pthread_cond_signal is not needed in case that no thread is blocked on the cond var.
Take a inter-thread shared queue as an example, which maintains a counter couting blocked threads
1 void pop(void **data) { 2 pthread_mutex_lock(&mtx); 3 while (queue_size == 0) { 4 count++; 5 pthread_cond_wait(&cv, &mtx); 6 count--; 7 } 8 // ... pop the front item into data 9 pthread_mutex_lock(&mtx); 10 } 11 12 void push(void *data) { 13 pthread_mutex_lock(&mtx); 14 // ... push data into queue 15 if (count > 0) { 16 pthread_cond_signal(&cv); 17 } 18 pthread_mutex_lock(&mtx); 19 }
【perf】reduce pthread_cond_signal via wait counter
原文：https://www.cnblogs.com/albumcover/p/9339059.html