linux-kernel - Re: [PATCH] panic: Ensure preemption is disabled during panic()

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Message-ID: <nycvar.YEU.7.76.1910071000170.15186@gjva.wvxbf.pm>
Date:   Mon, 7 Oct 2019 10:02:11 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Will Deacon <will@...nel.org>
cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Petr Mladek <pmladek@...e.com>,
        Kees Cook <keescook@...omium.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Feng Tang <feng.tang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-kernel@...ts.infradead.org,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, contact@...ium.me
Subject: Re: [PATCH] panic: Ensure preemption is disabled during panic()

On Fri, 4 Oct 2019, Will Deacon wrote:

> Indeed, and I think the LED blinking is already unreliable if the
> brightness operation needs to sleep. 

One thing is that led_set_brightness() can probably be forced to avoid the 
workqueue scheduling, by setting LED_BLINK_SW on the device (e.g. by 
issuing led_set_software_blink() during panic).

But I am afraid this still won't solve the issue completely, as USB 
keyboards need workqueues for blinking the LEDs in for URB management.

-- 
Jiri Kosina
SUSE Labs