Re: [PATCH 2/2] locking/rwsem: Disable optimistic spinning for PA-RISC

From: Chris Metcalf
Date: Fri Jun 06 2014 - 13:20:10 EST


On 6/6/2014 1:11 PM, Peter Zijlstra wrote:
The thing is, all these archs are broken beyond this particular problem,
Mikulas Patocka found a number of other spots.

In any case, sure I can exclude more. Although ideally someone goes do
that __atomic sparse thing to flush out all this.

---
Subject: locking, mutex: Disable optimistic spinning on !RMW archs

For some archs a regular store does not play nice with cmpxchg(), the
optimistic spinning code (and various other places not caught by this)
break this assumption and make things go boom.

Until something better is found, disable optimistic spinning for these
archs.

[..]
+config ARCH_NO_ATOMIC_RMW
+ def_bool y
+ depends on PARISC || SPARC32 || METAG_ATOMICITY_LOCK1 || (TILE && !TILEGX) || (ARC && !ARC_HAS_LLSC)

For tile:

Acked-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>

But you should use "TILEPRO" (added in kernel 3.5) instead of "(TILE && !TILEGX)".

--
Chris Metcalf, Tilera Corp.
http://www.tilera.com

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