linux-kernel - RE: [RFC][PATCH 2/2] efi_pstore: Introducing workqueue updating sysfs entries

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Date:	Fri, 17 Aug 2012 21:15:56 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Mike Waychison <mikew@...gle.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
	"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: RE: [RFC][PATCH 2/2] efi_pstore: Introducing workqueue updating
 sysfs entries


> I'm not a fan of creating a periodic timer that wakes up here to check for an event that should be considered very rare.
> 
> Can this just become scheduled work?  Scheduling work itself is a very lightweight process and should be relatively safe to do from a
> pstore write.

I agree that the periodic timer is heavy a bit.
But I would like to keep a write callback simple as much as possible in panic situation.
For example, I'm concerned that efi_pstore hangs up due to some spin_locks related workqueue like gcwq->lock.

Also,  a situation which this workqueue is needed is just oops case because, system will be down and users can't access to sysfs files
 in other cases, panic, reboot and emergency_restart.

So, Can I call schedule_work in oops case only as follows?

efi_pstore_write()
{
   <write log to NVRAM>

 if (reason != KMSG_DUMP_OOPS)
	return;

schedule_work()

}
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