From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754070AbdK1SmV (ORCPT ); Tue, 28 Nov 2017 13:42:21 -0500 Received: from foss.arm.com ([217.140.101.70]:58318 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751676AbdK1SmS (ORCPT ); Tue, 28 Nov 2017 13:42:18 -0500 From: Will Deacon To: linux-kernel@vger.kernel.org Cc: sebott@linux.vnet.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, peterz@infradead.org, mingo@kernel.org, Will Deacon Subject: [PATCH 1/2] locking/core: Fix deadlock during boot on systems with GENERIC_LOCKBREAK Date: Tue, 28 Nov 2017 18:42:18 +0000 Message-Id: <1511894539-7988-2-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1511894539-7988-1-git-send-email-will.deacon@arm.com> References: <1511894539-7988-1-git-send-email-will.deacon@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit a8a217c22116 ("locking/core: Remove {read,spin,write}_can_lock()") removed the definition of raw_spin_can_lock, causing the GENERIC_LOCKBREAK spin_lock routines to poll the break_lock field when waiting on a lock. This has been reported to cause a deadlock during boot on s390, because the break_lock field is also set by the waiters, and can potentially remain set indefinitely if no other CPUs come in to take the lock after it has been released. This patch removes the explicit spinning on break_lock from the waiters, instead relying on the outer trylock operation to determine when the lock is available. Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Peter Zijlstra Cc: Ingo Molnar Fixes: a8a217c22116 ("locking/core: Remove {read,spin,write}_can_lock()") Reported-by: Sebastian Ott Tested-by: Sebastian Ott Signed-off-by: Will Deacon --- kernel/locking/spinlock.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c index 1fd1a7543cdd..0ebb253e2199 100644 --- a/kernel/locking/spinlock.c +++ b/kernel/locking/spinlock.c @@ -68,8 +68,8 @@ void __lockfunc __raw_##op##_lock(locktype##_t *lock) \ \ if (!(lock)->break_lock) \ (lock)->break_lock = 1; \ - while ((lock)->break_lock) \ - arch_##op##_relax(&lock->raw_lock); \ + \ + arch_##op##_relax(&lock->raw_lock); \ } \ (lock)->break_lock = 0; \ } \ @@ -88,8 +88,8 @@ unsigned long __lockfunc __raw_##op##_lock_irqsave(locktype##_t *lock) \ \ if (!(lock)->break_lock) \ (lock)->break_lock = 1; \ - while ((lock)->break_lock) \ - arch_##op##_relax(&lock->raw_lock); \ + \ + arch_##op##_relax(&lock->raw_lock); \ } \ (lock)->break_lock = 0; \ return flags; \ -- 2.1.4