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Possible patch for POSIX conditional wait issue #356

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merged 1 commit into from
Oct 2, 2023
Merged

Possible patch for POSIX conditional wait issue #356

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14 changes: 8 additions & 6 deletions src/mqtt_client.c
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Original file line number Diff line number Diff line change
Expand Up @@ -81,29 +81,31 @@ static int MqttClient_Publish_ReadPayload(MqttClient* client,
}
#elif defined(WOLFMQTT_POSIX_SEMAPHORES)
/* Posix style semaphore */
int wm_SemInit(wm_Sem *s){
int wm_SemInit(wm_Sem *s) {
s->lockCount = 0;
pthread_mutex_init(&s->mutex, NULL);
pthread_cond_init(&s->cond, NULL);
return 0;
}
int wm_SemFree(wm_Sem *s){
int wm_SemFree(wm_Sem *s) {
pthread_mutex_destroy(&s->mutex);
pthread_cond_destroy(&s->cond);
return 0;
}
int wm_SemLock(wm_Sem *s){
int wm_SemLock(wm_Sem *s) {
pthread_mutex_lock(&s->mutex);
while (s->lockCount > 0)
pthread_cond_wait(&s->cond, &s->mutex);
s->lockCount++;
pthread_mutex_unlock(&s->mutex);
return 0;
}
int wm_SemUnlock(wm_Sem *s){
int wm_SemUnlock(wm_Sem *s) {
pthread_mutex_lock(&s->mutex);
s->lockCount--;
pthread_cond_signal(&s->cond);
if (s->lockCount > 0) {
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Should the else case here return an error code?

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We don't handle the wm_SemUnlock return code anywhere in wolfMQTT. However I will run some tests and see if this case ever occurs. I suspect it might and that's okay and should not be considered an error.

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Our test cases aren't triggering it, however I think with the complicated locks in the state machine for lockRecv with the right abort this might be able to occur. Ignoring it is safe "in my opinion".

s->lockCount--;
pthread_cond_signal(&s->cond);
}
pthread_mutex_unlock(&s->mutex);
return 0;
}
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