Hi Yu,

Thanks for review. comments below inline.

quoted

      if (platform_thermal_package_rate_control &&
              platform_thermal_package_rate_control()) {
              /* Rate control is implemented in callback */
              platform_thermal_package_notify(msr_val);

Hum, I have one question, is there a risk here ?

yes, this is main 'goal' of this patch. We need to protect
'platform_thermal_package_notify' because it can be NULL when
'x86_pkg_temp_thermal' module unloading. To achieve this protection
'platform_thermal_lock' introduced.

After graping platform_thermal_lock, we try to get another lock of
worker_pool->lock by :
pkg_temp_thermal_platform_thermal_notify->
schedule_delayed_work_on(cpu,
                                &per_cpu(pkg_temp_thermal_threshold_work, cpu),
                                msecs_to_jiffies(notify_delay_ms));
since schedule_work can be called in many context, and it only use a
spinlock rather than spinlock_irq,  a AB-BA deadlock may happen.

Do you mean spin_lock's in __queue_work ( schedule_delayed_work_on
finally calling this) ?
For my understanding: we should try to re-acquire
platform_thermal_lock to get ABBA deadlock. But according to code we
do not try to do this. Is this correct ?

I think CONFIG_LOCK_DEP might help.

I have built kernel with CONFIG_LOCKDEP enabled. Will stress-test on
my system. FYI, here is grep for platform_thermal_lock:

# egrep platform_thermal_lock /proc/lock_stat
        &(&platform_thermal_lock)->rlock:          9285           9287
          0.16         470.44       35221.94           3.79
21956          23026           0.11         426.52       35563.35
     1.54
        &(&platform_thermal_lock)->rlock           9287
[<ffffffff810439c8>] intel_thermal_interrupt+0xb8/0x230
        &(&platform_thermal_lock)->rlock           9285
[<ffffffff810439c8>] intel_thermal_interrupt+0xb8/0x230
        &(&platform_thermal_lock)->rlock              1
[<ffffffffa0308c77>] enable_thermal_callback+0x19/0x5e
[x86_pkg_temp_thermal]
        &(&platform_thermal_lock)->rlock              1
[<ffffffffa026bc77>] 0xffffffffa026bc77

-- 
Abylay Ospan,
NetUP Inc.
http://www.netup.tv