
}
#endif
}
/* Regain the synch_lock before ENTERING_DR to avoid races with getting
* suspended/killed in the middle of ENTERING_DR (before synch_perm is
* reset to NONE). */
/* Ref case 5074, for detach we still can NOT use os_thread_yield here (no system
* calls) so don't allow the spinmutex_lock to yield while grabbing the lock. */
spinmutex_lock_no_yield(tsd->synch_lock);
ENTERING_DR();
tsd->synch_perm = THREAD_SYNCH_NONE;
if (tsd->set_mcontext != NULL || tsd->set_context != NULL) {
IF_WINDOWS(ASSERT(!doing_detach));
/* Make a local copy */
ASSERT(CONTEXT_HEAP_SIZE_OPAQUE >= sizeof(priv_mcontext_t));
if (tsd->set_mcontext != NULL) {
set_mcontext = true;
memcpy(cxt, tsd->set_mcontext, sizeof(*tsd->set_mcontext));
} else {
set_context = true;
memcpy(cxt, tsd->set_context, tsd->set_context_size);
}
synch_thread_free_setcontext(tsd); /* sets to NULL for us */
}
spinmutex_unlock(tsd->synch_lock);
LOG(THREAD, LOG_SYNCH, 2,
"done waiting for synch with state %d (pc "PFX")\n",
cur_state, pc);
if (set_mcontext || set_context) {
/* FIXME: see comment in dispatch.c check_wait_at_safe_spot() call
* about problems with KSTART(fcache_* differences bet the target
* being at the synch point vs in the cache.
*/
if (set_mcontext)
thread_set_self_mcontext((priv_mcontext_t *)cxt);
else
thread_set_self_context((void *)cxt);
ASSERT_NOT_REACHED();
}
}
/* adjusts the pending synch count */
void
adjust_wait_at_safe_spot(dcontext_t *dcontext, int amt)
{
thread_synch_data_t *tsd = (thread_synch_data_t *) dcontext->synch_field;
ASSERT(tsd->pending_synch_count >= 0);
spinmutex_lock(tsd->synch_lock);
ATOMIC_ADD(int, tsd->pending_synch_count, amt);
spinmutex_unlock(tsd->synch_lock);
}
/* Case 10101: Safely sets the context for a target thread that may be waiting at a
* safe spot, in which case we do not want to directly do a setcontext as the return
* from the yield or wait system call will mess up the state (case 5074).
* Assumes that cxt was allocated on the global heap, and frees it, rather than
* making its own copy (as an optimization).
* Does not work on the executing thread.
* Caller must hold thread_initexit_lock.
* If used on behalf of the app, it's up to the caller to check for privileges.
*/
bool
set_synched_thread_context(thread_record_t *trec,
/* pass either mc or both cxt and cxt_size */
priv_mcontext_t *mc, void *cxt, size_t cxt_size,
thread_synch_state_t desired_state
_IF_X64(byte *cxt_alloc)
_IF_WINDOWS(NTSTATUS *status/*OUT*/))
{
bool res = true;
ASSERT(trec != NULL && trec->dcontext != NULL);
ASSERT(trec->dcontext != get_thread_private_dcontext());
ASSERT_OWN_MUTEX(true, &thread_initexit_lock);
#ifdef WINDOWS
if (status != NULL)
*status = STATUS_SUCCESS;
#endif
if (waiting_at_safe_spot(trec, desired_state)) {
/* case 10101: to allow system calls in check_wait_at_safe_spot() for
* performance reasons we have the waiting thread perform its own setcontext.
*/
thread_synch_data_t *tsd = (thread_synch_data_t *) trec->dcontext->synch_field;
spinmutex_lock(tsd->synch_lock);
if (tsd->set_mcontext != NULL || tsd->set_context != NULL) {
/* Two synchs in a row while still waiting; 2nd takes precedence */
STATS_INC(wait_multiple_setcxt);
synch_thread_free_setcontext(tsd);
}
LOG(THREAD_GET, LOG_SYNCH, 2,
"set_synched_thread_context %d to pc "PFX" via %s\n", trec->id,
(mc != NULL) ? mc->pc : (app_pc)
IF_WINDOWS_ELSE(((CONTEXT*)cxt)->CXT_XIP,
((sigcontext_t *)cxt)->SC_XIP),
(mc != NULL) ? "mc" : "CONTEXT");
if (mc != NULL)
tsd->set_mcontext = mc;
else {
ASSERT(cxt != NULL && cxt_size > 0);
tsd->set_context = cxt;
tsd->set_context_size = cxt_size;
}
IF_X64(tsd->set_context_alloc = cxt_alloc);
ASSERT(THREAD_SYNCH_SAFE(tsd->synch_perm, desired_state));
ASSERT(tsd->pending_synch_count >= 0);
/* Don't need to change pending_synch_count or anything; when thread is
* resumed it will properly reset everything itself */
spinmutex_unlock(tsd->synch_lock);
} else {
if (mc != NULL) {
res = thread_set_mcontext(trec, mc);
} else {
#ifdef WINDOWS
/* sort of ugly: but NtSetContextThread handling needs the status */
if (status != NULL) {
*status = nt_set_context(trec->handle, (CONTEXT *) cxt);
res = NT_SUCCESS(*status);
} else
res = thread_set_context(trec->handle, (CONTEXT *) cxt);
#else
/* currently there are no callers who don't pass mc: presumably
* PR 212090 will change that */
ASSERT_NOT_IMPLEMENTED(false);
#endif
}
free_setcontext(mc, cxt, cxt_size _IF_X64(cxt_alloc));
}
return res;
}
/* This is used to limit the maximum number of times synch_with_thread or
* synch_with_all_threads spin yield loops while waiting on an exiting thread.
* We assert if we ever break out of the loop because of this limit. FIXME make
* sure this limit is large enough that if it does ever trigger it's because
* of some kind of deadlock situation. Breaking out of the synchronization loop
* early is a correctness issue. Right now the limits are large but arbitrary.
