Messages in this thread | | | Date | Mon, 7 May 2007 15:35:38 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [PATCH] rfc: threaded epoll_wait thundering herd |
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On Mon, 7 May 2007, Ulrich Drepper wrote:
> On 5/7/07, Davi Arnaut <davi@haxent.com.br> wrote: > > See Linus's message on this same thread. > > No. I'm talking about the userlevel side, not kernel side. > > If a thread is canceled *after* it returns from the syscall but before > it reports the event to the call (i.e., while still in the syscall > wrapper, thread cancellation rules require a check there) the event is > lost.
read(2) is a cancellation point too. So if the fine userspace code issues a random pthread_cancel() to a thread handling that, data is lost together with the session that thread was handling. Hmm, I wonder how the world could have functioned so far. Bottom line is, if you really want to throw random cancels to your worker threads, you better wrap them into pthread_cleanup_push(). Because otherwise, no matter where your cancel hits, you end up with a broken system.
- Davide
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