Commit 798282a8 authored Sep 10, 2013 by Rafael J. Wysocki

Revert "cpufreq: make sure frequency transitions are serialized"



Commit 7c30ed53 (cpufreq: make sure frequency transitions are
serialized) attempted to serialize frequency transitions by
adding checks to the CPUFREQ_PRECHANGE and CPUFREQ_POSTCHANGE
notifications.  However, it assumed that the notifications will
always originate from the driver's .target() callback, but they
also can be triggered by cpufreq_out_of_sync() and that leads to
warnings like this on some systems:

 WARNING: CPU: 0 PID: 14543 at drivers/cpufreq/cpufreq.c:317
 __cpufreq_notify_transition+0x238/0x260()
 In middle of another frequency transition

accompanied by a call trace similar to this one:

 [<ffffffff81720daa>] dump_stack+0x46/0x58
 [<ffffffff8106534c>] warn_slowpath_common+0x8c/0xc0
 [<ffffffff815b8560>] ? acpi_cpufreq_target+0x320/0x320
 [<ffffffff81065436>] warn_slowpath_fmt+0x46/0x50
 [<ffffffff815b1ec8>] __cpufreq_notify_transition+0x238/0x260
 [<ffffffff815b33be>] cpufreq_notify_transition+0x3e/0x70
 [<ffffffff815b345d>] cpufreq_out_of_sync+0x6d/0xb0
 [<ffffffff815b370c>] cpufreq_update_policy+0x10c/0x160
 [<ffffffff815b3760>] ? cpufreq_update_policy+0x160/0x160
 [<ffffffff81413813>] cpufreq_set_cur_state+0x8c/0xb5
 [<ffffffff814138df>] processor_set_cur_state+0xa3/0xcf
 [<ffffffff8158e13c>] thermal_cdev_update+0x9c/0xb0
 [<ffffffff8159046a>] step_wise_throttle+0x5a/0x90
 [<ffffffff8158e21f>] handle_thermal_trip+0x4f/0x140
 [<ffffffff8158e377>] thermal_zone_device_update+0x57/0xa0
 [<ffffffff81415b36>] acpi_thermal_check+0x2e/0x30
 [<ffffffff81415ca0>] acpi_thermal_notify+0x40/0xdc
 [<ffffffff813e7dbd>] acpi_device_notify+0x19/0x1b
 [<ffffffff813f8241>] acpi_ev_notify_dispatch+0x41/0x5c
 [<ffffffff813e3fbe>] acpi_os_execute_deferred+0x25/0x32
 [<ffffffff81081060>] process_one_work+0x170/0x4a0
 [<ffffffff81082121>] worker_thread+0x121/0x390
 [<ffffffff81082000>] ? manage_workers.isra.20+0x170/0x170
 [<ffffffff81088fe0>] kthread+0xc0/0xd0
 [<ffffffff81088f20>] ? flush_kthread_worker+0xb0/0xb0
 [<ffffffff8173582c>] ret_from_fork+0x7c/0xb0
 [<ffffffff81088f20>] ? flush_kthread_worker+0xb0/0xb0

For this reason, revert commit 7c30ed53 along with the fix 266c13d7
(cpufreq: Fix serialization of frequency transitions) on top of it
and we will revisit the serialization problem later.

Reported-by: Alessandro Bono <alessandro.bono@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent 5136fa56

drivers/cpufreq/cpufreq.c

+0 −15

Original line number	Diff line number	Diff line
		@@ -280,13 +280,6 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
		switch (state) {

		case CPUFREQ_PRECHANGE:
		if (WARN(policy->transition_ongoing ==
		cpumask_weight(policy->cpus),
		"In middle of another frequency transition\n"))
		return;

		policy->transition_ongoing++;

		/* detect if the driver reported a value as "old frequency"
		* which is not equal to what the cpufreq core thinks is
		* "old frequency".
		@@ -306,12 +299,6 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
		break;

		case CPUFREQ_POSTCHANGE:
		if (WARN(!policy->transition_ongoing,
		"No frequency transition in progress\n"))
		return;

		policy->transition_ongoing--;

		adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);
		pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new,
		(unsigned long)freqs->cpu);
		@@ -1657,8 +1644,6 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,

		if (cpufreq_disabled())
		return -ENODEV;
		if (policy->transition_ongoing)
		return -EBUSY;

		/* Make sure that target_freq is within supported range */
		if (target_freq > policy->max)

include/linux/cpufreq.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -85,7 +85,6 @@ struct cpufreq_policy {
		struct list_head policy_list;
		struct kobject kobj;
		struct completion kobj_unregister;
		int transition_ongoing; /* Tracks transition status */
		};

		/* Only for ACPI */

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