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fix data race choosing next key slot in pthread_key_create 

commit 84d061d5a3 wrongly moved the
access to the global next_key outside of the scope of the lock. the
error manifested as spurious failure to find an available key slot
under concurrent calls to pthread_key_create, since the stopping
condition could be met after only a small number of slots were
examined.
This commit is contained in:
Rich Felker 2019-03-21 13:58:12 -04:00
parent 8f12c4e110
commit 59f88d7662
1 changed files with 1 additions and 1 deletions
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2
src/thread/pthread_key_create.c
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@ -22,7 +22,6 @@ weak_alias(dummy_0, __tl_unlock);
int __pthread_key_create(pthread_key_t *k, void (*dtor)(void *)) int __pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
{ {
pthread_key_t j = next_key;
pthread_t self = __pthread_self(); pthread_t self = __pthread_self();
/* This can only happen in the main thread before /* This can only happen in the main thread before
@ -33,6 +32,7 @@ int __pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
if (!dtor) dtor = nodtor; if (!dtor) dtor = nodtor;
__pthread_rwlock_wrlock(&key_lock); __pthread_rwlock_wrlock(&key_lock);
pthread_key_t j = next_key;
do { do {
if (!keys[j]) { if (!keys[j]) {
keys[next_key = *k = j] = dtor; keys[next_key = *k = j] = dtor;