linux-kernel - [PATCH v2] cpufreq: Make cpufreq_online() call driver->offline() on errors

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Date:   Tue, 22 Jun 2021 21:11:39 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] cpufreq: Make cpufreq_online() call driver->offline() on errors

From: Rafael J. Wysocki <rafael.j.wysocki@...el.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@...el.com>
---

-> v2:
   * Avoid calling ->offline() after a failing ->online().
   * Add a comment regarding the expected state after calling ->init().
   * Edit the changelog a bit.

---
 drivers/cpufreq/cpufreq.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1367,9 +1367,14 @@ static int cpufreq_online(unsigned int c
 			goto out_free_policy;
 		}
 
+		/*
+		 * The initialization has succeeded and the policy is online.
+		 * If there is a problem with its frequency table, take it
+		 * offline and drop it.
+		 */
 		ret = cpufreq_table_validate_and_sort(policy);
 		if (ret)
-			goto out_exit_policy;
+			goto out_offline_policy;
 
 		/* related_cpus should at least include policy->cpus. */
 		cpumask_copy(policy->related_cpus, policy->cpus);
@@ -1515,6 +1520,10 @@ out_destroy_policy:
 
 	up_write(&policy->rwsem);
 
+out_offline_policy:
+	if (cpufreq_driver->offline)
+		cpufreq_driver->offline(policy);
+
 out_exit_policy:
 	if (cpufreq_driver->exit)
 		cpufreq_driver->exit(policy);