On Tue, Jan 05, 2016 at 06:16:48PM +0200, Michael S. Tsirkin wrote:
[snip]

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Another thing is that smp_lwsync() may have a third user(other than
smp_load_acquire() and smp_store_release()):

http://article.gmane.org/gmane.linux.ports.ppc.embedded/89877

I'm OK to change my patch accordingly, but do we really want
smp_lwsync() get involved in this cleanup? If I understand you
correctly, this cleanup focuses on external API like smp_{r,w,}mb(),
while smp_lwsync() is internal to PPC.

Regards,
Boqun

I think you missed the leading ___ :)

What I mean here was smp_lwsync() was originally internal to PPC, but
never mind ;-)

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smp_store_release is external and it needs __smp_lwsync as
defined here.

I can duplicate some code and have smp_lwsync *not* call __smp_lwsync

You mean bringing smp_lwsync() back? because I haven't seen you defining
in asm-generic/barriers.h in previous patches and you just delete it in
this patch.

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but why do this? Still, if you prefer it this way,
please let me know.

I think deleting smp_lwsync() is fine, though I need to change atomic
variants patches on PPC because of it ;-/

Regards,
Boqun

Sorry, I don't understand - why do you have to do anything?
I changed all users of smp_lwsync so they
use __smp_lwsync on SMP and barrier() on !SMP.

This is exactly the current behaviour, I also tested that
generated code does not change at all.

Is there a patch in your tree that conflicts with this?

Because in a patchset which implements atomic relaxed/acquire/release
variants on PPC I use smp_lwsync(), this makes it have another user,
please see this mail:

http://article.gmane.org/gmane.linux.ports.ppc.embedded/89877

in definition of PPC's __atomic_op_release().


But I think removing smp_lwsync() is a good idea and actually I think we
can go further to remove __smp_lwsync() and let __smp_load_acquire and
__smp_store_release call __lwsync() directly, but that is another thing.

Anyway, I will modify my patch.

Regards,
Boqun

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 	WRITE_ONCE(*p, v);						\
 } while (0)
 
-#define smp_load_acquire(p)						\
+#define __smp_load_acquire(p)						\
 ({									\
 	typeof(*p) ___p1 = READ_ONCE(*p);				\
 	compiletime_assert_atomic_type(*p);				\
-	smp_lwsync();							\
+	__smp_lwsync();							\
 	___p1;								\
 })
 
-- 
MST

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