Re: [PATCH] fix race in mark_mounts_for_expiry()

[Miklos Szeredi <miklos@szeredi.hu>]

> Yes you can. cmpxchg() is atomic. Several archs implement atomic_inc() and co
> with cmpxchg() or similar.
> 
> Something like:
> 
> 	static inline struct namespace *grab_namespace(struct namespace *n)
> 	{
> 		int old = atomic_read(&n->count);
> 
> 		while (old > 0) {
> 			/* attempt to increment the counter */
> 			old = cmpxchg(&n->count, old, old + 1);
> 		}
> 
> 		return old > 0 ? n : NULL;
> 	}
> 

Ahh OK :)

There's still the problem of cmpxchg meddling in the internals of an
atomic_t.  Is that OK?  Will that work on all archs?

Miklos
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