linux-kernel - Re: [PATCH v8 8/8] rcu/tree: Setschedule gp ktread to SCHED

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Message-ID: <20190701191308.GE3402@hirez.programming.kicks-ass.net>
Date:   Mon, 1 Jul 2019 21:13:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     mingo@...hat.com, rostedt@...dmis.org, tj@...nel.org,
        linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org, lizefan@...wei.com,
        cgroups@...r.kernel.org
Subject: Re: [PATCH v8 8/8] rcu/tree: Setschedule gp ktread to SCHED_FIFO
 outside of atomic region

On Fri, Jun 28, 2019 at 10:06:18AM +0200, Juri Lelli wrote:
> sched_setscheduler() needs to acquire cpuset_rwsem, but it is currently
> called from an invalid (atomic) context by rcu_spawn_gp_kthread().
> 
> Fix that by simply moving sched_setscheduler_nocheck() call outside of
> the atomic region, as it doesn't actually require to be guarded by
> rcu_node lock.

Maybe move this earlier in the series such that the bug doesn't manifest
in bisection?