linux-kernel - Re: [ANNOUNCE] v4.14.29-rt25

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Message-ID: <764d0abc-7e88-a696-17a0-0bf807148d5b@ti.com>
Date:   Mon, 23 Apr 2018 11:57:39 -0500
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [ANNOUNCE] v4.14.29-rt25



On 04/20/2018 12:11 PM, Sebastian Andrzej Siewior wrote:
> On 2018-03-27 13:01:07 [-0500], Grygorii Strashko wrote:
>> Hi Sebastian,
> Hi Grygorii,
> 
>> I've took this RT version and applied "[RT] kernel/time/posix-timer: avoid schedule()
>> while holding the RCU lock" [1] on top. Then I run below tests:
> …
>> no stall or crashes were observed, but I've caught two "rcu_note_context_switch()" warnings
> 
> the warning is unrelated to the patch I posted. This should mute it:
> 
> Subject: [PATCH RT] rtmutex: annotate sleeping lock context
> 
> The RCU code complains on schedule() within a rcu_readlock() section.
> The valid scenario on -RT is if a sleeping is held. In order to suppress
> the warning the mirgrate_disable counter was used to identify the
> invocation of schedule() due to lock contention.
> 
> Grygorii Strashko report that during CPU hotplug we might see the
> warning via
>   rt_spin_lock() -> migrate_disable() -> pin_current_cpu() -> __read_rt_lock()
> 
> because the counter is not yet set.
> It is also possible to trigger the warning from cpu_chill()
> (seen on a kblockd_mod_delayed_work_on() caller).
> 
> To address this RCU warning I annotate the sleeping lock context. The
> counter is incremented before migrate_disable() so the warning Grygorii
> should not trigger anymore. Additionally I use that counter in
> cpu_chill() to avoid the RCU warning from there.

Sry, but I can't apply it. What's you base?

> 
> Reported-by: Grygorii Strashko <grygorii.strashko@...com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
-- 
regards,
-grygorii