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From: Pavel Machek on 28 Apr 2010 01:10
On Tue 2010-04-27 21:31:54, Arve Hj??nnev??g wrote:
> If a suspend_blocker is active, suspend will fail anyway. Since
> try_to_freeze_tasks can take up to 20 seconds to complete or fail, aborting
> as soon as someone blocks suspend (e.g. from an interrupt handler) improves
> the worst case wakeup latency.
>
> On an older kernel where task freezing could fail for processes attached
> to a debugger, this fixed a problem where the device sometimes hung for
> 20 seconds before the screen turned on.
>
> Signed-off-by: Arve Hj??nnev??g <arve(a)android.com>

ack.

> ---
> kernel/power/process.c | 12 ++++++++++--
> 1 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index 71ae290..d8ebd50 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -15,6 +15,7 @@
> #include <linux/syscalls.h>
> #include <linux/freezer.h>
> #include <linux/delay.h>
> +#include <linux/suspend_blocker.h>
>
> /*
> * Timeout for stopping processes
> @@ -38,6 +39,7 @@ static int try_to_freeze_tasks(bool sig_only)
> struct timeval start, end;
> u64 elapsed_csecs64;
> unsigned int elapsed_csecs;
> + bool wakeup = false;
>
> do_gettimeofday(&start);
>
> @@ -63,6 +65,10 @@ static int try_to_freeze_tasks(bool sig_only)
> todo++;
> } while_each_thread(g, p);
> read_unlock(&tasklist_lock);
> + if (todo && suspend_is_blocked()) {
> + wakeup = true;
> + break;
> + }
> if (!todo || time_after(jiffies, end_time))
> break;
>
> @@ -85,13 +91,15 @@ static int try_to_freeze_tasks(bool sig_only)
> * but it cleans up leftover PF_FREEZE requests.
> */
> printk("\n");
> - printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
> + printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
> "(%d tasks refusing to freeze):\n",
> + wakeup ? "aborted" : "failed",
> elapsed_csecs / 100, elapsed_csecs % 100, todo);
> read_lock(&tasklist_lock);
> do_each_thread(g, p) {
> task_lock(p);
> - if (freezing(p) && !freezer_should_skip(p))
> + if (freezing(p) && !freezer_should_skip(p)
> + && elapsed_csecs > 100)
> sched_show_task(p);
> cancel_freezing(p);
> task_unlock(p);

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From: Pavel Machek on 2 May 2010 03:00
Hi!

> If a suspend_blocker is active, suspend will fail anyway. Since
> try_to_freeze_tasks can take up to 20 seconds to complete or fail, aborting
> as soon as someone blocks suspend (e.g. from an interrupt handler) improves
> the worst case wakeup latency.
>
> On an older kernel where task freezing could fail for processes attached
> to a debugger, this fixed a problem where the device sometimes hung for
> 20 seconds before the screen turned on.
>
> Signed-off-by: Arve Hj??nnev??g <arve(a)android.com>

I acked this one before, please preserve such tags.
Pavel

--
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