1. 21 May, 2013 1 commit
    • Viresh Kumar's avatar
      cpufreq: Drop rwsem lock around CPUFREQ_GOV_POLICY_EXIT · 955ef483
      Viresh Kumar authored
      With the rwsem lock around
      __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT), we
      get circular dependency when we call sysfs_remove_group().
      
       ======================================================
       [ INFO: possible circular locking dependency detected ]
       3.9.0-rc7+ #15 Not tainted
       -------------------------------------------------------
       cat/2387 is trying to acquire lock:
        (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c02f6179>] lock_policy_rwsem_read+0x25/0x34
      
       but task is already holding lock:
        (s_active#41){++++.+}, at: [<c00f9bf7>] sysfs_read_file+0x4f/0xcc
      
       which lock already depends on the new lock.
      
       the existing dependency chain (in reverse order) is:
      
      -> #1 (s_active#41){++++.+}:
              [<c0055a79>] lock_acquire+0x61/0xbc
              [<c00fabf1>] sysfs_addrm_finish+0xc1/0x128
              [<c00f9819>] sysfs_hash_and_remove+0x35/0x64
              [<c00fbe6f>] remove_files.isra.0+0x1b/0x24
              [<c00fbea5>] sysfs_remove_group+0x2d/0xa8
              [<c02f9a0b>] cpufreq_governor_interactive+0x13b/0x35c
              [<c02f61df>] __cpufreq_governor+0x2b/0x8c
              [<c02f6579>] __cpufreq_set_policy+0xa9/0xf8
              [<c02f6b75>] store_scaling_governor+0x61/0x100
              [<c02f6f4d>] store+0x39/0x60
              [<c00f9b81>] sysfs_write_file+0xed/0x114
              [<c00b3fd1>] vfs_write+0x65/0xd8
              [<c00b424b>] sys_write+0x2f/0x50
              [<c000cdc1>] ret_fast_syscall+0x1/0x52
      
      -> #0 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}:
              [<c0055253>] __lock_acquire+0xef3/0x13dc
              [<c0055a79>] lock_acquire+0x61/0xbc
              [<c03ee1f5>] down_read+0x25/0x30
              [<c02f6179>] lock_policy_rwsem_read+0x25/0x34
              [<c02f6edd>] show+0x21/0x58
              [<c00f9c0f>] sysfs_read_file+0x67/0xcc
              [<c00b40a7>] vfs_read+0x63/0xd8
              [<c00b41fb>] sys_read+0x2f/0x50
              [<c000cdc1>] ret_fast_syscall+0x1/0x52
      
       other info that might help us debug this:
      
        Possible unsafe locking scenario:
      
              CPU0                    CPU1
              ----                    ----
         lock(s_active#41);
                                      lock(&per_cpu(cpu_policy_rwsem, cpu));
                                      lock(s_active#41);
         lock(&per_cpu(cpu_policy_rwsem, cpu));
      
        *** DEADLOCK ***
      
       2 locks held by cat/2387:
        #0:  (&buffer->mutex){+.+.+.}, at: [<c00f9bcd>] sysfs_read_file+0x25/0xcc
        #1:  (s_active#41){++++.+}, at: [<c00f9bf7>] sysfs_read_file+0x4f/0xcc
      
       stack backtrace:
       [<c0011d55>] (unwind_backtrace+0x1/0x9c) from [<c03e9a09>] (print_circular_bug+0x19d/0x1e8)
       [<c03e9a09>] (print_circular_bug+0x19d/0x1e8) from [<c0055253>] (__lock_acquire+0xef3/0x13dc)
       [<c0055253>] (__lock_acquire+0xef3/0x13dc) from [<c0055a79>] (lock_acquire+0x61/0xbc)
       [<c0055a79>] (lock_acquire+0x61/0xbc) from [<c03ee1f5>] (down_read+0x25/0x30)
       [<c03ee1f5>] (down_read+0x25/0x30) from [<c02f6179>] (lock_policy_rwsem_read+0x25/0x34)
       [<c02f6179>] (lock_policy_rwsem_read+0x25/0x34) from [<c02f6edd>] (show+0x21/0x58)
       [<c02f6edd>] (show+0x21/0x58) from [<c00f9c0f>] (sysfs_read_file+0x67/0xcc)
       [<c00f9c0f>] (sysfs_read_file+0x67/0xcc) from [<c00b40a7>] (vfs_read+0x63/0xd8)
       [<c00b40a7>] (vfs_read+0x63/0xd8) from [<c00b41fb>] (sys_read+0x2f/0x50)
       [<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: default avatarViresh Kumar <viresh.kumar@linaro.org>
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      955ef483
  2. 20 May, 2013 10 commits
  3. 19 May, 2013 3 commits
  4. 18 May, 2013 26 commits