From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: [merged] signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch removed from -mm tree Date: Mon, 09 Jun 2014 12:34:07 -0700 Message-ID: <53960c2f.teWs1VwNGwJYOMKm%akpm@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:54053 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750904AbaFITeI (ORCPT ); Mon, 9 Jun 2014 15:34:08 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org, viro@ZenIV.linux.org.uk, tj@kernel.org, rostedt@goodmis.org, richard@nod.at, peterz@infradead.org, mingo@kernel.org, mathieu.desnoyers@efficios.com, geert@linux-m68k.org, fweisbec@gmail.com, dwmw2@infradead.org, oleg@redhat.com Subject: [merged] signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch removed from -mm tree To: oleg@redhat.com,dwmw2@infradead.org,fweisbec@gmail.com,geert@linux-m68k.org,mathieu.desnoyers@efficios.com,mingo@kernel.org,peterz@infradead.org,richard@nod.at,rostedt@goodmis.org,tj@kernel.org,viro@ZenIV.linux.org.uk,mm-commits@vger.kernel.org From: akpm@linux-foundation.org Date: Mon, 09 Jun 2014 12:34:07 -0700 The patch titled Subject: signals: jffs2: fix the wrong usage of disallow_signal() has been removed from the -mm tree. Its filename was signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Oleg Nesterov Subject: signals: jffs2: fix the wrong usage of disallow_signal() 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 Cc: Peter Zijlstra Cc: Al Viro Cc: David Woodhouse Cc: Frederic Weisbecker Cc: Geert Uytterhoeven Cc: Ingo Molnar Cc: Mathieu Desnoyers Cc: Richard Weinberger Cc: Steven Rostedt Cc: Tejun Heo Signed-off-by: Andrew Morton --- fs/jffs2/background.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff -puN fs/jffs2/background.c~signals-jffs2-fix-the-wrong-usage-of-disallow_signal fs/jffs2/background.c --- a/fs/jffs2/background.c~signals-jffs2-fix-the-wrong-usage-of-disallow_signal +++ a/fs/jffs2/background.c @@ -75,10 +75,13 @@ void jffs2_stop_garbage_collect_thread(s 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( 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( 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( } } /* 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) { _ Patches currently in -mm which might be from oleg@redhat.com are origin.patch cpu-hotplug-smp-flush-any-pending-ipi-callbacks-before-cpu-offline.patch linux-next.patch kernel-watchdogc-print-traces-for-all-cpus-on-lockup-detection.patch kernel-watchdogc-print-traces-for-all-cpus-on-lockup-detection-fix.patch nmi-provide-the-option-to-issue-an-nmi-back-trace-to-every-cpu-but-current.patch nmi-provide-the-option-to-issue-an-nmi-back-trace-to-every-cpu-but-current-fix.patch