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fix data race between new pthread_key_delete and dtor execution

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access to clear the entry in each thread's tsd array for the key being
deleted was not synchronized with __pthread_tsd_run_dtors. I probably
made this mistake from a mistaken belief that the thread list lock was
held during the latter, which of course is not possible since it
executes application code in a still-live-thread context.

while we're at it, expand the interval during which signals are
blocked to cover taking the write lock on key_lock, so that a signal
at an inopportune time doesn't block forward progress of readers.
This commit is contained in:
Rich Felker 2019-02-17 21:46:14 -05:00
parent 639bcf251e
commit 805288929f
1 changed files with 4 additions and 2 deletions
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6
src/thread/pthread_key_create.c
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@ -51,15 +51,17 @@ int __pthread_key_delete(pthread_key_t k)
pthread_t self = __pthread_self(), td=self;
__block_app_sigs(&set);
__pthread_rwlock_wrlock(&key_lock);
__tl_lock();
do td->tsd[k] = 0;
while ((td=td->next)!=self);
__tl_unlock();
__restore_sigs(&set);
__pthread_rwlock_wrlock(&key_lock);
keys[k] = 0;
__pthread_rwlock_unlock(&key_lock);
__restore_sigs(&set);
return 0;
}