@@ -1732,18 +1732,23 @@ static int __cpufreq_set_policy(struct cpufreq_policy *data,
/* end old governor */
if (data->governor) {
__cpufreq_governor(data, CPUFREQ_GOV_STOP);
+ unlock_policy_rwsem_write(policy->cpu);
__cpufreq_governor(data,
CPUFREQ_GOV_POLICY_EXIT);
+ lock_policy_rwsem_write(policy->cpu);
}
/* start new governor */
data->governor = policy->governor;
if (!__cpufreq_governor(data, CPUFREQ_GOV_POLICY_INIT)) {
- if (!__cpufreq_governor(data, CPUFREQ_GOV_START))
+ if (!__cpufreq_governor(data, CPUFREQ_GOV_START)) {
failed = 0;
- else
+ } else {
+ unlock_policy_rwsem_write(policy->cpu);
__cpufreq_governor(data,
CPUFREQ_GOV_POLICY_EXIT);
+ lock_policy_rwsem_write(policy->cpu);
+ }
}
if (failed) {
With this lock around __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT), we get circular dependency when we call sysfs_remove_group(). [ 195.319079] ====================================================== [ 195.337653] [ INFO: possible circular locking dependency detected ] [ 195.356497] 3.9.0-rc7+ #15 Not tainted [ 195.367758] ------------------------------------------------------- [ 195.386613] cat/2387 is trying to acquire lock: [ 195.400176] (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c02f6179>] lock_policy_rwsem_read+0x25/0x34 [ 195.428920] [ 195.428920] but task is already holding lock: [ 195.446393] (s_active#41){++++.+}, at: [<c00f9bf7>] sysfs_read_file+0x4f/0xcc [ 195.468305] [ 195.468305] which lock already depends on the new lock. [ 195.468305] [ 195.492830] [ 195.492830] the existing dependency chain (in reverse order) is: [ 195.515250] -> #1 (s_active#41){++++.+}: [ 195.527647] [<c0055a79>] lock_acquire+0x61/0xbc [ 195.543129] [<c00fabf1>] sysfs_addrm_finish+0xc1/0x128 [ 195.560362] [<c00f9819>] sysfs_hash_and_remove+0x35/0x64 [ 195.578119] [<c00fbe6f>] remove_files.isra.0+0x1b/0x24 [ 195.595497] [<c00fbea5>] sysfs_remove_group+0x2d/0xa8 [ 195.612469] [<c02f9a0b>] cpufreq_governor_interactive+0x13b/0x35c [ 195.632668] [<c02f61df>] __cpufreq_governor+0x2b/0x8c [ 195.649644] [<c02f6579>] __cpufreq_set_policy+0xa9/0xf8 [ 195.667132] [<c02f6b75>] store_scaling_governor+0x61/0x100 [ 195.685404] [<c02f6f4d>] store+0x39/0x60 [ 195.698989] [<c00f9b81>] sysfs_write_file+0xed/0x114 [ 195.715694] [<c00b3fd1>] vfs_write+0x65/0xd8 [ 195.730320] [<c00b424b>] sys_write+0x2f/0x50 [ 195.744943] [<c000cdc1>] ret_fast_syscall+0x1/0x52 [ 195.761135] -> #0 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}: [ 195.778665] [<c0055253>] __lock_acquire+0xef3/0x13dc [ 195.795371] [<c0055a79>] lock_acquire+0x61/0xbc [ 195.810776] [<c03ee1f5>] down_read+0x25/0x30 [ 195.825398] [<c02f6179>] lock_policy_rwsem_read+0x25/0x34 [ 195.843410] [<c02f6edd>] show+0x21/0x58 [ 195.856731] [<c00f9c0f>] sysfs_read_file+0x67/0xcc [ 195.872919] [<c00b40a7>] vfs_read+0x63/0xd8 [ 195.887282] [<c00b41fb>] sys_read+0x2f/0x50 [ 195.901645] [<c000cdc1>] ret_fast_syscall+0x1/0x52 [ 195.917863] [ 195.917863] other info that might help us debug this: [ 195.917863] [ 195.941853] Possible unsafe locking scenario: [ 195.941853] [ 195.959586] CPU0 CPU1 [ 195.973149] ---- ---- [ 195.986712] lock(s_active#41); [ 195.996407] lock(&per_cpu(cpu_policy_rwsem, cpu)); [ 196.018912] lock(s_active#41); [ 196.036161] lock(&per_cpu(cpu_policy_rwsem, cpu)); [ 196.051051] [ 196.051051] *** DEADLOCK *** [ 196.051051] [ 196.068792] 2 locks held by cat/2387: [ 196.079750] #0: (&buffer->mutex){+.+.+.}, at: [<c00f9bcd>] sysfs_read_file+0x25/0xcc [ 196.103546] #1: (s_active#41){++++.+}, at: [<c00f9bf7>] sysfs_read_file+0x4f/0xcc [ 196.126577] [ 196.126577] stack backtrace: [ 196.139644] [<c0011d55>] (unwind_backtrace+0x1/0x9c) from [<c03e9a09>] (print_circular_bug+0x19d/0x1e8) [ 196.167857] [<c03e9a09>] (print_circular_bug+0x19d/0x1e8) from [<c0055253>] (__lock_acquire+0xef3/0x13dc) [ 196.196542] [<c0055253>] (__lock_acquire+0xef3/0x13dc) from [<c0055a79>] (lock_acquire+0x61/0xbc) [ 196.223139] [<c0055a79>] (lock_acquire+0x61/0xbc) from [<c03ee1f5>] (down_read+0x25/0x30) [ 196.247722] [<c03ee1f5>] (down_read+0x25/0x30) from [<c02f6179>] (lock_policy_rwsem_read+0x25/0x34) [ 196.274905] [<c02f6179>] (lock_policy_rwsem_read+0x25/0x34) from [<c02f6edd>] (show+0x21/0x58) [ 196.300724] [<c02f6edd>] (show+0x21/0x58) from [<c00f9c0f>] (sysfs_read_file+0x67/0xcc) [ 196.324719] [<c00f9c0f>] (sysfs_read_file+0x67/0xcc) from [<c00b40a7>] (vfs_read+0x63/0xd8) [ 196.349756] [<c00b40a7>] (vfs_read+0x63/0xd8) from [<c00b41fb>] (sys_read+0x2f/0x50) [ 196.372970] [<c00b41fb>] (sys_read+0x2f/0x50) from [<c000cdc1>] (ret_fast_syscall+0x1/0x52) This lock isn't required while calling __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT). Remove it. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- drivers/cpufreq/cpufreq.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)