Messages in this thread | | | Date | Wed, 8 Nov 2006 11:45:54 +0300 | From | Evgeniy Polyakov <> | Subject | Re: [take23 3/5] kevent: poll/select() notifications. |
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On Tue, Nov 07, 2006 at 02:53:33PM -0800, Davide Libenzi (davidel@xmailserver.org) wrote: > On Tue, 7 Nov 2006, Evgeniy Polyakov wrote: > > > +static int kevent_poll_wait_callback(wait_queue_t *wait, > > + unsigned mode, int sync, void *key) > > +{ > > + struct kevent_poll_wait_container *cont = > > + container_of(wait, struct kevent_poll_wait_container, wait); > > + struct kevent *k = cont->k; > > + struct file *file = k->st->origin; > > + u32 revents; > > + > > + revents = file->f_op->poll(file, NULL); > > + > > + kevent_storage_ready(k->st, NULL, revents); > > + > > + return 0; > > +} > > Are you sure you can safely call file->f_op->poll() from inside a callback > based wakeup? The low level driver may be calling the wakeup with one of > its locks held, and during the file->f_op->poll may be trying to acquire > the same lock. I remember there was a discussion about this, and assuming > the above not true, made epoll code more complex (and slower, since an > extra O(R) loop was needed to fetch events).
Indeed, I have not paid too much attention to poll/select notifications in kevent actually. As far as I recall it should be called on behalf of process doing kevent_get_event(). I will check and fix if that is not correct. Thanks Davide.
> - Davide >
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