Messages in this thread |  | | Date | Mon, 21 Oct 2019 07:46:26 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH v2] cpufreq: cancel any pending policy update work scheduled before freeing |
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On 18-10-19, 11:58, Sudeep Holla wrote: > Schedules policy update work may end up racing with the freeing of the > policy and unregistering the driver. > > One possible race is as below where the cpufreq_driver is unregistered > but the scheduled work gets executed at later stage when cpufreq_driver > is NULL(i.e. after freeing the policy and driver) > > Unable to handle kernel NULL pointer dereference at virtual address 0000001c > pgd = (ptrval) > [0000001c] *pgd=80000080204003, *pmd=00000000 > Internal error: Oops: 206 [#1] SMP THUMB2 > Modules linked in: > CPU: 0 PID: 34 Comm: kworker/0:1 Not tainted 5.4.0-rc3-00006-g67f5a8081a4b #86 > Hardware name: ARM-Versatile Express > Workqueue: events handle_update > PC is at cpufreq_set_policy+0x58/0x228 > LR is at dev_pm_qos_read_value+0x77/0xac > Control: 70c5387d Table: 80203000 DAC: fffffffd > Process kworker/0:1 (pid: 34, stack limit = 0x(ptrval)) > (cpufreq_set_policy) from (refresh_frequency_limits.part.24+0x37/0x48) > (refresh_frequency_limits.part.24) from (handle_update+0x2f/0x38) > (handle_update) from (process_one_work+0x16d/0x3cc) > (process_one_work) from (worker_thread+0xff/0x414) > (worker_thread) from (kthread+0xff/0x100) > (kthread) from (ret_from_fork+0x11/0x28) > > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > Cc: Viresh Kumar <viresh.kumar@linaro.org> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> > --- > drivers/cpufreq/cpufreq.c | 2 ++ > 1 file changed, 2 insertions(+) > > v1->v2: > - Dropped check for work_pending as it can still be racy > - Changed from flush_work to cancel_work_sync > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index e93cba29fbb2..8ad9c2859841 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -1279,6 +1279,8 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy) > } > > dev_pm_qos_remove_request(policy->min_freq_req); > + /* cancel any pending policy->update work before freeing the policy */ > + cancel_work_sync(&policy->update); > kfree(policy->min_freq_req); > > cpufreq_policy_put_kobj(policy);
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
-- viresh
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