On Thu, Mar 7, 2013 at 9:53 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> hotkey_kthread() does try_to_freeze() under hotkey_thread_mutex.
>
> We can simply kill this mutex, hotkey_poll_stop_sync() does not need
> to serialize with hotkey_kthread(). When kthread_stop() returns the
> thread is already dead, it called do_exit()->complete_vfork_done().
>
> Reported-by: Artem Savkov <artem.savkov@xxxxxxxxx>
> Reported-by: Maciej Rutecki <maciej.rutecki@xxxxxxxxx>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
>
Reviewed-by: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
> --- x/drivers/platform/x86/thinkpad_acpi.c
> +++ x/drivers/platform/x86/thinkpad_acpi.c
> @@ -1965,9 +1965,6 @@ struct tp_nvram_state {
> /* kthread for the hotkey poller */
> static struct task_struct *tpacpi_hotkey_task;
>
> -/* Acquired while the poller kthread is running, use to sync start/stop */
> -static struct mutex hotkey_thread_mutex;
> -
> /*
> * Acquire mutex to write poller control variables as an
> * atomic block.
> @@ -2463,8 +2460,6 @@ static int hotkey_kthread(void *data)
> unsigned int poll_freq;
> bool was_frozen;
>
> - mutex_lock(&hotkey_thread_mutex);
> -
> if (tpacpi_lifecycle == TPACPI_LIFE_EXITING)
> goto exit;
>
> @@ -2524,7 +2519,6 @@ static int hotkey_kthread(void *data)
> }
>
> exit:
> - mutex_unlock(&hotkey_thread_mutex);
> return 0;
> }
>
> @@ -2534,9 +2528,6 @@ static void hotkey_poll_stop_sync(void)
> if (tpacpi_hotkey_task) {
> kthread_stop(tpacpi_hotkey_task);
> tpacpi_hotkey_task = NULL;
> - mutex_lock(&hotkey_thread_mutex);
> - /* at this point, the thread did exit */
> - mutex_unlock(&hotkey_thread_mutex);
> }
> }
>
> @@ -3235,7 +3226,6 @@ static int __init hotkey_init(struct ibm
> mutex_init(&hotkey_mutex);
>
> #ifdef CONFIG_THINKPAD_ACPI_HOTKEY_POLL
> - mutex_init(&hotkey_thread_mutex);
> mutex_init(&hotkey_thread_data_mutex);
> #endif
>
>
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