Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752659AbaF0ESj (ORCPT ); Fri, 27 Jun 2014 00:18:39 -0400 Received: from mail.linux-iscsi.org ([67.23.28.174]:56694 "EHLO linux-iscsi.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751120AbaF0ESh (ORCPT ); Fri, 27 Jun 2014 00:18:37 -0400 Message-ID: <1403842714.22367.8.camel@haakon3.risingtidesystems.com> Subject: Re: [PATCH] target: fix deadlock on unload From: "Nicholas A. Bellinger" To: Mikulas Patocka Cc: linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 26 Jun 2014 21:18:34 -0700 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mikulas, On Mon, 2014-06-23 at 13:42 -0400, Mikulas Patocka wrote: > target: fix deadlock on unload > > On uniprocessor preemptible kernel, target core deadlocks on unload. The > following events happen: > * iscsit_del_np is called > * it calls send_sig(SIGINT, np->np_thread, 1); > * the scheduler switches to the np_thread > * the np_thread is woken up, it sees that kthread_should_stop() returns > false, so it doesn't terminate > * the np_thread clears signals with flush_signals(current); and goes back > to sleep in iscsit_accept_np > * the scheduler switches back to iscsit_del_np > * iscsit_del_np calls kthread_stop(np->np_thread); > * the np_thread is waiting in iscsit_accept_np and it doesn't respond to > kthread_stop > > The deadlock could be resolved if the administrator sends SIGINT signal to > the np_thread with killall -INT iscsi_np > > The reproducible deadlock was introduced in commit > db6077fd0b7dd41dc6ff18329cec979379071f87, but the thread-stopping code was > racy even before. > > This patch fixes the problem. Using kthread_should_stop to stop the > np_thread is unreliable, so we test np_thread_state instead. If > np_thread_state equals ISCSI_NP_THREAD_SHUTDOWN, the thread exits. > > Signed-off-by: Mikulas Patocka > Cc: stable@vger.kernel.org > Apologies for the delayed response.. Applied to target-pending/master and including in the next -rc3 PULL request. Also FYI, I've added '3.12+' to the stable tag to match how far back commit db6077fd0 has been included in stable. Thanks, --nab -- 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/