Messages in this thread Patch in this message |  | | Date | Thu, 17 Jan 2013 21:51:09 +0000 | From | Christoph Lameter <> | Subject | Re: [RFC][PATCH] slub: Check for page NULL before doing the node_match check |
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On Thu, 17 Jan 2013, Steven Rostedt wrote:
> > c->tid = next_tid(c->tid); > > - c->page = NULL; > > c->freelist = NULL; > > + c->page = NULL; > > I'm assuming that this is to deal with the same CPU being able to touch > the code? > > If so, it requires "barrier()". If this can affect other CPUs, then we > need a smp_wmb() here, and smp_rmb() where it matters.
This is dealing with the same cpu being interrupted. Some of these segments are in interrupt disable sections so they are not affected.
The above is a section where interrupts are enabled so it needs the barriers.
> > @@ -2227,8 +2227,8 @@ redo: > > if (unlikely(!node_match(page, node))) { > > stat(s, ALLOC_NODE_MISMATCH); > > deactivate_slab(s, page, c->freelist); > > - c->page = NULL; > > c->freelist = NULL; > > + c->page = NULL; > > goto new_slab; > > } > >
Interrupts are disabled so we do not need to change anything here.
> > @@ -2239,8 +2239,8 @@ redo: > > */ > > if (unlikely(!pfmemalloc_match(page, gfpflags))) { > > deactivate_slab(s, page, c->freelist); > > - c->page = NULL; > > c->freelist = NULL; > > + c->page = NULL; > > goto new_slab; > > } > >
Ditto which leaves us with:
Index: linux/mm/slub.c =================================================================== --- linux.orig/mm/slub.c 2013-01-17 15:49:57.417491975 -0600 +++ linux/mm/slub.c 2013-01-17 15:50:49.010287150 -0600 @@ -1993,8 +1993,9 @@ static inline void flush_slab(struct kme deactivate_slab(s, c->page, c->freelist);
c->tid = next_tid(c->tid); - c->page = NULL; c->freelist = NULL; + barrier(); + c->page = NULL; }
/*
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