Messages in this thread | | | Subject | Re: [PATCH 5/5] perf/arm_dsu: Fix CPU hotplug races | From | Robin Murphy <> | Date | Tue, 5 Feb 2019 13:04:23 +0000 |
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Hi Suzuki,
On 05/02/2019 11:40, Suzuki K Poulose wrote: > 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@arm.com> > > Should we add : > > Fixes: commit 7520fa99246dade7ab6 ("perf: ARM DynamIQ Shared Unit PMU > support") > > Either way: > > Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Thanks for the reviews! I think this patch is worthwhile for cleanliness and consistency, but since it's neither self-contained (with the dependency on #4) nor "fix[ing] a real bug that bothers people" I'm not convinced it really deserves backporting - unlike the preemption issue, actually getting a crash from this race in practice is unlikely enough that it would probably require some determined, deliberate effort to trigger it with just the right conditions.
Cheers, Robin.
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