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Groups > linux.kernel > #1682354
| From | Juri Lelli <juri.lelli@arm.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask cpus_to_visit |
| Date | 2017-07-06 13:00 +0200 |
| Message-ID | <u0cFP-3bQ-7@gated-at.bofh.it> (permalink) |
| References | <u0bJL-2Bf-3@gated-at.bofh.it> <u0bJN-2Bf-41@gated-at.bofh.it> <u0ccN-32q-11@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Hi Viresh,
On 06/07/17 15:52, Viresh Kumar wrote:
> On 06-07-17, 10:49, Dietmar Eggemann wrote:
[...]
> > static void parsing_done_workfn(struct work_struct *work)
> > {
> > + free_cpumask_var(cpus_to_visit);
> > cpufreq_unregister_notifier(&init_cpu_capacity_notifier,
> > CPUFREQ_POLICY_NOTIFIER);
>
> As a general rule (and good coding practice), it is better to free resources
> only after the users are gone. And so we should have changed the order here.
> i.e. Unregister the notifier first and then free the cpumask.
>
> And because of that we may end up crashing the kernel here.
>
> Here is an example:
>
> Consider that init_cpu_capacity_callback() is getting called concurrently on big
> and LITTLE CPUs.
>
>
> CPU0 (big) CPU4 (LITTLE)
>
> if (cap_parsing_failed || cap_parsing_done)
> return 0;
>
But, in this case the policy notifier for LITTLE cluster has not been
executed yet, so the domain's CPUs have not yet been cleared out from
cpus_to_visit. CPU0 won't see the mask as empty then, right?
> cap_parsing_done = true;
> schedule_work(&parsing_done_work);
>
> parsing_done_workfn(work)
> -> free_cpumask_var(cpus_to_visit);
> -> cpufreq_unregister_notifier()
>
>
> switch (val) {
> ...
> /* Touch cpus_to_visit and crash */
>
>
> My assumption here is that the same notifier head can get called in parallel on
> two CPUs as all I see there is a down_read() in __blocking_notifier_call_chain()
> which shouldn't block parallel calls.
>
If that's the case I'm wondering however if we need explicit
synchronization though. Otherwise both threads can read the mask as
full, clear only their bits and not schedule the workfn?
But, can the policies be concurrently initialized? Or is the
initialization process serialized or the different domains?
Thanks,
- Juri
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[PATCH v2 00/10] arm, arm64: frequency- and cpu-invariant accounting support for task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
[PATCH v2 08/10] arm64: wire frequency-invariant accounting support up to the task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 08/10] arm64: wire frequency-invariant accounting support up to the task scheduler Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
[PATCH v2 03/10] drivers base/arch_topology: frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 03/10] drivers base/arch_topology: frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
Re: [PATCH v2 03/10] drivers base/arch_topology: frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-07 19:00 +0200
[PATCH v2 05/10] arm: wire frequency-invariant accounting support up to the task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 05/10] arm: wire frequency-invariant accounting support up to the task scheduler Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
[PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-07 00:50 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-07 18:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rafael@kernel.org> - 2017-07-07 18:20 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-07 19:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-08 14:20 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-10 09:00 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-10 15:00 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-11 08:50 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-11 17:30 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 14:50 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-13 15:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 16:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-10 11:40 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-10 11:50 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-10 12:40 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-10 14:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-11 08:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-11 17:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-11 17:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-11 17:20 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-12 06:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-12 10:40 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-12 11:30 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-12 13:20 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-13 01:30 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-13 10:00 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-13 10:50 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-13 13:20 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 16:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-13 16:50 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 17:10 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 15:00 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 14:50 +0200
Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-10 08:50 +0200
[PATCH v2 04/10] arm: wire cpufreq input data for frequency-invariant accounting up to the arch Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 04/10] arm: wire cpufreq input data for frequency-invariant accounting up to the arch Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
Re: [PATCH v2 04/10] arm: wire cpufreq input data for frequency-invariant accounting up to the arch Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-10 17:20 +0200
Re: [PATCH v2 04/10] arm: wire cpufreq input data for frequency-invariant accounting up to the arch Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-11 08:40 +0200
[PATCH v2 09/10] arm64: wire cpu-invariant accounting support up to the task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 09/10] arm64: wire cpu-invariant accounting support up to the task scheduler Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
[PATCH v2 06/10] arm: wire cpu-invariant accounting support up to the task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 06/10] arm: wire cpu-invariant accounting support up to the task scheduler Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
[PATCH v2 01/10] drivers base/arch_topology: free cpumask cpus_to_visit Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask cpus_to_visit Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:30 +0200
Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask cpus_to_visit Juri Lelli <juri.lelli@arm.com> - 2017-07-06 13:00 +0200
Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask cpus_to_visit Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 13:20 +0200
Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask cpus_to_visit Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-07 18:00 +0200
[PATCH v2 10/10] drivers base/arch_topology: inline cpu- and frequency-invariant accounting Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
Re: [PATCH v2 10/10] drivers base/arch_topology: inline cpu- and frequency-invariant accounting Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 13:00 +0200
Re: [PATCH v2 10/10] drivers base/arch_topology: inline cpu- and frequency-invariant accounting Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-10 17:20 +0200
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