* FIXME : once we are confident about thread synch get rid of these max loop checks.
* N.B.: the THREAD_SYNCH_SMALL_LOOP_MAX flag causes us to divide these by 10.
*/
#define SYNCH_ALL_THREADS_MAXIMUM_LOOPS (DYNAMO_OPTION(synch_all_threads_max_loops))
#define SYNCH_MAXIMUM_LOOPS (DYNAMO_OPTION(synch_thread_max_loops))
/* Amt of time in ms to wait for threads to get to a safe spot per a loop,
* see comments in synch_with_yield() on value. Our default value is 5ms which,
* depending on the tick resolution could end up being as long as 10 ms. */
#define SYNCH_WITH_WAIT_MS ((int)DYNAMO_OPTION(synch_with_sleep_time))
/* for use by synch_with_* routines to wait for thread(s) */
static void
synch_thread_yield()
{
/* xref 9400, 9488 - os_thread_yield() works ok on an UP machine, but on an MP machine
* yield might not actually do anything (in which case we burn through to the max
* loop counts pretty quick). We actually do want to wait a reasonable amt of time
* since the target thread might be doing some long latency dr operation (like
* dumping 500kb of registry into a forensics file) so we have the option to sleep
* instead. */
uint num_procs = get_num_processors();
ASSERT(num_procs != 0);
if ((num_procs == 1 && DYNAMO_OPTION(synch_thread_sleep_UP)) ||
(num_procs > 1 && DYNAMO_OPTION(synch_thread_sleep_MP))) {
os_thread_sleep(SYNCH_WITH_WAIT_MS);
} else {
os_thread_yield();
}
}
/* returns a thread_synch_result_t value
* id - the thread you want to synch with
* block - whether or not should spin until synch is successful
* hold_initexit_lock - whether or not the caller holds the thread_initexit_lock
* caller_state - a given permission define from above that describes the
* current state of the caller (note that holding the initexit
* lock is ok with respect to NO_LOCK
* desired_state - a requested state define from above that describes the
* desired synchronization
* flags - options from THREAD_SYNCH_ bitmask values
* NOTE - if you hold the initexit_lock and block with greater than NONE for
* caller state, then initexit_lock may be released and re-acquired
* NOTE - if any of the nt_ routines fails, it is assumed the thread no longer
* exists and returns true
* NOTE - if called directly (i.e. not through synch_with_all_threads)
* requires THREAD_SYNCH_IS_SAFE(caller_state, desired_state) to avoid deadlock
* NOTE - Requires the caller is !could_be_linking (i.e. not in an
* enter_couldbelinking state)
* NOTE - you can't call this with a thread that you've already suspended
*/
thread_synch_result_t
synch_with_thread(thread_id_t id, bool block, bool hold_initexit_lock,
thread_synch_permission_t caller_state,
thread_synch_state_t desired_state,
uint flags)
{
thread_id_t my_id = get_thread_id();
uint loop_count = 0;
int expect_exiting = 0;
thread_record_t *my_tr = thread_lookup(my_id), *trec = NULL;
dcontext_t *dcontext = NULL;
priv_mcontext_t mc;
thread_synch_result_t res = THREAD_SYNCH_RESULT_NOT_SAFE;
bool first_loop = true;
IF_UNIX(bool actually_suspended = true;)
const uint max_loops = TEST(THREAD_SYNCH_SMALL_LOOP_MAX, flags) ?
(SYNCH_MAXIMUM_LOOPS/10) : SYNCH_MAXIMUM_LOOPS;
ASSERT(id != my_id);
/* Must set ABORT or IGNORE. Only caller can RETRY as need a new
* set of threads for that, hoping problematic one is short-lived.
*/
ASSERT(TESTANY(THREAD_SYNCH_SUSPEND_FAILURE_ABORT |
THREAD_SYNCH_SUSPEND_FAILURE_IGNORE, flags) &&
!TESTALL(THREAD_SYNCH_SUSPEND_FAILURE_ABORT |
THREAD_SYNCH_SUSPEND_FAILURE_IGNORE, flags));
if (my_tr != NULL) {
dcontext = my_tr->dcontext;
expect_exiting = dcontext->is_exiting ? 1 : 0;
ASSERT(exiting_thread_count >= expect_exiting);
} else {
/* calling thread should always be a known thread */
ASSERT_NOT_REACHED();
}
LOG(THREAD, LOG_SYNCH, 2,
"Synching with thread "TIDFMT", giving %d, requesting %d, blocking=%d\n",
id, caller_state, desired_state, block);
if (!hold_initexit_lock)
mutex_lock(&thread_initexit_lock);
while (true) {
/* get thread record */
/* FIXME : thread id recycling is possible that this could be a
* different thread, perhaps we should take handle instead of id
* FIXME: use the new num field of thread_record_t?
*/
LOG(THREAD, LOG_SYNCH, 3,
"Looping on synch with thread "TIDFMT"\n", id);
trec = thread_lookup(id);
/* We test the exiting thread count to avoid races between terminate/
* suspend thread (current thread, though we could be here for other
* reasons) and an exiting thread (who might no longer be on the all
* threads list) who is still using shared resources (ref case 3121) */
if ((trec == NULL && exiting_thread_count == expect_exiting)
|| loop_count++ > max_loops) {
/* make sure we didn't exit the loop without synchronizing, FIXME :
* in release builds we assume the synchronization is failing and
* continue without it, but that is dangerous.
* It is now up to the caller to handle this, and some use
* small loop counts and abort on failure, so only a curiosity. */
ASSERT_CURIOSITY(loop_count < max_loops);
LOG(THREAD, LOG_SYNCH, 3,
"Exceeded loop count synching with thread "TIDFMT"\n", id);
goto exit_synch_with_thread;
}
DOSTATS({
if (trec == NULL && exiting_thread_count > expect_exiting) {
LOG(THREAD, LOG_SYNCH, 2, "Waiting for an exiting thread\n");
STATS_INC(synch_yields_for_exiting_thread);
}
});
#ifdef UNIX
if (trec != NULL && trec->execve) {
/* i#237/PR 498284: clean up vfork "threads" that invoked execve.
