From: Nico Pache <npache@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Darren Hart" <dvhart@infradead.org>,
"Davidlohr Bueso" <dave@stgolabs.net>,
"André Almeida" <andrealmeid@collabora.com>,
"Arjan van de Ven" <arjan@infradead.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
"Matthew Wilcox" <willy@infradead.org>
Subject: Re: [RFC 2/3] futex: exit: Print a warning when futex_cleanup fails
Date: Fri, 22 Apr 2022 10:23:50 -0400 [thread overview]
Message-ID: <90124b02-76b5-d775-ac7d-a2e9d7677fa1@redhat.com> (raw)
In-Reply-To: <87r15qrwdt.ffs@tglx>
On 4/21/22 16:53, Thomas Gleixner wrote:
> On Thu, Apr 21 2022 at 15:05, Nico Pache wrote:
>
>> The futex_cleanup routines currently fails silently.
>>
>> Allow the futex_cleanup routines to fail more verbosely so we can
>> leave a message behind for easier debugging/error detecting.
>
> This is a free ticket to spam dmesg for any unpriviledged user.
As Matthew pointed out, we'd want to rate limit this. I was also thinking we can
limit this to debug kernels so unpriviledged users can not cause dmesg spamming
in production configs.
>
>> Fixes: 0771dfefc9e5 ("[PATCH] lightweight robust futexes: core")
>
> There is nothing to fix, really.
Fair enough, its been part of the design since inceptions.
>
> Robust futexes are best effort as I explained you before and spamming
> dmesg won't help anything.
It would have helped find the OOM/Robust Futex issue more quickly. It may also
help detect breakages in the pthread code (or any other users of robust futex)
if someone is doing something incorrectly.
Just a thought though. If you think its pointless to proceed down this path I
wont push forward.
Cheers,
-- Nico
next prev parent reply other threads:[~2022-04-22 14:24 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-21 19:05 [RFC 0/3] Slight improvements for OOM/Futex Nico Pache
2022-04-21 19:05 ` [RFC 1/3] mm: change vma_is_anonymous to vma_is_private_anon Nico Pache
2022-04-21 19:28 ` Matthew Wilcox
2022-04-22 14:00 ` Nico Pache
2022-04-28 16:14 ` David Hildenbrand
2022-04-21 19:05 ` [RFC 2/3] futex: exit: Print a warning when futex_cleanup fails Nico Pache
2022-04-21 19:30 ` Matthew Wilcox
2022-04-22 14:12 ` Nico Pache
2022-04-21 20:53 ` Thomas Gleixner
2022-04-22 14:23 ` Nico Pache [this message]
2022-04-22 14:42 ` Thomas Gleixner
2022-04-22 0:18 ` kernel test robot
2022-04-21 19:05 ` [RFC 3/3] exit: Check for MMF_OOM_SKIP in exit_mmap Nico Pache
2022-04-22 15:38 ` Michal Hocko
2022-04-25 19:00 ` Nico Pache
2022-04-26 6:59 ` Michal Hocko
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