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SubjectRe: hung_task checking and sys_sync
On Tue, Jun 12, 2012 at 03:29:12PM -0700, Mandeep Singh Baines wrote:
>
> But the time is not unbounded. You could mask the hung_task_detector for
> this case but then you lose the ability to catch bugs in this code path.
>
> The timeout is configurable via /proc/sys/kernel/hung_task_timeout_secs.
> Can you bump up the value at boot via sysctl.conf?

Maybe, but I'm wondering if these types should just be stopped because Andrew
had complained about them already.

> > Has there been any commit that disable these messages bdi_sched_wait?
> >
>
> No. There is no mechanism to disable hung_task for a specific code path.
> We do skip processes if PF_PROZEN or PF_FROZEN_SKIP is set but that is
> really a different situation where the wait is unbounded.

There is presidence for this type of change,

Author: Mark Lord <kernel@teksavvy.com>
Date: Fri Sep 24 09:51:13 2010 -0400

block: Prevent hang_check firing during long I/O

During long I/O operations, the hang_check timer may fire,
trigger stack dumps that unnecessarily alarm the user.

Eg. hdparm --security-erase NULL /dev/sdb ## can take *hours* to complete

So, if hang_check is armed, we should wake up periodically
to prevent it from triggering. This patch uses a wake-up interval
equal to half the hang_check timer period, which keeps overhead low enough.

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>



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