From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754981AbaDOShg (ORCPT ); Tue, 15 Apr 2014 14:37:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64635 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754567AbaDOSha (ORCPT ); Tue, 15 Apr 2014 14:37:30 -0400 Date: Tue, 15 Apr 2014 20:36:59 +0200 From: Oleg Nesterov To: Andrew Morton , Peter Zijlstra Cc: Al Viro , David Woodhouse , Frederic Weisbecker , Geert Uytterhoeven , Ingo Molnar , Mathieu Desnoyers , Richard Weinberger , Steven Rostedt , Tejun Heo , linux-kernel@vger.kernel.org Subject: [PATCH RESEND2 07/11] signals: jffs2: fix the wrong usage of disallow_signal() Message-ID: <20140415183659.GA13419@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140415183625.GA13371@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org jffs2_garbage_collect_thread() does disallow_signal(SIGHUP) around jffs2_garbage_collect_pass() and the comment says "We don't want SIGHUP to interrupt us". But disallow_signal() can't ensure that jffs2_garbage_collect_pass() won't be interrupted by SIGHUP, the problem is that SIGHUP can be already pending when disallow_signal() is called, and in this case any interruptible sleep won't block. Note: this is in fact because disallow_signal() is buggy and should be fixed, see the next changes. But there is another reason why disallow_signal() is wrong: SIG_IGN set by disallow_signal() silently discards any SIGHUP which can be sent before the next allow_signal(SIGHUP). Change this code to use sigprocmask(SIG_UNBLOCK/SIG_BLOCK, SIGHUP). This even matches the old (and wrong) semantics allow/disallow had when this logic was written. Signed-off-by: Oleg Nesterov --- fs/jffs2/background.c | 12 +++++++----- 1 files changed, 7 insertions(+), 5 deletions(-) diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c index 2b60ce1..bb9cebc 100644 --- a/fs/jffs2/background.c +++ b/fs/jffs2/background.c @@ -75,10 +75,13 @@ void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c) static int jffs2_garbage_collect_thread(void *_c) { struct jffs2_sb_info *c = _c; + sigset_t hupmask; + siginitset(&hupmask, sigmask(SIGHUP)); allow_signal(SIGKILL); allow_signal(SIGSTOP); allow_signal(SIGCONT); + allow_signal(SIGHUP); c->gc_task = current; complete(&c->gc_thread_start); @@ -87,7 +90,7 @@ static int jffs2_garbage_collect_thread(void *_c) set_freezable(); for (;;) { - allow_signal(SIGHUP); + sigprocmask(SIG_UNBLOCK, &hupmask, NULL); again: spin_lock(&c->erase_completion_lock); if (!jffs2_thread_should_wake(c)) { @@ -95,10 +98,9 @@ static int jffs2_garbage_collect_thread(void *_c) spin_unlock(&c->erase_completion_lock); jffs2_dbg(1, "%s(): sleeping...\n", __func__); schedule(); - } else + } else { spin_unlock(&c->erase_completion_lock); - - + } /* Problem - immediately after bootup, the GCD spends a lot * of time in places like jffs2_kill_fragtree(); so much so * that userspace processes (like gdm and X) are starved @@ -150,7 +152,7 @@ static int jffs2_garbage_collect_thread(void *_c) } } /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */ - disallow_signal(SIGHUP); + sigprocmask(SIG_BLOCK, &hupmask, NULL); jffs2_dbg(1, "%s(): pass\n", __func__); if (jffs2_garbage_collect_pass(c) == -ENOSPC) { -- 1.5.5.1