Messages in this thread | | | Date | Thu, 22 May 2008 15:12:11 +0400 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/3] signals: sigqueue_free: don't free sigqueue if it is queued |
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On 05/21, Roland McGrath wrote: > > -void flush_sigqueue(struct sigpending *queue) > +static void __flush_sigqueue(struct sigpending *queue, int timers) > { > struct sigqueue *q; > > sigemptyset(&queue->signal); > while (!list_empty(&queue->list)) { > q = list_entry(queue->list.next, struct sigqueue , list); > + if (timers && q->info.si_code != SI_TIMER) > + continue; > list_del_init(&q->list); > __sigqueue_free(q); > } > }
This is not enough. Again, we remove and free sigqueue but don't discard the pending signal. (and we must take into account other rt signals with the same si_signo if we want to discard the signal).
Oh, this problem is unexpectedly nasty. It is trivial and minor, we can solve it in may ways, but personally I can't find a simple/clean way.
Let's look at my first attempt,
http://marc.info/?l=linux-kernel&m=120888210417700
the patch was "almost" correct. We can add the "bool cancel" parameter to sigqueue_free(), true when called from exec (or exit_itimers). In that case SIGQUEUE_SHARED_PENDING is enough: the pending signal was either sent to current, or it is group wide. Not nice too of course, but afaics a bit simpler. Actually, the patch exists: http://marc.info/?l=linux-kernel&m=120888210417698
What do you think?
(instead of SIGQUEUE_SHARED_PENDING, we can encode "struct sigpending *" in q->flags, but this is really awful and I agree with Linus on the EINTR/etc issues).
I'll try to think more on Weekend.
Oleg.
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