* There should be no race since vfork suspends the parent.
*/
res = THREAD_SYNCH_RESULT_SUCCESS;
actually_suspended = false;
break;
}
#endif
if (trec != NULL) {
if (first_loop) {
adjust_wait_at_safe_spot(trec->dcontext, 1);
first_loop = false;
}
if (!os_thread_suspend(trec)) {
/* FIXME : eventually should be a real assert once we figure out
* how to handle threads with low privilege handles */
ASSERT_CURIOSITY_ONCE(false && "Thead synch unable to suspend target"
" thread, case 2096?");
res = (TEST(THREAD_SYNCH_SUSPEND_FAILURE_IGNORE, flags) ?
THREAD_SYNCH_RESULT_SUCCESS : THREAD_SYNCH_RESULT_SUSPEND_FAILURE);
IF_UNIX(actually_suspended = false);
break;
}
if (!thread_get_mcontext(trec, &mc)) {
/* FIXME : eventually should be a real assert once we figure out
* how to handle threads with low privilege handles */
ASSERT_CURIOSITY_ONCE(false && "Thead synch unable to get_context target"
" thread, case 2096?");
res = (TEST(THREAD_SYNCH_SUSPEND_FAILURE_IGNORE, flags) ?
THREAD_SYNCH_RESULT_SUCCESS : THREAD_SYNCH_RESULT_SUSPEND_FAILURE);
/* Make sure to not leave suspended if not returning success */
if (!TEST(THREAD_SYNCH_SUSPEND_FAILURE_IGNORE, flags))
os_thread_resume(trec);
break;
}
if (at_safe_spot(trec, &mc, desired_state)) {
/* FIXME: case 5325 for detach handling and testing */
IF_WINDOWS(ASSERT_NOT_IMPLEMENTED
(!dcontext->aslr_context.sys_aslr_clobbered));
LOG(THREAD, LOG_SYNCH, 2,
"Thread "TIDFMT" suspended in good spot\n", id);
LOG(trec->dcontext->logfile, LOG_SYNCH, 2,
"@@@@@@@@@@@@@@@@@@ SUSPENDED BY THREAD "TIDFMT" synch_with_thread "
"@@@@@@@@@@@@@@@@@@\n", my_id);
res = THREAD_SYNCH_RESULT_SUCCESS;
break;
}
if (!os_thread_resume(trec)) {
ASSERT_NOT_REACHED();
res = (TEST(THREAD_SYNCH_SUSPEND_FAILURE_IGNORE, flags) ?
THREAD_SYNCH_RESULT_SUCCESS : THREAD_SYNCH_RESULT_SUSPEND_FAILURE);
break;
}
}
/* don't loop if !block, before we ever release initexit_lock in case
* caller is holding it and not blocking, (i.e. wants to keep it) */
if (!block)
break;
/* see if someone is waiting for us */
if (dcontext != NULL && caller_state != THREAD_SYNCH_NONE &&
should_wait_at_safe_spot(dcontext)) {
if (trec != NULL)
adjust_wait_at_safe_spot(trec->dcontext, -1);
mutex_unlock(&thread_initexit_lock);
/* ref case 5552, if we've inc'ed the exiting thread count need to
* adjust it back before calling check_wait_at_safe_spot since we
* may end up being killed there */
if (dcontext->is_exiting) {
ASSERT(exiting_thread_count >= 1);
ATOMIC_DEC(int, exiting_thread_count);
}
check_wait_at_safe_spot(dcontext, caller_state);
if (dcontext->is_exiting) {
ATOMIC_INC(int, exiting_thread_count);
}
mutex_lock(&thread_initexit_lock);
trec = thread_lookup(id);
/* Like above, we test the exiting thread count to avoid races
* between terminate/suspend thread (current thread, though we
* could be here for other reasons) and an exiting thread (who
* might no longer be on the all threads list) who is still using
* shared resources (ref case 3121) */
if (trec == NULL && exiting_thread_count == expect_exiting) {
if (!hold_initexit_lock)
mutex_unlock(&thread_initexit_lock);
return THREAD_SYNCH_RESULT_SUCCESS;
}
DOSTATS({
if (trec == NULL && exiting_thread_count > expect_exiting) {
LOG(THREAD, LOG_SYNCH, 2, "Waiting for an exiting thread\n");
STATS_INC(synch_yields_for_exiting_thread);
}
});
if (trec != NULL)
adjust_wait_at_safe_spot(trec->dcontext, 1);
}
STATS_INC(synch_yields);
mutex_unlock(&thread_initexit_lock);
/* Note - we only need call the ENTER/EXIT_DR hooks if single thread
* in dr since we are not really exiting DR here (we just need to give
* up the exclusion lock for a while to let thread we are trying to
* synch with make progress towards a safe synch point). */
if (INTERNAL_OPTION(single_thread_in_DR))
EXITING_DR(); /* give up DR exclusion lock */
synch_thread_yield();
if (INTERNAL_OPTION(single_thread_in_DR))
ENTERING_DR(); /* re-gain DR exclusion lock */
mutex_lock(&thread_initexit_lock);
}
/* reset this back to before */
adjust_wait_at_safe_spot(trec->dcontext, -1);
/* success!, is suspended (or already exited) put in desired state */
if (res == THREAD_SYNCH_RESULT_SUCCESS) {
LOG(THREAD, LOG_SYNCH, 2,
"Success synching with thread "TIDFMT" performing cleanup\n", id);
if (THREAD_SYNCH_IS_TERMINATED(desired_state)) {
if (IF_UNIX_ELSE(!trec->execve, true))
os_thread_terminate(trec);
#ifdef UNIX
/* We need to ensure the target thread has received the
* signal and is no longer using its sigstack or ostd struct
* before we clean those up.
