Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754457AbWKHIrU (ORCPT ); Wed, 8 Nov 2006 03:47:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754459AbWKHIrT (ORCPT ); Wed, 8 Nov 2006 03:47:19 -0500 Received: from relay.2ka.mipt.ru ([194.85.82.65]:34756 "EHLO 2ka.mipt.ru") by vger.kernel.org with ESMTP id S1754456AbWKHIrS (ORCPT ); Wed, 8 Nov 2006 03:47:18 -0500 Date: Wed, 8 Nov 2006 11:45:54 +0300 From: Evgeniy Polyakov To: Davide Libenzi Cc: David Miller , Ulrich Drepper , Andrew Morton , netdev , Zach Brown , Christoph Hellwig , Chase Venters , Johann Borck , Linux Kernel Mailing List , Jeff Garzik Subject: Re: [take23 3/5] kevent: poll/select() notifications. Message-ID: <20061108084554.GD2447@2ka.mipt.ru> References: <11629182482792@2ka.mipt.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.7.5 (2ka.mipt.ru [0.0.0.0]); Wed, 08 Nov 2006 11:46:17 +0300 (MSK) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1553 Lines: 41 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 > -- Evgeniy Polyakov - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/