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Date:   Tue, 9 Jun 2020 18:34:46 +0200
From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Tom Zanussi <zanussi@kernel.org>
Cc:     Ramon Fried <rfried.dev@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
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        John Kacur <jkacur@redhat.com>, Daniel Wagner <wagi@monom.org>,
        Clark Williams <williams@redhat.com>,
        Zhang Xiao <xiao.zhang@windriver.com>
Subject: Re: [PATCH RT 1/2] tasklet: Address a race resulting in
 double-enqueue
Message-ID: <20200609163446.efp76qbjzkbtl7nk@linutronix.de>
References: <cover.1587675252.git.zanussi@kernel.org>
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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.

> It would help to be able to reproduce it, but I haven't been able to
> yet.
> 
> Tom
> 
Sebastian