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From: Thomas Gleixner <tglx@linutronix.de>
To: Prakruthi Deepak Heragu <pheragu@codeaurora.org>
Cc: linux-kernel@vger.kernel.org, tsoni@codeaurora.org,
	ckadabi@codeaurora.org, bryanh@codeaurora.org,
	psodagud@codeaurora.org
Subject: Re: [PATCH] kernel: cpu: Handle hotplug failure for state CPUHP_AP_IDLE_DEAD
Date: Thu, 6 Sep 2018 10:10:09 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1809060957540.1416@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1536174917-11408-1-git-send-email-pheragu@codeaurora.org>

On Wed, 5 Sep 2018, Prakruthi Deepak Heragu wrote:

> Once the tear down hotplug handler is run, cpu is dead and enters
> into CPUHP_AP_IDLE_DEAD state. Any callbacks that fail in the state
> machine with state < CPUHP_AP_IDLE must be treated as fatal as this
> could result into timer not beig migrated away from dead cpu and run
> into issues like work queue lock ups, sched_clock timer wrapping to
> zero as sched_clock_poll which is in the hrtimer base of cpu being
> hotplugged does not get migrated.

BUG_ON() is the last resort when there is no other way out. And there is no
reason to treat such a failure as fatal unconditionally.

Why would any of those callback fail at all? And if that ever happens, then
we really can be smarter than just giving up.

Thanks,

	tglx



      reply	other threads:[~2018-09-06  8:10 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-05 19:15 [PATCH] kernel: cpu: Handle hotplug failure for state CPUHP_AP_IDLE_DEAD Prakruthi Deepak Heragu
2018-09-06  8:10 ` Thomas Gleixner [this message]

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