Re: [PATCH 01/19] freezer: don't get over-anxious while waiting

Pavel Machek
2009-10-01T18:36:52Z

> Freezing isn't exactly the most latency sensitive operation and
> there's no reason to burn cpu cycles and power waiting for it to
> complete. msleep(10) instead of yield(). This should improve
> reliability of emergency hibernation.

i don't see how it improves reliability, but its probably ok.

Well... for hibernation anyway. I can imagine cgroup users where
freeze is so fast that this matters. rjw cc-ed. pavel

> Signed-off-by: Tejun Heo <tj@kernel.org>
> ---
> kernel/power/process.c | 13 +++++++++----
> 1 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index cc2e553..9d26a0a 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -41,7 +41,7 @@ static int try_to_freeze_tasks(bool sig_only)
> do_gettimeofday(&start);
>
> end_time = jiffies + TIMEOUT;
> - do {
> + while (true) {
> todo = 0;
> read_lock(&tasklist_lock);
> do_each_thread(g, p) {
> @@ -62,10 +62,15 @@ static int try_to_freeze_tasks(bool sig_only)
> todo++;
> } while_each_thread(g, p);
> read_unlock(&tasklist_lock);
> - yield(); /* Yield is okay here */
> - if (time_after(jiffies, end_time))
> + if (!todo || time_after(jiffies, end_time))
> break;
> - } while (todo);
> +
> + /*
> + * We need to retry. There's no reason to be
> + * over-anxious about it and waste power.
> + */
> + msleep(10);
> + }
>
> do_gettimeofday(&end);
> elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);

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