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author | Stephen Boyd <sboyd@codeaurora.org> | 2012-07-20 18:14:38 +0000 |
---|---|---|
committer | Rafael J. Wysocki <rjw@sisk.pl> | 2012-07-20 21:39:25 +0200 |
commit | a9144436271583115a2230db15d0b6ae2c481d3c (patch) | |
tree | 89817e96e6e0f863f5eb1972609650753140ef58 /drivers/cpufreq | |
parent | 53df1ad52545854fc34d336b26f3086b2fb2d6f7 (diff) | |
download | op-kernel-dev-a9144436271583115a2230db15d0b6ae2c481d3c.zip op-kernel-dev-a9144436271583115a2230db15d0b6ae2c481d3c.tar.gz |
cpufreq: Fix sysfs deadlock with concurrent hotplug/frequency switch
Running one program that continuously hotplugs and replugs a cpu
concurrently with another program that continuously writes to the
scaling_setspeed node eventually deadlocks with:
=============================================
[ INFO: possible recursive locking detected ]
3.4.0 #37 Tainted: G W
---------------------------------------------
filemonkey/122 is trying to acquire lock:
(s_active#13){++++.+}, at: [<c01a3d28>] sysfs_remove_dir+0x9c/0xb4
but task is already holding lock:
(s_active#13){++++.+}, at: [<c01a22f0>] sysfs_write_file+0xe8/0x140
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(s_active#13);
lock(s_active#13);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by filemonkey/122:
#0: (&buffer->mutex){+.+.+.}, at: [<c01a2230>] sysfs_write_file+0x28/0x140
#1: (s_active#13){++++.+}, at: [<c01a22f0>] sysfs_write_file+0xe8/0x140
stack backtrace:
[<c0014fcc>] (unwind_backtrace+0x0/0x120) from [<c00ca600>] (validate_chain+0x6f8/0x1054)
[<c00ca600>] (validate_chain+0x6f8/0x1054) from [<c00cb778>] (__lock_acquire+0x81c/0x8d8)
[<c00cb778>] (__lock_acquire+0x81c/0x8d8) from [<c00cb9c0>] (lock_acquire+0x18c/0x1e8)
[<c00cb9c0>] (lock_acquire+0x18c/0x1e8) from [<c01a3ba8>] (sysfs_addrm_finish+0xd0/0x180)
[<c01a3ba8>] (sysfs_addrm_finish+0xd0/0x180) from [<c01a3d28>] (sysfs_remove_dir+0x9c/0xb4)
[<c01a3d28>] (sysfs_remove_dir+0x9c/0xb4) from [<c02d0e5c>] (kobject_del+0x10/0x38)
[<c02d0e5c>] (kobject_del+0x10/0x38) from [<c02d0f74>] (kobject_release+0xf0/0x194)
[<c02d0f74>] (kobject_release+0xf0/0x194) from [<c0565a98>] (cpufreq_cpu_put+0xc/0x24)
[<c0565a98>] (cpufreq_cpu_put+0xc/0x24) from [<c05683f0>] (store+0x6c/0x74)
[<c05683f0>] (store+0x6c/0x74) from [<c01a2314>] (sysfs_write_file+0x10c/0x140)
[<c01a2314>] (sysfs_write_file+0x10c/0x140) from [<c014af44>] (vfs_write+0xb0/0x128)
[<c014af44>] (vfs_write+0xb0/0x128) from [<c014b06c>] (sys_write+0x3c/0x68)
[<c014b06c>] (sys_write+0x3c/0x68) from [<c000e0e0>] (ret_fast_syscall+0x0/0x3c)
This is because store() in cpufreq.c indirectly calls
kobject_get() via cpufreq_cpu_get() and is the last one to call
kobject_put() via cpufreq_cpu_put(). Sysfs code should not call
kobject_get() or kobject_put() directly (see the comment around
sysfs_schedule_callback() for more information).
Fix this deadlock by introducing two new functions:
struct cpufreq_policy *cpufreq_cpu_get_sysfs(unsigned int cpu)
void cpufreq_cpu_put_sysfs(struct cpufreq_policy *data)
which do the same thing as cpufreq_cpu_{get,put}() but don't call
kobject functions.
To easily trigger this deadlock you can insert an msleep() with a
reasonably large value right after the fail label at the bottom
of the store() function in cpufreq.c and then write
scaling_setspeed in one task and offline the cpu in another. The
first task will hang and be detected by the hung task detector.
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r-- | drivers/cpufreq/cpufreq.c | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 7f2f149..fb8a527 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -138,7 +138,7 @@ void disable_cpufreq(void) static LIST_HEAD(cpufreq_governor_list); static DEFINE_MUTEX(cpufreq_governor_mutex); -struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu) +static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs) { struct cpufreq_policy *data; unsigned long flags; @@ -162,7 +162,7 @@ struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu) if (!data) goto err_out_put_module; - if (!kobject_get(&data->kobj)) + if (!sysfs && !kobject_get(&data->kobj)) goto err_out_put_module; spin_unlock_irqrestore(&cpufreq_driver_lock, flags); @@ -175,16 +175,35 @@ err_out_unlock: err_out: return NULL; } + +struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu) +{ + return __cpufreq_cpu_get(cpu, false); +} EXPORT_SYMBOL_GPL(cpufreq_cpu_get); +static struct cpufreq_policy *cpufreq_cpu_get_sysfs(unsigned int cpu) +{ + return __cpufreq_cpu_get(cpu, true); +} -void cpufreq_cpu_put(struct cpufreq_policy *data) +static void __cpufreq_cpu_put(struct cpufreq_policy *data, bool sysfs) { - kobject_put(&data->kobj); + if (!sysfs) + kobject_put(&data->kobj); module_put(cpufreq_driver->owner); } + +void cpufreq_cpu_put(struct cpufreq_policy *data) +{ + __cpufreq_cpu_put(data, false); +} EXPORT_SYMBOL_GPL(cpufreq_cpu_put); +static void cpufreq_cpu_put_sysfs(struct cpufreq_policy *data) +{ + __cpufreq_cpu_put(data, true); +} /********************************************************************* * EXTERNALLY AFFECTING FREQUENCY CHANGES * @@ -617,7 +636,7 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf) struct cpufreq_policy *policy = to_policy(kobj); struct freq_attr *fattr = to_attr(attr); ssize_t ret = -EINVAL; - policy = cpufreq_cpu_get(policy->cpu); + policy = cpufreq_cpu_get_sysfs(policy->cpu); if (!policy) goto no_policy; @@ -631,7 +650,7 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf) unlock_policy_rwsem_read(policy->cpu); fail: - cpufreq_cpu_put(policy); + cpufreq_cpu_put_sysfs(policy); no_policy: return ret; } @@ -642,7 +661,7 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr, struct cpufreq_policy *policy = to_policy(kobj); struct freq_attr *fattr = to_attr(attr); ssize_t ret = -EINVAL; - policy = cpufreq_cpu_get(policy->cpu); + policy = cpufreq_cpu_get_sysfs(policy->cpu); if (!policy) goto no_policy; @@ -656,7 +675,7 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr, unlock_policy_rwsem_write(policy->cpu); fail: - cpufreq_cpu_put(policy); + cpufreq_cpu_put_sysfs(policy); no_policy: return ret; } |