linux-kernel - Re: [RFC PATCH 02/21] Add a prelocked wake-up

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Message-ID: <20274.1571178796@warthog.procyon.org.uk>
Date:   Tue, 15 Oct 2019 23:33:16 +0100
From:   David Howells <dhowells@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     dhowells@...hat.com, Tim Chen <tim.c.chen@...ux.intel.com>,
        Kan Liang <kan.liang@...el.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>, raven@...maw.net,
        Christian Brauner <christian@...uner.io>,
        keyrings@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-block <linux-block@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 02/21] Add a prelocked wake-up

Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> > Add a wakeup call for a case whereby the caller already has the waitqueue
> > spinlock held.
> 
> That naming is crazy.

Sorry, yeah.  This is a bit hacked together at the moment and needs some more
tidying up.  I've had a lot of problems with performance regressions of up to
40% from seemingly simple changes involving moving locks around - it turns out
that the problem was that I was running with kasan enabled.

David