From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932097AbeB1Kjw (ORCPT ); Wed, 28 Feb 2018 05:39:52 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:37286 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752150AbeB1Kju (ORCPT ); Wed, 28 Feb 2018 05:39:50 -0500 X-Google-Smtp-Source: AG47ELtqFHYg1AjYK+QBTvdvFbdeRnzzrHVShUzfoAU027o326crPwqQ3fRsL1yw019+tdUsG/zUIA== From: Andrea Parri To: linux-kernel@vger.kernel.org Cc: Andrea Parri , Alan Stern , Will Deacon , Peter Zijlstra , Boqun Feng , Nicholas Piggin , David Howells , Jade Alglave , Luc Maranget , "Paul E. McKenney" , Akira Yokosawa Subject: [PATCH] Documentation/locking: Document the semantics of spin_is_locked() Date: Wed, 28 Feb 2018 11:39:32 +0100 Message-Id: <1519814372-19941-1-git-send-email-parri.andrea@gmail.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There appeared to be a certain, recurrent uncertainty concerning the semantics of spin_is_locked(), likely a consequence of the fact that this semantics remains undocumented or that it has been historically linked to the (likewise unclear) semantics of spin_unlock_wait(). Document this semantics. Signed-off-by: Andrea Parri Cc: Alan Stern Cc: Will Deacon Cc: Peter Zijlstra Cc: Boqun Feng Cc: Nicholas Piggin Cc: David Howells Cc: Jade Alglave Cc: Luc Maranget Cc: "Paul E. McKenney" Cc: Akira Yokosawa --- include/linux/spinlock.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 4894d322d2584..2639fdc9a916c 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -380,6 +380,17 @@ static __always_inline int spin_trylock_irq(spinlock_t *lock) raw_spin_trylock_irqsave(spinlock_check(lock), flags); \ }) +/** + * spin_is_locked() - Check whether a spinlock is locked. + * @lock: Pointer to the spinlock. + * + * This function is NOT required to provide any memory ordering + * guarantees; it could be used for debugging purposes or, when + * additional synchronization is needed, accompanied with other + * constructs (memory barriers) enforcing the synchronization. + * + * Return: 1, if @lock is (found to be) locked; 0, otherwise. + */ static __always_inline int spin_is_locked(spinlock_t *lock) { return raw_spin_is_locked(&lock->rlock); -- 2.7.4