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nptl: wait for pending setxid request also in detached thread (bug 25942)

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There is a race between __nptl_setxid and exiting detached thread, which
causes a deadlock on stack_cache_lock.  The deadlock happens in this
state:

T1: setgroups -> __nptl_setxid (holding stack_cache_lock, waiting on cmdp->cntr == 0)
T2 (detached, exiting): start_thread -> __deallocate_stack (waiting on stack_cache_lock)
more threads waiting on stack_cache_lock in pthread_create

For non-detached threads, start_thread waits for its own setxid handler to
finish before exiting.  Do this for detached threads as well.
This commit is contained in:
Andreas Schwab 2020-05-07 15:50:09 +02:00
parent 16536e98e3
commit 4cab20fa49
1 changed files with 6 additions and 5 deletions
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11
nptl/pthread_create.c
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@ -552,11 +552,7 @@ START_THREAD_DEFN
advise_stack_range (pd->stackblock, pd->stackblock_size, (uintptr_t) pd,
pd->guardsize);
/* If the thread is detached free the TCB. */
if (IS_DETACHED (pd))
/* Free the TCB. */
__free_tcb (pd);
else if (__glibc_unlikely (pd->cancelhandling & SETXID_BITMASK))
if (__glibc_unlikely (pd->cancelhandling & SETXID_BITMASK))
{
/* Some other thread might call any of the setXid functions and expect
us to reply. In this case wait until we did that. */
@ -572,6 +568,11 @@ START_THREAD_DEFN
pd->setxid_futex = 0;
}
/* If the thread is detached free the TCB. */
if (IS_DETACHED (pd))
/* Free the TCB. */
__free_tcb (pd);
/* We cannot call '_exit' here. '_exit' will terminate the process.
The 'exit' implementation in the kernel will signal when the