| Message ID | 1452533760-13787-17-git-send-email-juri.lelli@arm.com (mailing list archive) |
|---|---|
| State | RFC |
| Headers | show |
On 11-01-16, 17:35, Juri Lelli wrote: > There are no good reasons why policy->rwsem cannot be hold across calls to > __cpufreq_governor with CPUFREQ_GOV_POLICY_EXIT event. > > Remove {up,down}_write across such call sites. This also verify assertion > that policy->rwsem is always hold when calling into __cpufreq_governor. Test on X86 with prove_locking etc enabled.. and try running tests from my cpufreq-test repo. There were real concerns. Over that, I have identified the issue completely, as to why the ABBA dependency I mentioned earlier is there. You can find that in the branch I shared with you earlier. commit 57714d5b1778 ("cpufreq: Access governor's sysfs attributes without 'policy->rwsem'")
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index d58a622..797bfae 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -2182,9 +2182,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy, return ret; } - up_write(&policy->rwsem); ret = __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT); - down_write(&policy->rwsem); if (ret) { pr_err("%s: Failed to Exit Governor: %s (%d)\n", @@ -2201,9 +2199,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy, if (!ret) goto out; - up_write(&policy->rwsem); __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT); - down_write(&policy->rwsem); } /* new governor failed, so re-start old one */ diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 88a4215..79b87ce 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -100,10 +100,6 @@ struct cpufreq_policy { * - Any routine that will write to the policy structure and/or may take away * the policy altogether (eg. CPU hotplug), will hold this lock in write * mode before doing so. - * - * Additional rules: - * - Lock should not be held across - * __cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT); */ struct rw_semaphore rwsem;
There are no good reasons why policy->rwsem cannot be hold across calls to __cpufreq_governor with CPUFREQ_GOV_POLICY_EXIT event. Remove {up,down}_write across such call sites. This also verify assertion that policy->rwsem is always hold when calling into __cpufreq_governor. Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Juri Lelli <juri.lelli@arm.com> --- drivers/cpufreq/cpufreq.c | 4 ---- include/linux/cpufreq.h | 4 ---- 2 files changed, 8 deletions(-)