Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it

On Wed, 6 Dec 2006, Al Viro wrote:
> 
> No.  sparc32 doesn't have one, for instance.

Ok. For SMP-safety, it's important that any architecture that can't do 
this needs to _share_ the same spinlock (on SMP only, of course) that it 
uses for the bitops. 

It would be good (but perhaps not as strict a requirement) if the atomic 
counters also use the same lock. But that is probably impossible on 
sparc32 (since it has a per-counter "lock"-like thing, iirc). So doing a 
cmpxchg() on an atomic_t would be a bug.

		Linus
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Follow-Ups:
- Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it
  - From: David Howells <[email protected]>
- Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it
  - From: Matthew Wilcox <[email protected]>

References:
- [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it
  - From: David Howells <[email protected]>
- Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it
  - From: Christoph Lameter <[email protected]>
- Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it
  - From: Linus Torvalds <[email protected]>
- Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it
  - From: Al Viro <[email protected]>

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