From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757430AbcJGPo2 (ORCPT ); Fri, 7 Oct 2016 11:44:28 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:52594 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756794AbcJGPoR (ORCPT ); Fri, 7 Oct 2016 11:44:17 -0400 Date: Fri, 7 Oct 2016 17:43:51 +0200 From: Peter Zijlstra To: Linus Torvalds , Waiman Long , Jason Low , Ding Tianhong , Thomas Gleixner , Will Deacon , Ingo Molnar , Imre Deak , Linux Kernel Mailing List , Davidlohr Bueso , Tim Chen , Terry Rudd , "Paul E. McKenney" Cc: Chris Wilson , Daniel Vetter , Rob Clark Subject: Re: [PATCH -v4 1/8] locking/drm: Kill mutex trickery Message-ID: <20161007154351.GL3117@twins.programming.kicks-ass.net> References: <20161007145243.361481786@infradead.org> <20161007150210.927453282@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161007150210.927453282@infradead.org> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 07, 2016 at 04:52:44PM +0200, Peter Zijlstra wrote: > Poking at lock internals is not cool. Since I'm going to change the > implementation this will break, take it out. So something like the below would serve as a replacement for your previous hacks. Is this API something acceptable to people? Ingo, Thomas? --- include/linux/mutex.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 4d3bccabbea5..afcff2c85957 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -189,4 +189,29 @@ extern void mutex_unlock(struct mutex *lock); extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); +enum mutex_trylock_recursive_enum { + mutex_trylock_failed = 0, + mutex_trylock_success = 1, + mutex_trylock_recursive, +}; + +/** + * mutex_trylock_recursive - trylock variant that allows recursive locking + * @lock: mutex to be locked + * + * + * Returns: + * mutex_trylock_failed - trylock failed, + * mutex_trylock_success - lock acquired, + * mutex_trylock_recursive - we already owned the lock. + */ +static inline enum mutex_trylock_recursive_enum +mutex_trylock_recursive(struct mutex *lock) +{ + if (unlikely(__mutex_owner(lock) == current)) + return mutex_trylock_recursive; + + return mutex_trylock(lock); +} + #endif /* __LINUX_MUTEX_H */