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List:       linux-kernel
Subject:    [PATCH] 2.6 PPC64: lockfix for rtas error log (third-times-a-charm?)
From:       linas () austin ! ibm ! com
Date:       2004-06-30 20:31:20
Message-ID: 20040630153120.W21634 () forte ! austin ! ibm ! com
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On Wed, Jun 30, 2004 at 01:47:29PM -0500, Benjamin Herrenschmidt wrote:
> 
> > Well, the problem was that there is no lock that is protecting the
> > use of the single, global buffer.  Adding yet another lock is bad;
> > it makes hunting for deadlocks that much more tedious and difficult;
> > already, finding deadlocks is error-prone, and subject to bit-rot as
> > future hackers update the code.  So instead, the problem can be easily
> > avoided by not using a global buffer.  The code below mallocs/frees.
> > Its not perf-critcal, so I don't mind malloc overhead.  Would this
> > work for you?  Patch attached below.
> 
> I prefer that, but couldn't we move the kmalloc outside of the spinlock
> and so use GFP_KERNEL instead ?

OK,

Upon closer analysis of the code, I see that log_rtas_error() 
was incorrectly named, and was being used incorrectly.  The 
solution is to get rid of it entirely; see patch below. So:

-- In one case kmalloc must be GFP_ATOMIC because rtas_call()
   can happen in any context, incl. irqs.
-- In the other case, I turned it into GFP_KENREL, at the cost
   of doing a needless malloc/free in the vast majority of 
   cases where there is no error.  Small price, as I beleive
   that this routine is very rarely called.

Patch below, 
Signed-off-by: Linas Vepstas <linas@linas.org>

--linas

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