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authorRussell King <rmk+kernel@arm.linux.org.uk>2015-08-12 12:52:16 +0300
committerEduardo Valentin <edubezval@gmail.com>2015-08-15 04:21:41 +0300
commit02373d7c69b4270bbab930f8a81b0721be794347 (patch)
tree4cfe2d1f1621c42bb2ec89eee199fdd1326681eb /drivers/thermal
parentcf736ea6f902c26e03895dc7f5ccbc55cdc68e6e (diff)
downloadlinux-02373d7c69b4270bbab930f8a81b0721be794347.tar.xz
thermal: cpu_cooling: fix lockdep problems in cpu_cooling
A recent change to the cpu_cooling code introduced a AB-BA deadlock scenario between the cpufreq_policy_notifier_list rwsem and the cooling_cpufreq_lock. This is caused by cooling_cpufreq_lock being held before the registration/removal of the notifier block (an operation which takes the rwsem), and the notifier code itself which takes the locks in the reverse order: ====================================================== [ INFO: possible circular locking dependency detected ] 3.18.0+ #1453 Not tainted ------------------------------------------------------- rc.local/770 is trying to acquire lock: (cooling_cpufreq_lock){+.+.+.}, at: [<c04abfc4>] cpufreq_thermal_notifier+0x34/0xfc but task is already holding lock: ((cpufreq_policy_notifier_list).rwsem){++++.+}, at: [<c0042f04>] __blocking_notifier_call_chain+0x34/0x68 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 ((cpufreq_policy_notifier_list).rwsem){++++.+}: [<c06bc3b0>] down_write+0x44/0x9c [<c0043444>] blocking_notifier_chain_register+0x28/0xd8 [<c04ad610>] cpufreq_register_notifier+0x68/0x90 [<c04abe4c>] __cpufreq_cooling_register.part.1+0x120/0x180 [<c04abf44>] __cpufreq_cooling_register+0x98/0xa4 [<c04abf8c>] cpufreq_cooling_register+0x18/0x1c [<bf0046f8>] imx_thermal_probe+0x1c0/0x470 [imx_thermal] [<c037cef8>] platform_drv_probe+0x50/0xac [<c037b710>] driver_probe_device+0x114/0x234 [<c037b8cc>] __driver_attach+0x9c/0xa0 [<c0379d68>] bus_for_each_dev+0x5c/0x90 [<c037b204>] driver_attach+0x24/0x28 [<c037ae7c>] bus_add_driver+0xe0/0x1d8 [<c037c0cc>] driver_register+0x80/0xfc [<c037cd80>] __platform_driver_register+0x50/0x64 [<bf007018>] 0xbf007018 [<c0008a5c>] do_one_initcall+0x88/0x1d8 [<c0095da4>] load_module+0x1768/0x1ef8 [<c0096614>] SyS_init_module+0xe0/0xf4 [<c000ec00>] ret_fast_syscall+0x0/0x48 -> #0 (cooling_cpufreq_lock){+.+.+.}: [<c00619f8>] lock_acquire+0xb0/0x124 [<c06ba3b4>] mutex_lock_nested+0x5c/0x3d8 [<c04abfc4>] cpufreq_thermal_notifier+0x34/0xfc [<c0042bf4>] notifier_call_chain+0x4c/0x8c [<c0042f20>] __blocking_notifier_call_chain+0x50/0x68 [<c0042f58>] blocking_notifier_call_chain+0x20/0x28 [<c04ae62c>] cpufreq_set_policy+0x7c/0x1d0 [<c04af3cc>] store_scaling_governor+0x74/0x9c [<c04ad418>] store+0x90/0xc0 [<c0175384>] sysfs_kf_write+0x54/0x58 [<c01746b4>] kernfs_fop_write+0xdc/0x190 [<c010dcc0>] vfs_write+0xac/0x1b4 [<c010dfec>] SyS_write+0x44/0x90 [<c000ec00>] ret_fast_syscall+0x0/0x48 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((cpufreq_policy_notifier_list).rwsem); lock(cooling_cpufreq_lock); lock((cpufreq_policy_notifier_list).rwsem); lock(cooling_cpufreq_lock); *** DEADLOCK *** 7 locks held by rc.local/770: #0: (sb_writers#6){.+.+.+}, at: [<c010dda0>] vfs_write+0x18c/0x1b4 #1: (&of->mutex){+.