*/
/* PR 452168: if failed to send suspend signal, do not spin */
if (actually_suspended) {
if (!is_thread_terminated(trec->dcontext)) {
/* i#96/PR 295561: use futex(2) if available. Blocks until
* the thread gets terminated.
*/
os_wait_thread_terminated(trec->dcontext);
}
} else
ASSERT(TEST(THREAD_SYNCH_SUSPEND_FAILURE_IGNORE, flags));
#endif
}
if (THREAD_SYNCH_IS_CLEANED(desired_state)) {
dynamo_other_thread_exit(trec _IF_WINDOWS(false));
}
}
exit_synch_with_thread:
if (!hold_initexit_lock)
mutex_unlock(&thread_initexit_lock);
return res;
}
/* desired_synch_state - a requested state define from above that describes
* the synchronization required
* threads, num_threads - must not be NULL, if !THREAD_SYNCH_IS_CLEANED(desired
* synch_state) then will hold a list and num of threads
* cur_state - a given permission from above that describes the state of the
* caller
* flags - options from THREAD_SYNCH_ bitmask values
* NOTE - Requires that the caller doesn't hold the thread_initexit_lock, on
* return caller will hold the thread_initexit_lock
* NOTE - Requires the caller is !could_be_linking (i.e. not in an
* enter_couldbelinking state)
* NOTE - To avoid deadlock this routine should really only be called with
* cur_state giving maximum permissions, (currently app_exit and detach could
* conflict, except our routes to app_exit go through different synch point
* (TermThread or TermProcess) first
* NOTE - when !all_synched, if desired_synch_state is not cleaned or synch result is
* ignored, the caller is reponsible for resuming threads that are suspended,
* freeing allocation for threads array and releasing locks
* Caller should call end_synch_with_all_threads when finished to accomplish that.
*/
bool
synch_with_all_threads(thread_synch_state_t desired_synch_state,
/*OUT*/ thread_record_t ***threads_out,
/*OUT*/ int *num_threads_out,
thread_synch_permission_t cur_state,
/* FIXME: turn the ThreadSynch* enums into bitmasks and merge
* into flags param */
uint flags)
{
/* Case 8815: we cannot use the OUT params themselves internally as they
* may be volatile, so we need our own values until we're ready to return
*/
thread_record_t **threads = NULL;
int num_threads = 0;
/* we record ids from before we gave up thread_initexit_lock */
thread_id_t *thread_ids_temp = NULL;
int num_threads_temp = 0, i, j, expect_exiting = 0;
/* synch array contains a SYNCH_WITH_ALL_ value for each thread */
uint *synch_array = NULL, *synch_array_temp = NULL;
enum {
SYNCH_WITH_ALL_NEW = 0,
SYNCH_WITH_ALL_NOTIFIED = 1,
SYNCH_WITH_ALL_SYNCHED = 2,
};
bool all_synched = false;
thread_id_t my_id = get_thread_id();
uint loop_count = 0;
thread_record_t *tr = thread_lookup(my_id);
dcontext_t *dcontext = NULL;
uint flags_one; /* flags for synch_with_thread() call */
thread_synch_result_t synch_res;
const uint max_loops = TEST(THREAD_SYNCH_SMALL_LOOP_MAX, flags) ?
(SYNCH_ALL_THREADS_MAXIMUM_LOOPS/10) : SYNCH_ALL_THREADS_MAXIMUM_LOOPS;
#ifdef CLIENT_INTERFACE
/* We treat client-owned threads as native but they don't have a clean native state
* for us to suspend them in (they are always in client or dr code). We need to be
* able to suspend such threads so that they're !couldbelinking and holding no dr
* locks. We make the assumption that client-owned threads that are in the client
* library (or are in a dr routine that has set dcontext->client_thread_safe_to_sync)
* meet this requirement (see at_safe_spot()). As such, all we need to worry about
* here are client locks the client-owned thread might hold that could block other
* threads from reaching safe spots. If we only suspend client-owned threads once
* all other threads are taken care of then this is not a problem. FIXME - xref
* PR 231301 on issues that arise if the client thread spends most of its time
* calling out of its lib to dr API, ntdll, or generated code functions. */
bool finished_non_client_threads;
#endif
ASSERT(!dynamo_all_threads_synched);
/* flag any caller who does not give up enough permissions to avoid livelock
* with other synch_with_all_threads callers
*/
ASSERT_CURIOSITY(cur_state >= THREAD_SYNCH_NO_LOCKS_NO_XFER);
/* also flag anyone asking for full mcontext w/o possibility of no_xfer,
* which can also livelock
*/
ASSERT_CURIOSITY(desired_synch_state < THREAD_SYNCH_SUSPENDED_VALID_MCONTEXT
/* detach currently violates this: bug 8942 */
IF_WINDOWS(|| doing_detach));
/* must set exactly one of these -- FIXME: better way to check? */
ASSERT(TESTANY(THREAD_SYNCH_SUSPEND_FAILURE_ABORT |
THREAD_SYNCH_SUSPEND_FAILURE_IGNORE |
THREAD_SYNCH_SUSPEND_FAILURE_RETRY, flags) &&
!TESTALL(THREAD_SYNCH_SUSPEND_FAILURE_ABORT |
THREAD_SYNCH_SUSPEND_FAILURE_IGNORE, flags) &&
!TESTALL(THREAD_SYNCH_SUSPEND_FAILURE_ABORT |
THREAD_SYNCH_SUSPEND_FAILURE_RETRY, flags) &&
!TESTALL(THREAD_SYNCH_SUSPEND_FAILURE_IGNORE |
THREAD_SYNCH_SUSPEND_FAILURE_RETRY, flags));
flags_one = flags;
/* we'll do the retry */
if (TEST(THREAD_SYNCH_SUSPEND_FAILURE_RETRY, flags)) {
flags_one &= ~THREAD_SYNCH_SUSPEND_FAILURE_RETRY;
flags_one |= THREAD_SYNCH_SUSPEND_FAILURE_ABORT;
}
if (tr != NULL) {
dcontext = tr->dcontext;
expect_exiting = dcontext->is_exiting ? 1 : 0;
ASSERT(exiting_thread_count >= expect_exiting);
} else {
/* calling thread should always be a known thread */
ASSERT_NOT_REACHED();
}
LOG(THREAD, LOG_SYNCH, 1,
"synch with all threads my id = "SZFMT
" Giving %d permission and seeking %d state\n",
my_id, cur_state, desired_synch_state);
/* grab all_threads_synch_lock */
/* since all_threads synch doesn't give any permissions this is necessary
* to prevent deadlock in the case of two threads trying to synch with all
* threads at the same time */
/* FIXME: for DEADLOCK_AVOIDANCE, to preserve LIFO, should we
* exit DR, trylock, then immediately enter DR? introducing any
* race conditions in doing so?
