From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933173AbeAXKn7 (ORCPT ); Wed, 24 Jan 2018 05:43:59 -0500 Received: from terminus.zytor.com ([65.50.211.136]:56349 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932966AbeAXKn5 (ORCPT ); Wed, 24 Jan 2018 05:43:57 -0500 Date: Wed, 24 Jan 2018 02:37:55 -0800 From: tip-bot for Peter Zijlstra Message-ID: Cc: peterz@infradead.org, hpa@zytor.com, geert@linux-m68k.org, tglx@linutronix.de, akpm@linux-foundation.org, mingo@kernel.org, paulmck@us.ibm.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, davej@codemonkey.org.uk Reply-To: peterz@infradead.org, hpa@zytor.com, geert@linux-m68k.org, tglx@linutronix.de, akpm@linux-foundation.org, mingo@kernel.org, paulmck@us.ibm.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, davej@codemonkey.org.uk In-Reply-To: <20180122103947.GD2228@hirez.programming.kicks-ass.net> References: <20180122103947.GD2228@hirez.programming.kicks-ass.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/urgent] futex: Fix OWNER_DEAD fixup Git-Commit-ID: a97cb0e7b3f4c6297fd857055ae8e895f402f501 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: a97cb0e7b3f4c6297fd857055ae8e895f402f501 Gitweb: https://git.kernel.org/tip/a97cb0e7b3f4c6297fd857055ae8e895f402f501 Author: Peter Zijlstra AuthorDate: Mon, 22 Jan 2018 11:39:47 +0100 Committer: Ingo Molnar CommitDate: Wed, 24 Jan 2018 09:58:18 +0100 futex: Fix OWNER_DEAD fixup Both Geert and DaveJ reported that the recent futex commit: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex") introduced a problem with setting OWNER_DEAD. We set the bit on an uninitialized variable and then entirely optimize it away as a dead-store. Move the setting of the bit to where it is more useful. Reported-by: Geert Uytterhoeven Reported-by: Dave Jones Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex") Link: http://lkml.kernel.org/r/20180122103947.GD2228@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/futex.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 8c5424d..7f719d1 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2311,9 +2311,6 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock); oldowner = pi_state->owner; - /* Owner died? */ - if (!pi_state->owner) - newtid |= FUTEX_OWNER_DIED; /* * We are here because either: @@ -2374,6 +2371,9 @@ retry: } newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; + /* Owner died? */ + if (!pi_state->owner) + newtid |= FUTEX_OWNER_DIED; if (get_futex_value_locked(&uval, uaddr)) goto handle_fault;