linux-kernel - Re: [PATCH v2 2/3] locking/rwsem: disable preemption for spinning region

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Date:   Fri, 15 Oct 2021 12:20:30 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yanfei Xu <yanfei.xu@...driver.com>
Cc:     mingo@...hat.com, will@...nel.org, longman@...hat.com,
        boqun.feng@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] locking/rwsem: disable preemption for spinning
 region

On Fri, Oct 15, 2021 at 12:13:59PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 13, 2021 at 09:41:53PM +0800, Yanfei Xu wrote:
> > The spinning region rwsem_spin_on_owner() should not be preempted,
> > however the rwsem_down_write_slowpath() invokes it and don't disable
> > preemption. Fix it by adding a pair of preempt_disable/enable().
> 
> I'm thinking we should do this patch before #1, otherwise we have a
> single patch window where we'll trigger the assertion, no?

Anyway, I've stuck the lot (reordered) into my locking/core branch, lets
see what the robots make of it ;-)