linux-kernel - Re: [PATCH] MIPS: Fix idle VS timer enqueue

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: <Z6831Oh38UwORCkj@pavilion.home>
Date: Fri, 14 Feb 2025 13:32:20 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Marco Crivellari <marco.crivellari@...e.com>
Cc: linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] MIPS: Fix idle VS timer enqueue

Le Fri, Feb 14, 2025 at 11:50:47AM +0100, Marco Crivellari a écrit :
> MIPS re-enables interrupts on its idle routine and performs
> a TIF_NEED_RESCHED check afterwards before putting the CPU to sleep.
> 
> The IRQs firing between the check and the 'wait' instruction may set the
> TIF_NEED_RESCHED flag. In order to deal with this possible race, IRQs
> interrupting __r4k_wait() rollback their return address to the
> beginning of __r4k_wait() so that TIF_NEED_RESCHED is checked
> again before going back to sleep.
> 
> However idle IRQs can also queue timers that may require a tick
> reprogramming through a new generic idle loop iteration but those timers
> would go unnoticed here because __r4k_wait() only checks
> TIF_NEED_RESCHED. It doesn't check for pending timers.
> 
> Fix this with fast-forwarding idle IRQs return address to the end of the
> idle routine instead of the beginning, so that the generic idle loop
> handles both TIF_NEED_RESCHED and pending timers.
> 
> Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>

Acked-by: Frederic Weisbecker <frederic@...nel.org>

Thanks a lot!