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fix serious bug in pthread_join 

on spurious wakeups/returns from __timedwait, pthread_join would
"succeed" and unmap the thread's stack while it was still running. at
best this would lead to SIGSEGV when the thread resumed execution, but
in the worst case, the thread would later resume executing on top of
another new thread's stack mapped at the same address.

spent about 4 hours tracking this bug down, chasing rare
difficult-to-reproduce stack corruption in a stress test program.
still no idea *what* caused the spurious wakeups; i suspect it's a
kernel bug.
This commit is contained in:
Rich Felker 2011-09-11 12:35:41 -04:00
parent eb351a9e63
commit 8fe5fa56ee
1 changed files with 2 additions and 2 deletions
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4
src/thread/pthread_join.c
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@ -6,8 +6,8 @@ static void dummy(void *p)
int pthread_join(pthread_t t, void **res) int pthread_join(pthread_t t, void **res)
{ {
int tmp = t->tid; int tmp;
if (tmp) __timedwait(&t->tid, tmp, 0, 0, dummy, 0, 0); while ((tmp = t->tid)) __timedwait(&t->tid, tmp, 0, 0, dummy, 0, 0);
if (res) *res = t->result; if (res) *res = t->result;
if (t->map_base) munmap(t->map_base, t->map_size); if (t->map_base) munmap(t->map_base, t->map_size);
return 0; return 0;