+.+.}, at: [<c0174678>] kernfs_fop_write+0xa0/0x190 #2: (s_active#52){.+.+.+}, at: [<c0174680>] kernfs_fop_write+0xa8/0x190 #3: (cpu_hotplug.lock){++++++}, at: [<c0026a60>] get_online_cpus+0x34/0x90 #4: (cpufreq_rwsem){.+.+.+}, at: [<c04ad3e0>] store+0x58/0xc0 #5: (&policy->rwsem){+.+.+.}, at: [<c04ad3f8>] store+0x70/0xc0 #6: ((cpufreq_policy_notifier_list).rwsem){++++.+}, at: [<c0042f04>] __blocking_notifier_call_chain+0x34/0x68 stack backtrace: CPU: 0 PID: 770 Comm: rc.local Not tainted 3.18.0+ #1453 Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) Backtrace: [<c00121c8>] (dump_backtrace) from [<c0012360>] (show_stack+0x18/0x1c) r6:c0b85a80 r5:c0b75630 r4:00000000 r3:00000000 [<c0012348>] (show_stack) from [<c06b6c48>] (dump_stack+0x7c/0x98) [<c06b6bcc>] (dump_stack) from [<c06b42a4>] (print_circular_bug+0x28c/0x2d8) r4:c0b85a80 r3:d0071d40 [<c06b4018>] (print_circular_bug) from [<c00613b0>] (__lock_acquire+0x1acc/0x1bb0) r10:c0b50660 r8:c09e6d80 r7:d0071d40 r6:c11d0f0c r5:00000007 r4:d0072240 [<c005f8e4>] (__lock_acquire) from [<c00619f8>] (lock_acquire+0xb0/0x124) r10:00000000 r9:c04abfc4 r8:00000000 r7:00000000 r6:00000000 r5:c0a06f0c r4:00000000 [<c0061948>] (lock_acquire) from [<c06ba3b4>] (mutex_lock_nested+0x5c/0x3d8) r10:ec853800 r9:c0a06ed4 r8:d0071d40 r7:c0a06ed4 r6:c11d0f0c r5:00000000 r4:c04abfc4 [<c06ba358>] (mutex_lock_nested) from [<c04abfc4>] (cpufreq_thermal_notifier+0x34/0xfc) r10:ec853800 r9:ec85380c r8:d00d7d3c r7:c0a06ed4 r6:d00d7d3c r5:00000000 r4:fffffffe [<c04abf90>] (cpufreq_thermal_notifier) from [<c0042bf4>] (notifier_call_chain+0x4c/0x8c) r7:00000000 r6:00000000 r5:00000000 r4:fffffffe [<c0042ba8>] (notifier_call_chain) from [<c0042f20>] (__blocking_notifier_call_chain+0x50/0x68) r8:c0a072a4 r7:00000000 r6:d00d7d3c r5:ffffffff r4:c0a06fc8 r3:ffffffff [<c0042ed0>] (__blocking_notifier_call_chain) from [<c0042f58>] (blocking_notifier_call_chain+0x20/0x28) r7:ec98b540 r6:c13ebc80 r5:ed76e600 r4:d00d7d3c [<c0042f38>] (blocking_notifier_call_chain) from [<c04ae62c>] (cpufreq_set_policy+0x7c/0x1d0) [<c04ae5b0>] (cpufreq_set_policy) from [<c04af3cc>] (store_scaling_governor+0x74/0x9c) r7:ec98b540 r6:0000000c r5:ec98b540 r4:ed76e600 [<c04af358>] (store_scaling_governor) from [<c04ad418>] (store+0x90/0xc0) r6:0000000c r5:ed76e6d4 r4:ed76e600 [<c04ad388>] (store) from [<c0175384>] (sysfs_kf_write+0x54/0x58) r8:0000000c r7:d00d7f78 r6:ec98b540 r5:0000000c r4:ec853800 r3:0000000c [<c0175330>] (sysfs_kf_write) from [<c01746b4>] (kernfs_fop_write+0xdc/0x190) r6:ec98b540 r5:00000000 r4:00000000 r3:c0175330 [<c01745d8>] (kernfs_fop_write) from [<c010dcc0>] (vfs_write+0xac/0x1b4) r10:0162aa70 r9:d00d6000 r8:0000000c r7:d00d7f78 r6:0162aa70 r5:0000000c r4:eccde500 [<c010dc14>] (vfs_write) from [<c010dfec>] (SyS_write+0x44/0x90) r10:0162aa70 r8:0000000c r7:eccde500 r6:eccde500 r5:00000000 r4:00000000 [<c010dfa8>] (SyS_write) from [<c000ec00>] (ret_fast_syscall+0x0/0x48) r10:00000000 r8:c000edc4 r7:00000004 r6:000216cc r5:0000000c r4:0162aa70 Solve this by moving to finer grained locking - use one mutex to protect the cpufreq_dev_list as a whole, and a separate lock to ensure correct ordering of cpufreq notifier registration and removal. cooling_list_lock is taken within cooling_cpufreq_lock on (un)registration to preserve the behavior of the code, i.e. to atomically add/remove to the list and (un)register the notifier. Fixes: 2dcd851fe4b4 ("thermal: cpu_cooling: Update always cpufreq policy with Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Diffstat (limited to 'drivers/thermal')
