linux-kernel - Re: [PATCH 1/6] sched/wait: Add swq_has

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]

Date:   Wed, 11 Oct 2017 13:21:47 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Davidlohr Bueso <dave@...olabs.net>
Cc:     mingo@...hat.com, npiggin@...il.com, paulmck@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/6] sched/wait: Add swq_has_sleepers()

On 11/10/2017 10:27, Peter Zijlstra wrote:
> On Tue, Sep 05, 2017 at 12:00:17PM -0700, Davidlohr Bueso wrote:
>> Which is the equivalent of what we have in regular waitqueues.
>> I'm not crazy about the name, but this also helps us get both
>> apis closer -- which iirc comes originally from the -net folks.
> 
> I'm confused. I don't see anything like this in the original waitqueue.
> 

/**
 * wq_has_sleeper - check if there are any waiting processes
 * @wq_head: wait queue head
 *
 * Returns true if wq_head has waiting processes
 *
 * Please refer to the comment for waitqueue_active.
 */
static inline bool wq_has_sleeper(struct wait_queue_head *wq_head)
{
        /*
         * We need to be sure we are in sync with the
         * add_wait_queue modifications to the wait queue.
         *
         * This memory barrier should be paired with one on the
         * waiting side.
         */
        smp_mb();
        return waitqueue_active(wq_head);
}

Paolo