linux-kernel - Re: [RT WARNING] DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current) with fsfreeze (4.19.25-rt16)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 2 May 2019 13:42:59 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Clark Williams <williams@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>, jack@...e.com,
        Waiman Long <longman@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [RT WARNING] DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) !=
 current) with fsfreeze (4.19.25-rt16)

On 05/02, Oleg Nesterov wrote:
>
> But this all is cosmetic, it seems that we can remove ->rw_sem altogether
> but I am not sure...

I mean, afaics percpu_down_read() can just do

	wait_event(readers_block == 0);

in the slow path, while percpu_down_write()

	wait_even_exclusive(xchg(readers_block, 1) == 0);

we do not really need ->rw_sem if we rely on wait_queue_head.


But in fact, either way it seems that we going to implement another simple
"non owner" read/write lock, so perhaps we should do this explicitly?

Oleg.