linux-kernel - Re: sem_lock() vs qspinlocks

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20160520205222.GI3193@twins.programming.kicks-ass.net>
Date:	Fri, 20 May 2016 22:52:22 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Waiman Long <waiman.long@....com>
Cc:	Davidlohr Bueso <dave@...olabs.net>, manfred@...orfullife.com,
	mingo@...nel.org, torvalds@...ux-foundation.org,
	ggherdovich@...e.com, mgorman@...hsingularity.net,
	linux-kernel@...r.kernel.org
Subject: Re: sem_lock() vs qspinlocks

On Fri, May 20, 2016 at 04:47:43PM -0400, Waiman Long wrote:

> >Similarly, and I know you hate it, but afaict, then semantically
> >queued_spin_is_contended() ought to be:
> >
> >-       return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
> >+       return atomic_read(&lock->val);
> >

> Looking for contended lock, you need to consider the lock waiters also. So
> looking at the whole word is right.

No, you _only_ need to look at the lock waiters.