linux-kernel - Re: [PATCH v4a 00/38] timers: Use timer

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Message-ID: <20221105141817.GF1606271@roeck-us.net>
Date:   Sat, 5 Nov 2022 07:18:17 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>, rcu@...r.kernel.org,
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Subject: Re: [PATCH v4a 00/38] timers: Use timer_shutdown*() before freeing
 timers

On Sat, Nov 05, 2022 at 02:00:24AM -0400, Steven Rostedt wrote:
> 
> Back in April, I posted an RFC patch set to help mitigate a common issue
> where a timer gets armed just before it is freed, and when the timer
> goes off, it crashes in the timer code without any evidence of who the
> culprit was. I got side tracked and never finished up on that patch set.
> Since this type of crash is still our #1 crash we are seeing in the field,
> it has become a priority again to finish it.
> 
> The last version of that patch set is here:
> 
>   https://lore.kernel.org/all/20221104054053.431922658@goodmis.org/
> 
> I'm calling this version 4a as it only has obvious changes were the timer that
> is being shutdown is in the same function where it will be freed or released,
> as this series should be "safe" for adding. I'll be calling the other patches
> 4b for the next merge window.
> 

Just in case you didn't notice:

Looking through the resulting code, I think some of the remaining
calls to del_singleshot_timer_sync() can be converted as well.

The calls in drivers/staging/wlan-ng/prism2usb.c:prism2sta_disconnect_usb()
are obvious (the containing data structure is freed in the same function).
For drivers/char/tpm/tpm-dev-common.c:tpm_common_release(), the containing
data structure is freed in the calling code.

Thanks,
Guenter