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fix GetThreadContext call failed in mono GC for unity 5.2.x #1294

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fix GetThreadContext call failed in mono GC for unity 5.2.x #1294

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76 changes: 47 additions & 29 deletions libgc/win32_threads.c
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,9 @@ struct GC_thread_Rep {
/* !in_use ==> stack_base == 0 */
GC_bool suspended;
GC_bool should_scan;

CONTEXT saved_context; /* populated as part of GC_suspend as */
/* resume/suspend loop may be needed for call */
/* to GetThreadContext to succeed */
# ifdef CYGWIN32
void *status; /* hold exit value until join in case it's a pointer */
pthread_t pthread_id;
Expand Down Expand Up @@ -323,34 +325,53 @@ void GC_stop_world()
while (SuspendThread(thread_table[i].handle) == (DWORD)-1)
Sleep(10);
# else
/* Apparently the Windows 95 GetOpenFileName call creates */
/* a thread that does not properly get cleaned up, and */
/* SuspendThread on its descriptor may provoke a crash. */
/* This reduces the probability of that event, though it still */
/* appears there's a race here. */
DWORD exitCode;
if (GetExitCodeThread(thread_table[i].handle,&exitCode) &&
exitCode != STILL_ACTIVE) {
thread_table[i].stack_base = 0; /* prevent stack from being pushed */
# ifndef CYGWIN32
/* this breaks pthread_join on Cygwin, which is guaranteed to */
/* only see user pthreads */
thread_table[i].in_use = FALSE;
CloseHandle(thread_table[i].handle);
# endif
continue;
}
if (SuspendThread(thread_table[i].handle) == (DWORD)-1) {
thread_table[i].stack_base = 0; /* prevent stack from being pushed */

int iterations = 0;
while (TRUE)
{
/* Apparently the Windows 95 GetOpenFileName call creates */
/* a thread that does not properly get cleaned up, and */
/* SuspendThread on its descriptor may provoke a crash. */
/* This reduces the probability of that event, though it still */
/* appears there's a race here. */
DWORD exitCode;
volatile struct GC_thread_Rep* t;
DWORD res;
if (GetExitCodeThread(thread_table[i].handle,&exitCode) &&
exitCode != STILL_ACTIVE) {
thread_table[i].stack_base = 0; /* prevent stack from being pushed */
# ifndef CYGWIN32
/* this breaks pthread_join on Cygwin, which is guaranteed to */
/* only see user pthreads */
thread_table[i].in_use = FALSE;
CloseHandle(thread_table[i].handle);
/* this breaks pthread_join on Cygwin, which is guaranteed to */
/* only see user pthreads */
thread_table[i].in_use = FALSE;
CloseHandle(thread_table[i].handle);
# endif
continue;
}

t = &thread_table[i];

do {
res = SuspendThread (t->handle);
} while (res == (DWORD)-1);

t->saved_context.ContextFlags = CONTEXT_INTEGER | CONTEXT_CONTROL;
if (GetThreadContext (t->handle, &t->saved_context)) {
t->suspended = (unsigned char)TRUE;
break; /* success case break out of loop */
}

/* resume thread and try to suspend in better location */
if (ResumeThread (t->handle) == (DWORD)-1)
ABORT ("ResumeThread failed");

/* after a million tries something must be wrong */
if (iterations++ == 1000 * 1000)
ABORT ("SuspendThread loop failed");

}
# endif
thread_table[i].suspended = TRUE;
thread_table[i].suspended = TRUE;
}
# ifndef CYGWIN32
LeaveCriticalSection(&GC_write_cs);
Expand Down Expand Up @@ -437,10 +458,7 @@ void GC_push_all_stacks()
continue;
}
else {
CONTEXT context;
context.ContextFlags = CONTEXT_INTEGER|CONTEXT_CONTROL;
if (!GetThreadContext(thread_table[i].handle, &context))
ABORT("GetThreadContext failed");
CONTEXT context = thread_table[i].saved_context;

/* Push all registers that might point into the heap. Frame */
/* pointer registers are included in case client code was */
Expand Down