-rw-r--r--drivers/thermal/cpu_cooling.c31
1 files changed, 20 insertions, 11 deletions
diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index 6509c61b9648..5ae0524bed19 100644
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -107,6 +107,9 @@ struct cpufreq_cooling_device {
static DEFINE_IDR(cpufreq_idr);
static DEFINE_MUTEX(cooling_cpufreq_lock);
+static unsigned int cpufreq_dev_count;
+
+static DEFINE_MUTEX(cooling_list_lock);
static LIST_HEAD(cpufreq_dev_list);
/**
@@ -185,14 +188,14 @@ unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq)
{
struct cpufreq_cooling_device *cpufreq_dev;
- mutex_lock(&cooling_cpufreq_lock);
+ mutex_lock(&cooling_list_lock);
list_for_each_entry(cpufreq_dev, &cpufreq_dev_list, node) {
if (cpumask_test_cpu(cpu, &cpufreq_dev->allowed_cpus)) {
- mutex_unlock(&cooling_cpufreq_lock);
+ mutex_unlock(&cooling_list_lock);
return get_level(cpufreq_dev, freq);
}
}
- mutex_unlock(&cooling_cpufreq_lock);
+ mutex_unlock(&cooling_list_lock);
pr_err("%s: cpu:%d not part of any cooling device\n", __func__, cpu);
return THERMAL_CSTATE_INVALID;
@@ -221,7 +224,7 @@ static int cpufreq_thermal_notifier(struct notifier_block *nb,
switch (event) {
case CPUFREQ_ADJUST:
- mutex_lock(&cooling_cpufreq_lock);
+ mutex_lock(&cooling_list_lock);
list_for_each_entry(cpufreq_dev, &cpufreq_dev_list, node) {
if (!cpumask_test_cpu(policy->cpu,
&cpufreq_dev->allowed_cpus))
@@ -233,7 +236,7 @@ static int cpufreq_thermal_notifier(struct notifier_block *nb,
cpufreq_verify_within_limits(policy, 0,
max_freq);
}
- mutex_unlock(&cooling_cpufreq_lock);
+ mutex_unlock(&cooling_list_lock);
break;
default:
return NOTIFY_DONE;
@@ -866,12 +869,14 @@ __cpufreq_cooling_register(struct device_node *np,
mutex_lock(&cooling_cpufreq_lock);
+ mutex_lock(&cooling_list_lock);
+ list_add(&cpufreq_dev->node, &cpufreq_dev_list);
+ mutex_unlock(&cooling_list_lock);
+
/* Register the notifier for first cpufreq cooling device */
- if (list_empty(&cpufreq_dev_list))
+ if (!cpufreq_dev_count++)
cpufreq_register_notifier(&thermal_cpufreq_notifier_block,
CPUFREQ_POLICY_NOTIFIER);
- list_add(&cpufreq_dev->node, &cpufreq_dev_list);
-
mutex_unlock(&cooling_cpufreq_lock);
return cool_dev;
@@ -1013,13 +1018,17 @@ void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
return;
cpufreq_dev = cdev->devdata;
- mutex_lock(&cooling_cpufreq_lock);
- list_del(&cpufreq_dev->node);
/* Unregister the notifier for the last cpufreq cooling device */
- if (list_empty(&cpufreq_dev_list))
+ mutex_lock(&cooling_cpufreq_lock);
+ if (!--cpufreq_dev_count)
cpufreq_unregister_notifier(&thermal_cpufreq_notifier_block,
CPUFREQ_POLICY_NOTIFIER);
+
+ mutex_lock(&cooling_list_lock);
+ list_del(&cpufreq_dev->node);
+ mutex_unlock(&cooling_list_lock);
+
mutex_unlock(&cooling_cpufreq_lock);
thermal_cooling_device_unregister(cpufreq_dev->cool_dev);