linux-kernel - Re: [BUG] -next lockdep invalid wait context

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]

Message-ID: <751e281a-126b-4bcd-8965-71affac4a783@suse.cz>
Date: Thu, 31 Oct 2024 09:18:52 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 "Paul E. McKenney" <paulmck@...nel.org>
Cc: Marco Elver <elver@...gle.com>, linux-next@...r.kernel.org,
 linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
 linux-mm@...ck.org, sfr@...b.auug.org.au, longman@...hat.com,
 boqun.feng@...il.com, cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
 iamjoonsoo.kim@....com, akpm@...ux-foundation.org
Subject: Re: [BUG] -next lockdep invalid wait context

On 10/31/24 08:55, Sebastian Andrzej Siewior wrote:
> On 2024-10-31 08:35:45 [+0100], Vlastimil Babka wrote:
>> On 10/31/24 08:21, Sebastian Andrzej Siewior wrote:
>> > On 2024-10-30 16:10:58 [-0700], Paul E. McKenney wrote:
>> >> 
>> >> So I need to avoid calling kfree() within an smp_call_function() handler?
>> > 
>> > Yes. No kmalloc()/ kfree() in IRQ context.
>> 
>> However, isn't this the case that the rule is actually about hardirq context
>> on RT, and most of these operations that are in IRQ context on !RT become
>> the threaded interrupt context on RT, so they are actually fine? Or is smp
>> call callback a hardirq context on RT and thus it really can't do those
>> operations?
> 
> interrupt handlers as of request_irq() are forced-threaded on RT so you
> can do kmalloc()/ kfree() there. smp_call_function.*() on the other hand
> are not threaded and invoked directly within the IRQ context.

Makes sense, thanks.

So how comes rcutorture wasn't deadlocking on RT already, is it (or RCU
itself) doing anything differently there that avoids the kfree() from
smp_call_function() handler?

>> Vlastimil
>> 
> Sebastian
>