* Ditto on all other os_thread_yields in this file!
*/
while (!mutex_trylock(&all_threads_synch_lock)) {
LOG(THREAD, LOG_SYNCH, 2, "Spinning on all threads synch lock\n");
STATS_INC(synch_yields);
if (dcontext != NULL && cur_state != THREAD_SYNCH_NONE &&
should_wait_at_safe_spot(dcontext)) {
/* ref case 5552, if we've inc'ed the exiting thread count need to
* adjust it back before calling check_wait_at_safe_spot since we
* may end up being killed there */
if (dcontext->is_exiting) {
ASSERT(exiting_thread_count >= 1);
ATOMIC_DEC(int, exiting_thread_count);
}
check_wait_at_safe_spot(dcontext, cur_state);
if (dcontext->is_exiting) {
ATOMIC_INC(int, exiting_thread_count);
}
}
LOG(THREAD, LOG_SYNCH, 2, "Yielding on all threads synch lock\n");
/* Note - we only need call the ENTER/EXIT_DR hooks if single thread
* in dr since we are not really exiting DR here (we just need to give
* up the exclusion lock for a while to let thread we are trying to
* synch with make progress towards a safe synch point). */
if (INTERNAL_OPTION(single_thread_in_DR))
EXITING_DR(); /* give up DR exclusion lock */
os_thread_yield();
if (INTERNAL_OPTION(single_thread_in_DR))
ENTERING_DR(); /* re-gain DR exclusion lock */
}
mutex_lock(&thread_initexit_lock);
/* synch with all threads */
/* FIXME: this should be a do/while loop - then we wouldn't have
* to initialize all the variables above
*/
while ((!all_synched || exiting_thread_count > expect_exiting)
&& loop_count++ < max_loops) {
if (threads != NULL){
/* Case 8941: must free here rather than when yield (below) since
* termination condition can change between there and here
*/
ASSERT(num_threads > 0);
global_heap_free(threads, num_threads * sizeof(thread_record_t *)
HEAPACCT(ACCT_THREAD_MGT));
/* be paranoid */
threads = NULL;
num_threads = 0;
}
get_list_of_threads(&threads, &num_threads);
synch_array = (uint *)global_heap_alloc(num_threads * sizeof(uint)
HEAPACCT(ACCT_THREAD_MGT));
for (i = 0; i < num_threads; i++) {
synch_array[i] = SYNCH_WITH_ALL_NEW;
}
/* Fixme : an inefficient algorithm, but is not as bad as it seems
* since it is very unlikely that many threads have started or ended
* and the list threads routine always puts them in the same order
*/
/* on first loop num_threads_temp == 0 */
for (i = 0; i < num_threads_temp; i++) {
/* care only if we have already notified or synched thread */
if (synch_array_temp[i] != SYNCH_WITH_ALL_NEW) {
for (j = 0; j < num_threads; j++) {
/* FIXME : os recycles thread ids, should have stronger
* check here, could check dcontext equivalence, (but we
* recycle those to), probably should check threads_temp
* handle and be sure thread is still alive since the id
* won't be recycled then */
if (threads[j]->id == thread_ids_temp[i]) {
synch_array[j] = synch_array_temp[i];
break;
}
}
}
}
/* free old synch list, old thread id list */
if (num_threads_temp > 0) {
global_heap_free(thread_ids_temp, num_threads_temp * sizeof(thread_id_t)
HEAPACCT(ACCT_THREAD_MGT));
global_heap_free(synch_array_temp, num_threads_temp * sizeof(uint)
HEAPACCT(ACCT_THREAD_MGT));
num_threads_temp = 0;
}
all_synched = true;
LOG(THREAD, LOG_SYNCH, 3,
"Looping over all threads (%d threads)\n", num_threads);
#ifdef CLIENT_INTERFACE
finished_non_client_threads = true;
for (i = 0; i < num_threads; i++) {
if (threads[i]->id != my_id && synch_array[i] != SYNCH_WITH_ALL_SYNCHED &&
!IS_CLIENT_THREAD(threads[i]->dcontext)) {
finished_non_client_threads = false;
break;
}
}
#endif
/* make a copy of the thread ids (can't just keep the thread list
* since it consists of pointers to live thread_record_t structs).
* we must make the copy before synching b/c cleaning up a thread
* involves freeing its thread_record_t.
*/
thread_ids_temp = (thread_id_t *)
global_heap_alloc(num_threads * sizeof(thread_id_t)
HEAPACCT(ACCT_THREAD_MGT));
for (i = 0; i < num_threads; i++)
thread_ids_temp[i] = threads[i]->id;
num_threads_temp = num_threads;
synch_array_temp = synch_array;
for (i = 0; i < num_threads; i++) {
/* do not de-ref threads[i] after synching if it was cleaned up! */
if (synch_array[i] != SYNCH_WITH_ALL_SYNCHED && threads[i]->id != my_id) {
#ifdef CLIENT_INTERFACE
if (!finished_non_client_threads &&
IS_CLIENT_THREAD(threads[i]->dcontext)) {
all_synched = false;
continue; /* skip this thread for now till non-client are finished */
}
if (IS_CLIENT_THREAD(threads[i]->dcontext) &&
!should_suspend_client_thread(threads[i]->dcontext,
desired_synch_state)) {
/* PR 609569: do not suspend this thread.
