* Lai Jiangshan ([email protected]) wrote:
> thread1: thread2
> thr_defer()
> pthread_testcancel();
> stop_defer_thread() .
> pthread_cancel(tid_defer); .
> wake_up_defer(); .
> wait_defer();
> pthread_join(tid_defer)
>
> thread2 missing respond to the cancellation request from thread1
> and wait callback forever.
>
> thread1 wait thread2 forver by pthread_join():
>
> Signed-off-by: Lai Jiangshan <[email protected]>
> ---
> urcu-defer-impl.h | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/urcu-defer-impl.h b/urcu-defer-impl.h
> index d1ab046..6339747 100644
> --- a/urcu-defer-impl.h
> +++ b/urcu-defer-impl.h
> @@ -187,6 +187,7 @@ static void wait_defer(void)
> {
> uatomic_dec(&defer_thread_futex);
> cmm_smp_mb(); /* Write futex before read queue */
> + pthread_testcancel();
> if (rcu_defer_num_callbacks()) {
> cmm_smp_mb(); /* Read queue before write futex */
> /* Callbacks are queued, don't wait. */
> @@ -359,7 +360,6 @@ void _defer_rcu(void (*fct)(void *p), void *p)
> void *thr_defer(void *args)
> {
> for (;;) {
> - pthread_testcancel();
> /*
> * "Be green". Don't wake up the CPU if there is no RCU work
> * to perform whatsoever. Aims at saving laptop battery life by
Shouldn't we just modify futex_noasync and futex_async to add a
pthread_testcancel there instead ? We should then document, in futex.h,
that our futex implementations are pthread cancellation points.
> @@ -387,6 +387,7 @@ static void start_defer_thread(void)
> {
> int ret;
>
> + uatomic_set(&defer_thread_futex, 0);
this would be to handle a start/stop/start sequence, right ? If we put
the testcancel within the region where the defer thread can have the
futex value set to non-zero, I guess setting it back to zero upon
restart will be required. Instead of setting it back to 0 in the
"start", we could theoretically let stop_defer_thread() do it, because
the first "start" will already have its value set to 0. We have to
notice that this whole rcu_defer scheme does not deal well with fork()
that are not followed by exec() though. We should probably just
document this and not care about it: call_rcu() is a superset of
defer_rcu anyway, and we should encourage use of call_rcu.
Thanks,
Mathieu
> ret = pthread_create(&tid_defer, NULL, thr_defer, NULL);
> assert(!ret);
> }
> --
> 1.7.4.4
>
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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