linux-kernel - Re: [PATCH] pstore: change mutex locking to spin

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Message-ID: <20110722121302.GB9732@redhat.com>
Date:	Fri, 22 Jul 2011 08:13:02 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Huang Ying <ying.huang@...el.com>
Cc:	"Luck, Tony" <tony.luck@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pstore: change mutex locking to spin_locks

On Fri, Jul 22, 2011 at 08:33:22AM +0800, Huang Ying wrote:
> On 07/22/2011 01:57 AM, Luck, Tony wrote:
> >>> Is it safe to call pstore_mkfile with IRQ disabled?
> >>>
> >>> pstore_mkfile -> d_alloc_name -> d_alloc -> kmem_cache_alloc(, GFP_KERNEL).
> >>
> >> Don't know.  But would that mean we would have to put the pstore_mkfile
> >> on a workqueue then or something similar?
> > 
> > That might be a good idea anyway.  In the "oops" case we'd like the file
> > to appear in the pstore filesystem if the system stayed healthy despite
> > the oops[1]. There isn't any reason why the pstore entry must appear instantly.
> > Delaying the creation would avoid running into problems related to the
> > oops.
> 
> For oops, it may be better to delay writing into something like
> workqueue.  But for panic, I think we should write the record to backend
> (such as ERST) as soon as possible.  So maybe it is better to write to
> backend as soon as possible and delay writing to pstore filesystem.

In the panic case do we care if the pstore fs is mounted (which leads us
to run pstore_mkfile)?

Actually it seems like most of the entry points into pstore_dumper would
not require the fs to create a new file.  I think the exception is an
oops.

Cheers,
Don
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