* Avoid races between resume_all_threads() and
* dr_client_thread_set_suspendable() by storing the fact.
*
* For most of our synchall purposes we really want to prevent
* threads from acting on behalf of the application, and make
* sure we can relocate them if in the code cache. DR itself is
* thread-safe, and while a synchall-initiator will touch
* thread-private data for threads it suspends, having some
* threads it does not suspend shouldn't cause any problems so
* long as it doesn't touch their thread-private data.
*/
synch_array[i] = SYNCH_WITH_ALL_SYNCHED;
threads[i]->dcontext->client_data->left_unsuspended = true;
continue;
}
#endif
/* speed things up a tad */
if (synch_array[i] != SYNCH_WITH_ALL_NOTIFIED) {
ASSERT(synch_array[i] == SYNCH_WITH_ALL_NEW);
adjust_wait_at_safe_spot(threads[i]->dcontext, 1);
synch_array[i] = SYNCH_WITH_ALL_NOTIFIED;
}
LOG(THREAD, LOG_SYNCH, 2,
"About to try synch with thread "TIDFMT"\n", threads[i]->id);
synch_res = synch_with_thread(threads[i]->id, false, true,
THREAD_SYNCH_NONE,
desired_synch_state, flags_one);
if (synch_res == THREAD_SYNCH_RESULT_SUCCESS) {
LOG(THREAD, LOG_SYNCH, 2, "Synch succeeded!\n");
/* successful synch */
synch_array[i] = SYNCH_WITH_ALL_SYNCHED;
if (!THREAD_SYNCH_IS_CLEANED(desired_synch_state))
adjust_wait_at_safe_spot(threads[i]->dcontext, -1);
} else {
LOG(THREAD, LOG_SYNCH, 2, "Synch failed!\n");
all_synched = false;
if (synch_res == THREAD_SYNCH_RESULT_SUSPEND_FAILURE) {
if (TEST(THREAD_SYNCH_SUSPEND_FAILURE_ABORT, flags))
goto synch_with_all_abort;
} else
ASSERT(synch_res == THREAD_SYNCH_RESULT_NOT_SAFE);
}
} else {
LOG(THREAD, LOG_SYNCH, 2,
"Skipping synch with thread "TIDFMT"\n", thread_ids_temp[i]);
}
}
/* We test the exiting thread count to avoid races between exit
* process (current thread, though we could be here for detach or other
* reasons) and an exiting thread (who might no longer be on the all
* threads list) who is still using shared resources (ref case 3121) */
if (!all_synched || exiting_thread_count > expect_exiting) {
DOSTATS({
if (all_synched && exiting_thread_count > expect_exiting) {
LOG(THREAD, LOG_SYNCH, 2, "Waiting for an exiting thread %d %d %d\n",
all_synched, exiting_thread_count, expect_exiting);
STATS_INC(synch_yields_for_exiting_thread);
}
});
STATS_INC(synch_yields);
/* release lock in case some other thread waiting on it */
mutex_unlock(&thread_initexit_lock);
LOG(THREAD, LOG_SYNCH, 2, "Not all threads synched looping again\n");
/* Note - we only need call the ENTER/EXIT_DR hooks if single
* thread in dr since we are not really exiting DR here (we just
* need to give up the exclusion lock for a while to let thread we
* are trying to synch with make progress towards a safe synch
* point). */
if (INTERNAL_OPTION(single_thread_in_DR))
EXITING_DR(); /* give up DR exclusion lock */
synch_thread_yield();
if (INTERNAL_OPTION(single_thread_in_DR))
ENTERING_DR(); /* re-gain DR exclusion lock */
mutex_lock(&thread_initexit_lock);
}
}
/* case 9392: callers passing in ABORT expect a return value of failure
* to correspond w/ no suspended threads, a freed threads array, and no
* locks being held, so we go through the abort path
*/
if (!all_synched && TEST(THREAD_SYNCH_SUSPEND_FAILURE_ABORT, flags))
goto synch_with_all_abort;
synch_with_all_exit:
/* make sure we didn't exit the loop without synchronizing, FIXME : in
* release builds we assume the synchronization is failing and continue
* without it, but that is dangerous.
* It is now up to the caller to handle this, and some use
* small loop counts and abort on failure, so only a curiosity. */
ASSERT_CURIOSITY(loop_count < max_loops);
ASSERT(threads != NULL);
/* Since the set of threads can change we don't set the success field
* until we're passing back the thread list.
* We would use an tsd field directly instead of synch_array except
* for THREAD_SYNCH_*_CLEAN where tsd is freed.
