Messages in this thread | | | Date | Thu, 24 Mar 2011 17:26:30 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH v2 2/8] block,fs,mm: IO cgroup tracking for buffered write |
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On Wed, 23 Mar 2011 10:21:01 -0700 Justin TerAvest <teravest@google.com> wrote:
> On Tue, Mar 22, 2011 at 9:52 PM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@jp.fujitsu.com> wrote: > > On Tue, 22 Mar 2011 16:08:49 -0700 > > Justin TerAvest <teravest@google.com> wrote: > > > >> +static inline void page_cgroup_set_blkio_id(struct page_cgroup *pc, > >> + unsigned long id) > >> +{ > >> + unsigned long old, new, prev; > >> + > >> + /* pc->flags isn't lock protected, so we must cmpxchg. */ > >> + WARN_ON(id >= (1UL << PAGE_TRACKING_ID_BITS)); > >> + do { > >> + new = old = pc->flags; > >> + new &= (1UL << PAGE_TRACKING_ID_SHIFT) - 1; > >> + new |= (unsigned long)(id << PAGE_TRACKING_ID_SHIFT); > >> + prev = cmpxchg(&pc->flags, old, new); > >> + } while (prev != old); > > > > How to support archs which doesn't have cmpxchg ? > > At least, you need take care of compile error. > > Hi Kame, > > Is there really no generic cmpxchg()? I thought that was what > include/asm-generic/cmpxchg-local.h was for. >
I'm not sure ;) But I myself tend to avoid to use cmpxchg which cannot be used in CONFIG_SMP, sometimes.
Thanks, -Kame
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