linux-kernel - Re: [PATCH] locking/rwsem: Add up_write_non_owner() for percpu_up

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Message-ID: <63c13bd6-7f42-7d3f-3cda-f989f6982ae4@redhat.com>
Date:   Mon, 14 May 2018 15:36:41 -0400
From:   Waiman Long <longman@...hat.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Davidlohr Bueso <dave@...olabs.net>,
        "Theodore Y. Ts'o" <tytso@....edu>
Subject: Re: [PATCH] locking/rwsem: Add up_write_non_owner() for
 percpu_up_write()

On 04/09/2018 10:22 AM, Oleg Nesterov wrote:
> On 04/09, Waiman Long wrote:
>> On 04/09/2018 07:20 AM, Oleg Nesterov wrote:
>>> Hmm. Can you look at lockdep_sb_freeze_release() and lockdep_sb_freeze_acquire()?
>> These 2 functions are there to deal with the lockdep code.
> Plus they clearly document why sem->owner check is not right when it comes
> to super_block->s_writers[]. Not only freeze and thaw can be called by
> different processes, we need to return to user-space with rwsem held for
> writing.

Sorry for the late reply as I was busy on other work.

I have just sent out a v2 patch to hopefully address your concern.
Please let me know your thought on that.

Thanks,
Longman