*/
ASSERT(synch_array != NULL);
if (!THREAD_SYNCH_IS_CLEANED(desired_synch_state)) { /* else unsafe to access tsd */
for (i = 0; i < num_threads; i++) {
if (threads[i]->id != my_id) {
thread_synch_data_t *tsd;
ASSERT(threads[i]->dcontext != NULL);
tsd = (thread_synch_data_t *) threads[i]->dcontext->synch_field;
tsd->synch_with_success = (synch_array[i] == SYNCH_WITH_ALL_SYNCHED);
}
}
}
global_heap_free(synch_array, num_threads * sizeof(uint) HEAPACCT(ACCT_THREAD_MGT));
if (num_threads_temp > 0) {
global_heap_free(thread_ids_temp, num_threads_temp * sizeof(thread_id_t)
HEAPACCT(ACCT_THREAD_MGT));
}
/* FIXME case 9333: on all_synch failure we do not free threads array if
* synch_result is ignored. Callers are responsible for resuming threads that are
* suspended and freeing allocation for threads array
*/
if ((!all_synched && TEST(THREAD_SYNCH_SUSPEND_FAILURE_ABORT, flags))
|| THREAD_SYNCH_IS_CLEANED(desired_synch_state)) {
global_heap_free(threads, num_threads * sizeof(thread_record_t *)
HEAPACCT(ACCT_THREAD_MGT));
threads = NULL;
num_threads = 0;
}
LOG(THREAD, LOG_SYNCH, 1,
"Finished synch with all threads: result=%d\n", all_synched);
DOLOG(1, LOG_SYNCH, {
if (all_synched) {
LOG(THREAD, LOG_SYNCH, 1,
"\treturning holding initexit_lock and all_threads_synch_lock\n");
}
});
*threads_out = threads;
*num_threads_out = num_threads;
dynamo_all_threads_synched = all_synched;
/* FIXME case 9392: where on all_synch failure we do not release the locks in the
* non-abort exit path */
return all_synched;
synch_with_all_abort:
/* undo everything! */
for (i = 0; i < num_threads; i++) {
DEBUG_DECLARE(bool ok;)
if (threads[i]->id != my_id) {
if (synch_array[i] == SYNCH_WITH_ALL_SYNCHED) {
bool resume = true;
#ifdef CLIENT_SIDELINE
if (IS_CLIENT_THREAD(threads[i]->dcontext) &&
threads[i]->dcontext->client_data->left_unsuspended) {
/* PR 609569: we did not suspend this thread */
resume = false;
}
#endif
if (resume) {
DEBUG_DECLARE(ok =)
os_thread_resume(threads[i]);
ASSERT(ok);
}
/* ensure synch_with_success is set to false on exit path,
* even though locks are released and not fully valid
*/
synch_array[i] = SYNCH_WITH_ALL_NEW;
} else if (synch_array[i] == SYNCH_WITH_ALL_NOTIFIED) {
adjust_wait_at_safe_spot(threads[i]->dcontext, -1);
}
}
}
mutex_unlock(&thread_initexit_lock);
mutex_unlock(&all_threads_synch_lock);
ASSERT(!all_synched); /* ensure our OUT values will be NULL,0
for THREAD_SYNCH_SUSPEND_FAILURE_ABORT */
goto synch_with_all_exit;
}
/* Assumes that the threads were suspended with synch_with_all_threads()
* and thus even is_thread_currently_native() threads were suspended.
* Assumes that the caller will free up threads if it is dynamically allocated.
*/
void
resume_all_threads(thread_record_t **threads, const uint num_threads)
{
uint i;
thread_id_t my_tid;
bool res;
ASSERT_OWN_MUTEX(true, &all_threads_synch_lock);
ASSERT_OWN_MUTEX(true, &thread_initexit_lock);
if (threads == NULL || num_threads == 0)
return;
my_tid = get_thread_id();
for (i = 0; i < num_threads; i++) {
if (my_tid == threads[i]->id)
continue;
#ifdef CLIENT_SIDELINE
if (IS_CLIENT_THREAD(threads[i]->dcontext) &&
threads[i]->dcontext->client_data->left_unsuspended) {
/* PR 609569: we did not suspend this thread */
threads[i]->dcontext->client_data->left_unsuspended = false;
continue;
}
#endif
/* This routine assumes that each thread in the array was suspended, so
* each one has to successfully resume.
*/
res = os_thread_resume(threads[i]);
ASSERT(res);
}
}
/* Should be called to clean up after synch_with_all_threads as otherwise
* dynamo_all_threads_synched will be left as true.
* If resume is true, resumes the threads in the threads array.
* Unlocks thread_initexit_lock and all_threads_synch_lock.
* If threads != NULL, frees the threads array.
*/
void
end_synch_with_all_threads(thread_record_t **threads, uint num_threads, bool resume)
{
/* dynamo_all_threads_synched will be false if synch failed */
ASSERT_CURIOSITY(dynamo_all_threads_synched);
ASSERT(OWN_MUTEX(&all_threads_synch_lock) && OWN_MUTEX(&thread_initexit_lock));
dynamo_all_threads_synched = false;
if (resume) {
ASSERT(threads != NULL);
resume_all_threads(threads, num_threads);
}
/* if we knew whether THREAD_SYNCH_*_CLEANED was specified we could set
* synch_with_success to false, but it's unsafe otherwise
*/
mutex_unlock(&thread_initexit_lock);
mutex_unlock(&all_threads_synch_lock);
if (threads != NULL) {
global_heap_free(threads, num_threads*sizeof(thread_record_t*)
HEAPACCT(ACCT_THREAD_MGT));
}
}
/* Resets a thread's context to start interpreting anew.
* ASSUMPTION: the thread is currently suspended.
* This was moved here from fcache_reset_all_caches_proactively simply to
* get access to win32-private CONTEXT-related routines
*/
void
translate_from_synchall_to_dispatch(thread_record_t *tr, thread_synch_state_t synch_state)
{
bool res;
/* we do not have to align priv_mcontext_t */
priv_mcontext_t *mc = global_heap_alloc(sizeof(*mc) HEAPACCT(ACCT_OTHER));
bool free_cxt = true;
dcontext_t *dcontext = tr->dcontext;
app_pc pre_translation;
ASSERT(OWN_MUTEX(&all_threads_synch_lock) && OWN_MUTEX(&thread_initexit_lock));
/* FIXME: would like to assert that suspendcount is > 0 but how? */
ASSERT(thread_synch_successful(tr));
res = thread_get_mcontext(tr, mc);
ASSERT(res);
pre_translation = (app_pc) mc->pc;
LOG(GLOBAL, LOG_CACHE, 2,
"\trecreating address for "PFX"\n", mc->pc);
LOG(THREAD, LOG_CACHE, 2,
"translate_from_synchall_to_dispatch: being translated from "PFX"\n",
mc->pc);
if (get_at_syscall(dcontext)) {
/* Don't need to do anything as shared_syscall and do_syscall will not
* change due to a reset and will have any inlined ibl updated. If we
* did try to send these guys back to dispatch, have to set asynch_tag
* (as well as next_tag since translation looks only at that), restore
* TOS to asynch_target/esi (unless still at reset state), and have to
* figure out how to avoid post-syscall processing for those who never
* did pre-syscall processing (i.e., if at shared_syscall) (else will
* get wrong dcontext->sysnum, etc.)
