Hello,
On Wed, Nov 16, 2011 at 05:25:23PM +0530, Srivatsa S. Bhat wrote:
> v2: Tejun pointed problems with using mutex_lock_interruptible() in a
> while loop, when signals not related to freezing are involved.
> So, replaced it with mutex_trylock().
>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
> ---
>
> include/linux/suspend.h | 14 +++++++++++++-
> 1 files changed, 13 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
> index 57a6924..c2b5aab 100644
> --- a/include/linux/suspend.h
> +++ b/include/linux/suspend.h
> @@ -5,6 +5,7 @@
> #include <linux/notifier.h>
> #include <linux/init.h>
> #include <linux/pm.h>
> +#include <linux/freezer.h>
> #include <linux/mm.h>
> #include <asm/errno.h>
>
> @@ -380,7 +381,18 @@ static inline void unlock_system_sleep(void) {}
>
> static inline void lock_system_sleep(void)
> {
> - mutex_lock(&pm_mutex);
> + /*
> + * We should not use mutex_lock() here because, in case we fail to
> + * acquire the lock, it would put us to sleep in TASK_UNINTERRUPTIBLE
> + * state, which would lead to task freezing failures. As a
> + * consequence, hibernation would fail (even though it had acquired
> + * the 'pm_mutex' lock).
> + *
> + * We should use try_to_freeze() in the while loop so that we don't
> + * cause freezing failures due to busy looping.
> + */
> + while (!mutex_trylock(&pm_mutex))
> + try_to_freeze();
I'm kinda lost. We now always busy-loop if the lock is held by
someone else. I can't see how that is an improvement. If this isn't
an immediate issue, wouldn't it be better to wait for proper solution?
Thank you.
--
tejun
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