linux-kernel - Re: [PATCH 1/4] locking/rtmutex: Implement lockless top-waiter wakeup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.11.1506051434580.7723@nanos>
Date:	Fri, 5 Jun 2015 14:35:32 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Davidlohr Bueso <dave@...olabs.net>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/4] locking/rtmutex: Implement lockless top-waiter
 wakeup

On Tue, 19 May 2015, Davidlohr Bueso wrote:

> Mark the task for later wakeup after the wait_lock has been released.
> This way, once the next task is awoken, it will have a better chance
> to of finding the wait_lock free when continuing executing in
> __rt_mutex_slowlock() when trying to acquire the rtmutex, calling
> try_to_take_rt_mutex(). Upon contended scenarios, other tasks attempting
> take the lock may acquire it first, right after the wait_lock is released,
> but (a) this can also occur with the current code, as it relies on the
> spinlock fairness, and (b) we are dealing with the top-waiter anyway,
> so it will always take the lock next.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/