* Not to mention that after resuming the kernel will finish the
* syscall and clobber several registers, making it hard to set a
* clean state (xref case 6113, case 5074, and notes below)!
* It's just too hard to redirect while at a syscall.
*/
LOG(GLOBAL, LOG_CACHE, 2,
"\tat syscall so not translating\n");
/* sanity check */
ASSERT(is_after_syscall_address(dcontext, pre_translation) ||
pre_translation == IF_WINDOWS_ELSE(vsyscall_after_syscall,
vsyscall_sysenter_return_pc));
} else {
res = translate_mcontext(tr, mc, true/*restore memory*/, NULL);
ASSERT(res);
if (!thread_synch_successful(tr) || mc->pc == 0) {
/* Better to risk failure on accessing a freed cache than
* to have a guaranteed crash by sending to NULL.
* FIXME: it's possible the real translation is NULL,
* but if so should be fine to leave it there since the
* current eip should also be NULL.
*/
ASSERT_NOT_REACHED();
goto translate_from_synchall_to_dispatch_exit;
}
LOG(GLOBAL, LOG_CACHE, 2,
"\ttranslation pc = "PFX"\n", mc->pc);
ASSERT(!is_dynamo_address((app_pc)mc->pc) &&
!in_fcache((app_pc)mc->pc));
/* We send all threads, regardless of whether was in DR or not, to
* re-interp from translated cxt, to avoid having to handle stale
* local state problems if we simply resumed.
* We assume no KSTATS or other state issues to deal with.
* FIXME: enter hook w/o an exit?
*/
dcontext->next_tag = (app_pc) mc->pc;
/* FIXME PR 212266: for linux if we're at an inlined syscall
* we may have problems: however, we might be able to rely on the kernel
* not clobbering any registers besides eax (which is ok: reset stub
* handles it), though presumably it's allowed to write to any
* caller-saved registers. We may need to change inlined syscalls
* to set at_syscall (see comments below as well).
*/
if (pre_translation == IF_WINDOWS_ELSE(vsyscall_after_syscall,
vsyscall_sysenter_return_pc) &&
!waiting_at_safe_spot(dcontext->thread_record, synch_state)) {
/* FIXME case 7827/PR 212266: shouldn't translate for this case, right?
* should have -ignore_syscalls set at_syscall and eliminate
* this whole block of code
*/
/* put the proper retaddr back on the stack, as we won't
* be doing the ret natively to regain control, but rather
* will interpret it
*/
/* FIXME: ensure readable and writable? */
app_pc cur_retaddr = *((app_pc *)mc->xsp);
app_pc native_retaddr;
ASSERT(cur_retaddr != NULL);
/* must be ignore_syscalls (else, at_syscall will be set) */
IF_WINDOWS(ASSERT(DYNAMO_OPTION(ignore_syscalls)));
ASSERT(get_syscall_method() == SYSCALL_METHOD_SYSENTER);
/* For DYNAMO_OPTION(sygate_sysenter) we need to restore both stack
* values and fix up esp, but we can't do it here since the kernel
* will change esp... incompatible w/ -ignore_syscalls anyway
*/
IF_WINDOWS(ASSERT_NOT_IMPLEMENTED(!DYNAMO_OPTION(sygate_sysenter)));
/* may still be at syscall from a prior reset -- don't want to grab
* locks for in_fcache so we determine via the translation
*/
ASSERT_NOT_TESTED();
native_retaddr = recreate_app_pc(dcontext, cur_retaddr, NULL);
if (native_retaddr != cur_retaddr) {
LOG(GLOBAL, LOG_CACHE, 2,
"\trestoring TOS to "PFX" from "PFX"\n", native_retaddr,
cur_retaddr);
*((app_pc *)mc->xsp) = native_retaddr;
} else {
LOG(GLOBAL, LOG_CACHE, 2,
"\tnot restoring TOS since still at previous reset state "PFX"\n",
cur_retaddr);
}
}
/* Send back to dispatch. Rather than setting up last_exit in eax here,
* we point to a special routine to save the correct eax -- in fact it's
* simply a direct exit stub. Originally this was b/c we tried to
* translate threads at system calls, and the kernel clobbers eax (and
* ecx/edx for sysenter, though preserves eip setcontext change: case
* 6113, case 5074) in finishing the system call, but now that we don't
* translate them we've kept the stub approach. It's actually faster
* for the stub itself to save eax and set the linkstub than for us to
* emulate it here, anyway.
* Note that a thread in check_wait_at_safe_spot() spins and will NOT be
* at a syscall, avoiding problems there (case 5074).
*/
mc->pc = (app_pc) get_reset_exit_stub(dcontext);
LOG(GLOBAL, LOG_CACHE, 2,
"\tsent to reset exit stub "PFX"\n", mc->pc);
/* make dispatch happy */
dcontext->whereami = WHERE_FCACHE;
#if defined(WINDOWS) && defined(CLIENT_INTERFACE)
/* i#25: we could have interrupted thread in DR, where has priv fls data
* in TEB, and fcache_return blindly copies into app fls: so swap to app
* now, just in case. DR routine can handle swapping when already app.
*/
if (INTERNAL_OPTION(private_peb) && should_swap_peb_pointer())
swap_peb_pointer(dcontext, false/*to app*/);
#endif
/* exit stub and subsequent fcache_return will save rest of state */
res = set_synched_thread_context(dcontext->thread_record, mc, NULL, 0,
synch_state _IF_X64((void *)mc)
_IF_WINDOWS(NULL));
ASSERT(res);
/* cxt is freed by set_synched_thread_context() or target thread */
free_cxt = false;
}
translate_from_synchall_to_dispatch_exit:
if (free_cxt) {
global_heap_free(mc, sizeof(*mc) HEAPACCT(ACCT_OTHER));
}
}