Re: [PATCH 2/2] ipc/sem.c: Remove duplicated memory barriers.

From	Manfred Spraul <manfred@colorfullife.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] ipc/sem.c: Remove duplicated memory barriers.
Date	2016-07-13 20:40 +0200
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Hi Davidlohr,

On 07/13/2016 06:16 PM, Davidlohr Bueso wrote:
> Manfred, shouldn't this patch be part of patch 1 (as you add the 
> unnecessary barriers there? Iow, can we have a single patch for all this?
>
Two reasons:
- patch 1 is safe for backporting, patch 2 not.
- patch 1 is safe on all architectures, for patch 2 I would like to get 
some review feedback.

e.g. I just found/read 51d7d5205d33 ("powerpc: Add smp_mb() to 
arch_spin_is_locked()"):
For powerpc, a smp_mb() was added into spin_is_locked(), more or less 
for ipc/sem.c.

Patch 1 replaces the spin_is_locked() with smp_load_acquire().
Isn't that the proof that smp_mb() is required?

--
     Manfred

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[PATCH 2/2] ipc/sem.c: Remove duplicated memory barriers. Manfred Spraul <manfred@colorfullife.com> - 2016-07-13 07:10 +0200
  Re: [PATCH 2/2] ipc/sem.c: Remove duplicated memory barriers. Davidlohr Bueso <dave@stgolabs.net> - 2016-07-13 18:20 +0200
    Re: [PATCH 2/2] ipc/sem.c: Remove duplicated memory barriers. Manfred Spraul <manfred@colorfullife.com> - 2016-07-13 20:40 +0200

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