linux-kernel - Re: [PATCH 0/7] V3 of the async function call patches

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Message-ID: <20090107172102.47f778d4@infradead.org>
Date:	Wed, 7 Jan 2009 17:21:02 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/7] V3 of the async function call patches

On Wed, 7 Jan 2009 16:17:24 -0800 (PST)
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> 
> 
> On Wed, 7 Jan 2009, Arjan van de Ven wrote:
> >
> > version 3 of the async function call patches
> > 
> > * Dropped the ACPI part; it broke i surprising ways; needs a rethink
> >   (working with Len and co on that)
> > * Included asynchronous delete()
> 
> Ok, I pulled this, because I really do want the boot speedups and the 
> previous version missed the last merge window, but after booting it,
> I started to worry:
> 
> My dmesg shows:
> 
>  [    2.264955] sd 5:0:0:0: [sdb] Write cache: enabled, read cache:
> enabled, doesn't support DPO or FUA [    2.264958]  sdb:<6>Freeing
> unused kernel memory: 408k freed
> 
> Ouch. How come that "Freeing unused kernel memory" got done in the
> middle of the sdb partition thing?
> 
> There's a async_synchronize_full() there before the free_initmem(),
> but I'm worrying that it just isn't working. Hmm? What am I missing?
> 

ok this part looks funny but it's not really (and it's safe I think).

The async sata thing launches another async thing (the scsi partition
scan).
The synchronize_full() waits for the sata to complete, but doesn't wait
for things that the sata async schedules after the wait started.

is this a problem? not right now, but it means we have a rule that if
an async item schedules another async item, the second one cannot be
__init. (which is ok right now.. scsi already had some of this async
anyway).

I could make the async_full() be more strict if that makes you feel
better, but for this specific purpose it would be over-synchronizing.


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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