linux-kernel - Re: [PATCH 5/5] perf/arm_dsu: Fix CPU hotplug races

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Message-ID: <9fcf862c-0d07-cece-852f-6c09128aa0c5@arm.com>
Date:   Tue, 5 Feb 2019 11:40:31 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     robin.murphy@....com, will.deacon@....com, mark.rutland@....com
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        peterz@...radead.org, tglx@...utronix.de, bigeasy@...utronix.de
Subject: Re: [PATCH 5/5] perf/arm_dsu: Fix CPU hotplug races



On 04/02/2019 17:09, Robin Murphy wrote:
> Like other system PMUs which associate themselves with an arbitrary CPU
> for housekeeping purposes, arm_dsu has a race between registering the
> hotplug notifier and registering the PMU device, such that the hotplug
> niotifier can potentially fire and attempt to migrate the PMU context
> before the latter is valid. This is easily resolved by inhibiting
> hotplug until both the notifier and PMU device are successfully set up.
> 
> For the same reason, also suppress any synchronous notifier calls in the
> cleanup path if PMU registration fails.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>

Should we add :

Fixes: commit 7520fa99246dade7ab6 ("perf: ARM DynamIQ Shared Unit PMU support")

Either way:

Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>