| Message ID | 11788436.O9o76ZdvQC@kreacher |
|---|---|
| State | New |
| Headers | show |
| Series | cpufreq: Make cpufreq_online() call driver->offline() on errors | expand |
On 21-06-21, 19:26, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > In the CPU removal path the ->offline() callback provided by the > driver is always invoked before ->exit(), Note that exit() doesn't get called if offline() is present in the CPU removal path. We call exit() _only_ when the cpufreq driver gets unregistered. > but in the cpufreq_online() > error path it is not, so ->exit() is somehow expected to know the > context in which it has been called and act accordingly. I agree, it isn't very clear. > That is less than straightforward, so make cpufreq_online() invoke > the driver's ->offline() callback before ->exit() too. > > This only potentially affects intel_pstate at this point. > > Fixes: 91a12e91dc39 ("cpufreq: Allow light-weight tear down and bring up of CPUs") > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > drivers/cpufreq/cpufreq.c | 3 +++ > 1 file changed, 3 insertions(+) > > Index: linux-pm/drivers/cpufreq/cpufreq.c > =================================================================== > --- linux-pm.orig/drivers/cpufreq/cpufreq.c > +++ linux-pm/drivers/cpufreq/cpufreq.c > @@ -1516,6 +1516,9 @@ out_destroy_policy: > up_write(&policy->rwsem); > > out_exit_policy: > + if (cpufreq_driver->offline) > + cpufreq_driver->offline(policy); > + > if (cpufreq_driver->exit) > cpufreq_driver->exit(policy); If we want to go down this path, then we better do more and make it very explicit that ->offline() follows a previous invocation of ->online(). Otherwise, with above we will end up calling ->offline() for two separate states, ->online() failed (i.e. two calls to offline() one after the other here) and other generic failures after ->init() passed. So, better make it clear that online/offline are paired like init/exit. diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 1d1b563cea4b..0ce48dcb2e8a 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1347,14 +1347,11 @@ static int cpufreq_online(unsigned int cpu) } if (!new_policy && cpufreq_driver->online) { - ret = cpufreq_driver->online(policy); - if (ret) { - pr_debug("%s: %d: initialization failed\n", __func__, - __LINE__); - goto out_exit_policy; - } - - /* Recover policy->cpus using related_cpus */ + /* + * We did light-weight tear down earlier, don't need to do heavy + * initialization here. Just recover policy->cpus using + * related_cpus. + */ cpumask_copy(policy->cpus, policy->related_cpus); } else { cpumask_copy(policy->cpus, cpumask_of(cpu)); @@ -1378,6 +1375,13 @@ static int cpufreq_online(unsigned int cpu) cpumask_copy(policy->related_cpus, policy->cpus); } + ret = cpufreq_driver->online(policy); + if (ret) { + pr_debug("%s: %d: %d: ->online() failed\n", __func__, __LINE__, + ret); + goto out_exit_policy; + } + down_write(&policy->rwsem); /* * affected cpus must always be the one, which are online. We aren't @@ -1518,6 +1522,9 @@ static int cpufreq_online(unsigned int cpu) up_write(&policy->rwsem); + if (cpufreq_driver->offline) + cpufreq_driver->offline(policy); + out_exit_policy: if (cpufreq_driver->exit) cpufreq_driver->exit(policy); -- viresh
On Tue, Jun 22, 2021 at 8:20 AM Viresh Kumar <viresh.kumar@linaro.org> wrote: > > On 21-06-21, 19:26, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > In the CPU removal path the ->offline() callback provided by the > > driver is always invoked before ->exit(), > > Note that exit() doesn't get called if offline() is present in the CPU > removal path. We call exit() _only_ when the cpufreq driver gets > unregistered. True, but that doesn't contradict what I said. > > but in the cpufreq_online() > > error path it is not, so ->exit() is somehow expected to know the > > context in which it has been called and act accordingly. > > I agree, it isn't very clear. > > > That is less than straightforward, so make cpufreq_online() invoke > > the driver's ->offline() callback before ->exit() too. > > > > This only potentially affects intel_pstate at this point. > > > > Fixes: 91a12e91dc39 ("cpufreq: Allow light-weight tear down and bring up of CPUs") > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > --- > > drivers/cpufreq/cpufreq.