linux-kernel - Re: [PATCH] locking/rtmutex: Do the trylock-slowpath with DEBUG_RT

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Message-ID: <20230424084259.txfDjYNV@linutronix.de>
Date:   Mon, 24 Apr 2023 10:42:59 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, Crystal Wood <swood@...hat.com>,
        John Keeping <john@...anate.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH] locking/rtmutex: Do the trylock-slowpath with
 DEBUG_RT_MUTEXES enabled.

On 2023-04-21 19:58:52 [+0200], Thomas Gleixner wrote:
> On Tue, Mar 28 2023 at 18:54, Sebastian Andrzej Siewior wrote:
> > On 2023-03-22 17:27:21 [+0100], To Thomas Gleixner wrote:
> >> > Aside of that for CONFIG_DEBUG_RT_MUTEXES=y builds it flushes on every
> >> > lock operation whether the lock is contended or not.
> >> 
> >> For mutex & ww_mutex operations. rwsem is not affected by
> >> CONFIG_DEBUG_RT_MUTEXES. As for mutex it could be mitigated by invoking
> >> try_to_take_rt_mutex() before blk_flush_plug().
> 
> > I haven't observed anything in the ww-mutex path so we can ignore it or
> > do something similar to this.
> 
> Yay for consistency !
> 
> I fixed it up to the below.

you fixed the ww-mutex path and did with the debug path what I did in
the follow-up patch. Let me fold this then and drop the other one.

> Thanks,
> 
>         tglx

Sebastian