linux-kernel - Re: [PATCH v4] locking/rwbase: Mitigate indefinite writer starvation

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Message-ID: <Y+0B+1q4cYpjUcgr@linutronix.de>
Date:   Wed, 15 Feb 2023 17:02:03 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Mel Gorman <mgorman@...hsingularity.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Linux-RT <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] locking/rwbase: Mitigate indefinite writer starvation

On 2023-02-06 15:30:35 [+0100], Thomas Gleixner wrote:
> What's the downside of actually forcing !RT readers into the slowpath
> once there is a writer waiting?

We always said that there are no RT users of rwsem. Therefore it
shouldn't matter because we still assume that nothing depends on this.
After all we had one a one reader implementation of rwsem and this is
the first report (to my knowledge) of a fallout since it was changed to
multi-reader.

That said let me update Mel's patch and resend it without this bit.

> Thanks,
> 
>         tglx

Sebastian