From: Neeraj Upadhyay <neeraju@codeaurora.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: josh@joshtriplett.org, peterz@infradead.org, mingo@kernel.org,
jiangshanlai@gmail.com, dzickus@redhat.com,
brendan.jackman@arm.com, malat@debian.org,
linux-kernel@vger.kernel.org, sramana@codeaurora.org,
linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] cpu/hotplug: Fix rollback during error-out in takedown_cpu()
Date: Thu, 6 Sep 2018 08:26:20 +0530 [thread overview]
Message-ID: <9cac90ff-1a43-8663-da2e-7191975b5e93@codeaurora.org> (raw)
In-Reply-To: <alpine.DEB.2.21.1809051514070.1416@nanos.tec.linutronix.de>
On 09/05/2018 06:47 PM, Thomas Gleixner wrote:
> On Wed, 5 Sep 2018, Neeraj Upadhyay wrote:
>> On 09/05/2018 05:53 PM, Thomas Gleixner wrote:
>>> And looking closer this is a general issue. Just that the TEARDOWN state
>>> makes it simple to observe. It's universaly broken, when the first teardown
>>> callback fails because, st->state is only decremented _AFTER_ the callback
>>> returns success, but undo_cpu_down() increments unconditionally.
>>>
>> As per my understanding, there are 2 problems here; one is fixed with your
>> patch, and other is cpuhp_reset_state() is used during rollback from non-AP to
>> AP state, which seem to result in 2 increments of st->state (one increment
>> done by cpuhp_reset_state() and another by cpu_thread_fun()) .
> And how did your hack fix that up magically? I'll have a look later today.
>
> Thanks,
>
> tglx
The hack fixes it by not calling cpuhp_reset_state() and doing rollback
state reset inline in _cpu_down().
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation
next prev parent reply other threads:[~2018-09-06 2:56 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-04 6:33 [PATCH] cpu/hotplug: Fix rollback during error-out in takedown_cpu() Neeraj Upadhyay
2018-09-04 12:12 ` Mukesh Ojha
2018-09-05 11:33 ` Thomas Gleixner
2018-09-05 12:09 ` Mukesh Ojha
2018-09-05 13:14 ` Thomas Gleixner
2018-09-05 12:23 ` Thomas Gleixner
2018-09-05 12:51 ` Neeraj Upadhyay
2018-09-05 13:17 ` Thomas Gleixner
2018-09-06 2:56 ` Neeraj Upadhyay [this message]
2018-09-06 8:18 ` Thomas Gleixner
2018-09-06 9:00 ` Neeraj Upadhyay
2018-09-05 14:53 ` Sudeep Holla
2018-09-05 15:19 ` Geert Uytterhoeven
2018-09-06 13:52 ` [tip:smp/urgent] cpu/hotplug: Prevent state corruption on error rollback tip-bot for Thomas Gleixner
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