Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422974AbWLURiH (ORCPT ); Thu, 21 Dec 2006 12:38:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422993AbWLURiH (ORCPT ); Thu, 21 Dec 2006 12:38:07 -0500 Received: from mx1.redhat.com ([66.187.233.31]:60591 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422974AbWLURiG (ORCPT ); Thu, 21 Dec 2006 12:38:06 -0500 To: "Chen, Kenneth W" Cc: "'Andrew Morton'" , , "'Trond Myklebust'" , "'xb'" , "'Zach Brown'" , , "Paul E. McKenney" Subject: Re: [patch] aio: fix buggy put_ioctx call in aio_complete X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? References: <000601c72521$ab1d4880$fe80030a@amr.corp.intel.com> From: jmoyer@redhat.com Date: Thu, 21 Dec 2006 12:34:52 -0500 In-Reply-To: <000601c72521$ab1d4880$fe80030a@amr.corp.intel.com> (Kenneth W. Chen's message of "Thu, 21 Dec 2006 09:01:28 -0800") Message-ID: User-Agent: Gnus/5.1007 (Gnus v5.10.7) XEmacs/21.5-b27 (linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2163 Lines: 42 ==> Regarding RE: [patch] aio: fix buggy put_ioctx call in aio_complete; "Chen, Kenneth W" adds: kenneth.w.chen> jmoyer@redhat.com wrote on Thursday, December 21, 2006 8:56 kenneth.w.chen> AM I think I'm going to abandon this whole synchronize kenneth.w.chen> thing and going to put the wake up call inside ioctx_lock kenneth.w.chen> spin lock along with the other patch you mentioned above in kenneth.w.chen> the waiter path. On top of that, I have another patch kenneth.w.chen> attempts to perform wake-up only when the waiter can truly kenneth.w.chen> proceed in aio_read_evt so dribbling I/O completion doesn't kenneth.w.chen> inefficiently waking up waiter too frequently and only to kenneth.w.chen> have waiter put back to sleep again. I will dig that up and kenneth.w.chen> experiment. >> In the mean time, can't we simply take the context lock in >> wait_for_all_aios? Unless I missed something, I think that will address >> the reference count problem. kenneth.w.chen> Take ioctx_lock is one part, the other part is to move kenneth.w.chen> spin_unlock_irqrestore(&ctx->ctx_lock, flags); kenneth.w.chen> in aio_complete all the way down to the end of the kenneth.w.chen> function, after wakeup and put_ioctx. But then the ref kenneth.w.chen> counting on ioctx in aio_complete path is Meaningless, kenneth.w.chen> which is the thing I'm trying to remove. OK, right. But are we simply papering over the real problem? Earlier in this thread, you stated: > flush_workqueue() is not allowed to be called in the softirq context. > However, aio_complete() called from I/O interrupt can potentially call > put_ioctx with last ref count on ioctx and trigger a bug warning. It > is simply incorrect to perform ioctx freeing from aio_complete. But how do we end up with the last reference to the ioctx in the aio completion path? That's a question I haven't seen answered. -Jeff - 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/