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > Index: linux-pm/drivers/cpufreq/cpufreq.c > > =================================================================== > > --- linux-pm.orig/drivers/cpufreq/cpufreq.c > > +++ linux-pm/drivers/cpufreq/cpufreq.c > > @@ -1516,6 +1516,9 @@ out_destroy_policy: > > up_write(&policy->rwsem); > > > > out_exit_policy: > > + if (cpufreq_driver->offline) > > + cpufreq_driver->offline(policy); > > + > > if (cpufreq_driver->exit) > > cpufreq_driver->exit(policy); > > If we want to go down this path, then we better do more and make it > very explicit that ->offline() follows a previous invocation of > ->online(). > > Otherwise, with above we will end up calling ->offline() for two separate > states, ->online() failed (i.e. two calls to offline() one after the other > here) and other generic failures after ->init() passed. Good point. > So, better make it clear that online/offline are paired like > init/exit. > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index 1d1b563cea4b..0ce48dcb2e8a 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -1347,14 +1347,11 @@ static int cpufreq_online(unsigned int cpu) > } > > if (!new_policy && cpufreq_driver->online) { > - ret = cpufreq_driver->online(policy); > - if (ret) { > - pr_debug("%s: %d: initialization failed\n", __func__, > - __LINE__); > - goto out_exit_policy; > - } > - > - /* Recover policy->cpus using related_cpus */ > + /* > + * We did light-weight tear down earlier, don't need to do heavy > + * initialization here. Just recover policy->cpus using > + * related_cpus. > + */ > cpumask_copy(policy->cpus, policy->related_cpus); > } else { > cpumask_copy(policy->cpus, cpumask_of(cpu)); > @@ -1378,6 +1375,13 @@ static int cpufreq_online(unsigned int cpu) > cpumask_copy(policy->related_cpus, policy->cpus); > } > > + ret = cpufreq_driver->online(policy); But I wouldn't make this change, because that would require reworking ->init() in the driver too. Let's continue assuming that ->init() will do ->online() if successful and so ->offline() is needed after a successful ->init() as well as after a successful ->online(). > + if (ret) { > + pr_debug("%s: %d: %d: ->online() failed\n", __func__, __LINE__, > + ret); > + goto out_exit_policy; > + } > + > down_write(&policy->rwsem); > /* > * affected cpus must always be the one, which are online. We aren't > @@ -1518,6 +1522,9 @@ static int cpufreq_online(unsigned int cpu) > > up_write(&policy->rwsem); > So I think that a new label is needed here to avoid running ->offline() after a failing ->online(). Let me update the patch accordingly. > + if (cpufreq_driver->offline) > + cpufreq_driver->offline(policy); > + > out_exit_policy: > if (cpufreq_driver->exit) > cpufreq_driver->exit(policy);
On 22-06-21, 21:11, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Subject: [PATCH] cpufreq: Make cpufreq_online() call driver->offline() on errors > > In the CPU removal path the ->offline() callback provided by the > driver is always invoked before ->exit(), but in the cpufreq_online() > error path it is not, so ->exit() is expected to somehow know the > context in which it has been called and act accordingly. > > That is less than straightforward, so make cpufreq_online() invoke > the driver's ->offline() callback, if present, on errors before > ->exit() too. > > This only potentially affects intel_pstate. > > Fixes: 91a12e91dc39 ("cpufreq: Allow light-weight tear down and bring up of CPUs") > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > > -> v2: > * Avoid calling ->offline() after a failing ->online(). > * Add a comment regarding the expected state after calling ->init(). > * Edit the changelog a bit. Acked-by: Viresh Kumar <viresh.kumar@linaro.org> -- viresh
Index: linux-pm/drivers/cpufreq/cpufreq.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq.c +++ linux-pm/drivers/cpufreq/cpufreq.c @@ -1516,6 +1516,9 @@ out_destroy_policy: up_write(&policy->rwsem); out_exit_policy: + if (cpufreq_driver->offline) + cpufreq_driver->offline(policy); + if (cpufreq_driver->exit) cpufreq_driver->exit(policy);