On Wed, Oct 14, 2020 at 08:39:51AM -0700, Ian Rogers wrote: > On Wed, Oct 14, 2020 at 4:45 AM Jiri Olsa <jo...@redhat.com> wrote: > > > > On Mon, Oct 12, 2020 at 09:16:11AM -0700, Ian Rogers wrote: > > > > SNIP > > > > > @@ -483,6 +484,18 @@ static void init_global_mutex(pthread_mutex_t *mutex) > > > pthread_mutex_init(mutex, &attr); > > > } > > > > > > +/* > > > + * Return a process-shared (global) condition variable: > > > + */ > > > +static void init_global_cond(pthread_cond_t *cond) > > > +{ > > > + pthread_condattr_t attr; > > > + > > > + pthread_condattr_init(&attr); > > > + pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED); > > > + pthread_cond_init(cond, &attr); > > > +} > > > + > > > static int parse_cpu_list(const char *arg) > > > { > > > p0.cpu_list_str = strdup(arg); > > > @@ -1136,15 +1149,18 @@ static void *worker_thread(void *__tdata) > > > if (g->p.serialize_startup) { > > > pthread_mutex_lock(&g->startup_mutex); > > > g->nr_tasks_started++; > > > + /* The last thread wakes the main process. */ > > > + if (g->nr_tasks_started == g->p.nr_tasks) > > > + pthread_cond_signal(&g->startup_cond); > > > > should you remove the condition? it's not necessary > > and making this racy, no? > > > > just single pthread_cond_signal should be enough, > > because the wait code is checking the number of tasks > > The pthread_mutex_lock avoids any race on g->nr_tasks_started and > g->p.nr_tasks is set up in init() along with all the global state. I > don't think there's any race on g->nr_tasks_started and doing a signal > for every thread starting will just cause unnecessary wake-ups for the > main thread. I think it is better to keep it. I added loops on all the > pthread_cond_waits so the code is robust against spurious wake ups.
ah, I missed that mutex call Acked-by: Jiri Olsa <jo...@redhat.com> thanks, jirka