Re: [Regression] 2.6.24-git3: Major annoyance during suspend/hibernation on x86-64 (bisected)

On Monday, 28 of January 2008, Dmitry Adamushko wrote:
On 28/01/2008, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
On Sunday, 27 of January 2008, Ingo Molnar wrote:

* Rafael J. Wysocki <rjw@xxxxxxx> wrote:

Hi,

2.6.24-git3 adds a 5 - 10 sec delay to the suspend and hibernation
code paths (probably related to the disabling of nonboot CPUs), which
is !@#$%^&*() annoying.

It's 100% reproducible on my HP nx6325 and bisection idendified the
following commit as the first bad one:

commit 764a9d6fe4b52995c8aba277e3634385699354f4
Author: Steven Rostedt <srostedt@xxxxxxxxxx>
Date: Fri Jan 25 21:08:04 2008 +0100

sched: track highest prio task queued

hm, this patch is a NOP, so it's weird that it has an effect.

Do you have serial logging enabled perhaps? If the following WARN_ON()
triggers:

+ WARN_ON(p->prio < rq->rt.highest_prio);

then perhaps that can cause a 5-10 seconds delay. (that's how much time
it takes to printk a warning on the slowest serial settings)

but if you use suspend, then any such printks would be preserved in the
dmesg, right? If the WARN_ON() triggers, and if you remove it, do things
get faster?

No, this isn't the WARN_ON().

this does have the feel of being scheduling related, but are you
absolutely sure about the precise identity of the patch?

Actually, not quite. That's why I have verified it and found that another
patch is really responsible for the issue, namely:

commit 82a1fcb90287052aabfa235e7ffc693ea003fe69
Author: Ingo Molnar <mingo@xxxxxxx>
Date: Fri Jan 25 21:08:02 2008 +0100

softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks

Reverting this commit (it reverts with some minor modifications) fixes the
problem for me.

What if you use the same kernel that triggers a problem and just disable
this new 'softlockup' functionality:

echo 0 > /proc/sys/kernel/hung_task_timeout_secs

does the problem disapear?

I haven't checked that yet, will do it later today.

Thanks,
Rafael
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