linux-kernel - Re: [PATCH RT 1/2] tasklet: Address a race resulting in double-enqueue

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Date:   Tue, 09 Jun 2020 19:40:03 +0300
From:   Ramon Fried <rfried.dev@...il.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Tom Zanussi <zanussi@...nel.org>
CC:     LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        John Kacur <jkacur@...hat.com>, Daniel Wagner <wagi@...om.org>,
        Clark Williams <williams@...hat.com>,
        Zhang Xiao <xiao.zhang@...driver.com>
Subject: Re: [PATCH RT 1/2] tasklet: Address a race resulting in double-enqueue



On June 9, 2020 7:37:31 PM GMT+03:00, Ramon Fried <rfried.dev@...il.com> wrote:
>
>
>On June 9, 2020 7:34:46 PM GMT+03:00, Sebastian Andrzej Siewior
><bigeasy@...utronix.de> wrote:
>>On 2020-06-09 11:17:53 [-0500], Tom Zanussi wrote:
>>> Hi Sebastian,
>>Hi Tom,
>>
>>> I did find a problem with the patch when configured as !SMP since in
>>> that case the RUN flag is never set (will send a patch for that
>>> shortly), but that wouldn't be the case here.
>>
>>How?
>>
>>| #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
>>| static inline int tasklet_trylock(struct tasklet_struct *t)
>>| {
>>|         return !test_and_set_bit(TASKLET_STATE_RUN, &(t)->state);
>>| }
>>
>>I can't tell from the backtrace if he runs with RT or without but I
>>assumed RT. But yes, for !SMP && !RT it would explain it.
>PREEMT_FULL is enabled. 
>I'm working on getting symbols for this trace, this is a crash kernel
>so everything is stripped naked. 
>Thanks, Ramon

Correction. normal kernel is running with RT enabled, crash kernel without. 
>>
>>> It would help to be able to reproduce it, but I haven't been able to
>>> yet.
>>> 
>>> Tom
>>> 
>>Sebastian

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