Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754704AbbGTK6X (ORCPT ); Mon, 20 Jul 2015 06:58:23 -0400 Received: from terminus.zytor.com ([198.137.202.10]:55789 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753183AbbGTK6W (ORCPT ); Mon, 20 Jul 2015 06:58:22 -0400 Date: Mon, 20 Jul 2015 03:57:37 -0700 From: tip-bot for Davidlohr Bueso Message-ID: Cc: darren@dvhart.com, dave@stgolabs.net, dbueso@suse.de, tglx@linutronix.de, hpa@zytor.com, mingo@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org Reply-To: hpa@zytor.com, mingo@kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org, darren@dvhart.com, dave@stgolabs.net, dbueso@suse.de, tglx@linutronix.de In-Reply-To: <1435645562-975-2-git-send-email-dave@stgolabs.net> References: <1435645562-975-2-git-send-email-dave@stgolabs.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/core] futex: Enhance comments in futex_lock_pi() for blocking paths Git-Commit-ID: 767f509ca11269c2bcd92e3972a93096f2173ac0 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 Content-Length: 2218 Lines: 56 Commit-ID: 767f509ca11269c2bcd92e3972a93096f2173ac0 Gitweb: http://git.kernel.org/tip/767f509ca11269c2bcd92e3972a93096f2173ac0 Author: Davidlohr Bueso AuthorDate: Mon, 29 Jun 2015 23:26:01 -0700 Committer: Thomas Gleixner CommitDate: Mon, 20 Jul 2015 11:45:45 +0200 futex: Enhance comments in futex_lock_pi() for blocking paths ... serves a bit better to clarify between blocking and non-blocking code paths. Signed-off-by: Davidlohr Bueso Cc: Peter Zijlstra Cc: Darren Hart Cc: Davidlohr Bueso Link: http://lkml.kernel.org/r/1435645562-975-2-git-send-email-dave@stgolabs.net Signed-off-by: Thomas Gleixner --- kernel/futex.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index c4a182f..153eb22 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2268,8 +2268,11 @@ static long futex_wait_restart(struct restart_block *restart) /* * Userspace tried a 0 -> TID atomic transition of the futex value * and failed. The kernel side here does the whole locking operation: - * if there are waiters then it will block, it does PI, etc. (Due to - * races the kernel might see a 0 value of the futex too.) + * if there are waiters then it will block as a consequence of relying + * on rt-mutexes, it does PI, etc. (Due to races the kernel might see + * a 0 value of the futex too.). + * + * Also serves as futex trylock_pi()'ing, and due semantics. */ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock) @@ -2300,6 +2303,10 @@ retry_private: ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); if (unlikely(ret)) { + /* + * Atomic work succeeded and we got the lock, + * or failed. Either way, we do _not_ block. + */ switch (ret) { case 1: /* We got the lock. */ -- 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/