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Fix mutex locking in _pkcs11h_threading_cond{Init,Wait} functions. #65

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Fix mutex locking in _pkcs11h_threading_cond{Init,Wait} functions. #65

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17 changes: 15 additions & 2 deletions lib/pkcs11h-threading.c
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Original file line number Diff line number Diff line change
Expand Up @@ -388,8 +388,7 @@ _pkcs11h_threading_condInit (
if (
(
pthread_mutex_init (&cond->mut, NULL) ||
pthread_cond_init (&cond->cond, NULL) ||
pthread_mutex_lock (&cond->mut)
pthread_cond_init (&cond->cond, NULL)
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)
) {
rv = CKR_FUNCTION_FAILED;
Expand Down Expand Up @@ -423,7 +422,13 @@ _pkcs11h_threading_condWait (
goto cleanup;
}
#else
int unlock_mutex = 0;
if (milli == PKCS11H_COND_INFINITE) {
if (pthread_mutex_lock (&cond->mut)) {
rv = CKR_FUNCTION_FAILED;
goto cleanup;
}
unlock_mutex = 1;
if (pthread_cond_wait (&cond->cond, &cond->mut) ) {
rv = CKR_FUNCTION_FAILED;
goto cleanup;
Expand All @@ -441,6 +446,11 @@ _pkcs11h_threading_condWait (
timeout.tv_sec = now.tv_sec + milli/1000;
timeout.tv_nsec = now.tv_usec*1000 + milli%1000;

if (pthread_mutex_trylock (&cond->mut)) {
rv = CKR_FUNCTION_FAILED;
goto cleanup;
}
unlock_mutex = 1;
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this should wait not fail if other holds the lock, can it be done?

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We could spin in a loop calling pthread_mutex_trylock until times passes out. But this is basically a spinlock.
Not sure if this is a good idea.

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as far as I remember this was my initial use of cond as mutex cannot wait... yes, spin loop is bad, there must be a different solution, otherwise the pthread_cond_timedwait has little sense.

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If the mutex is only used for waiting on the condition variable, the amount of time it is locked should be really short. Maybe spinlock here is actually OK.

Anyways, this change doesn't make the code any worse than it was.

if (pthread_cond_timedwait (&cond->cond, &cond->mut, &timeout)) {
rv = CKR_FUNCTION_FAILED;
goto cleanup;
Expand All @@ -449,6 +459,9 @@ _pkcs11h_threading_condWait (
#endif
rv = CKR_OK;
cleanup:
if (unlock_mutex) {
pthread_mutex_unlock (&cond->mut);
}
return rv;
}

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