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[PATCH 0/3] atomic_or() related changes

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  [PATCH 0/3] atomic_or() related changes Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-07-09 10:20 +0200
    [PATCH 3/3] ARC: provide atomic_or() and define ARCH_HAS_ATOMIC_OR Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-07-09 10:20 +0200
    [PATCH 1/3] asm-generic/atomic.h: ARCH_HAS_ATOMIC_OR -> CONFIG_ARCH_HAS_ATOMIC_OR Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-07-09 10:20 +0200
    Re: [PATCH 0/3] atomic_or() related changes Peter Zijlstra <peterz@infradead.org> - 2015-07-09 14:40 +0200
      Re: [PATCH 0/3] atomic_or() related changes Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-07-09 15:10 +0200

#1180528 — [PATCH 0/3] atomic_or() related changes

Hi,

This started off as an effort to convert a cmpxchg based loop in arc/kernel/smp.c
to an API which is more LLOCK/SCOND friendly.

e.g.
        do {
                new = old = ACCESS_ONCE(*ipi_data_ptr);
                new |= 1U << msg;
        } while (cmpxchg(ipi_data_ptr, old, new) != old);

The generated code is horrible. There are 2 useless branches here and a
LD/LLOCK to same address all inside a loop.

8015cefc:	ld_s       r2,[r3,0]
8015cefe:	or         r5,r2,r1
8015cf02:	llock      r4,[r3]
8015cf06:	brne       r4,r2,8015cf12
8015cf0a:	scond      r5,[r3]
8015cf0e:	bnz        8015cf02
8015cf12:	brne       r2,r4,8015cefc

An atomic_or() kind of API is better suited to generate something like below

8015cf02:	llock      r4,[r3]
8015cf06:	or         r5,r2,r1
8015cf0a:	scond      r5,[r3]
8015cf0e:	bnz        8015cf02

Although this doesn't work for the specific instance I wanted to fix as
ipi_data_ptr is not atomic_t, I did run into a few things which could be
improved, hence this series.

Compile tested on ARC, ARM, x86.

I do have some concern about mixing long and int on 64 bit arch, which I've
captured inline in patch 2/3. It is most likely a lack of understand on my
part, but worth asking..

Thx,
-Vineet

Vineet Gupta (3):
  asm-generic/atomic.h: ARCH_HAS_ATOMIC_OR -> CONFIG_ARCH_HAS_ATOMIC_OR
  brcmfmac: dhd_sdio.c: use existing atomic_or primitive
  ARC: provide atomic_or() and define ARCH_HAS_ATOMIC_OR

 arch/arc/include/asm/atomic.h                  |  9 +++++++++
 drivers/net/wireless/brcm80211/brcmfmac/sdio.c | 13 ++-----------
 include/asm-generic/atomic.h                   |  2 +-
 include/linux/atomic.h                         |  4 ++--
 4 files changed, 14 insertions(+), 14 deletions(-)

-- 
1.9.1

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#1180532 — [PATCH 3/3] ARC: provide atomic_or() and define ARCH_HAS_ATOMIC_OR

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 arch/arc/include/asm/atomic.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 03484cb4d16d..fab27dbc562b 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -141,10 +141,19 @@ static inline int atomic_##op##_return(int i, atomic_t *v)		\
 	ATOMIC_OP(op, c_op, asm_op)					\
 	ATOMIC_OP_RETURN(op, c_op, asm_op)
 
+/* atomic_add(), atomic_add_return() */
 ATOMIC_OPS(add, +=, add)
+
+/* atomic_sub(), atomic_sub_return() */
 ATOMIC_OPS(sub, -=, sub)
+
+/* atomic_and() */
 ATOMIC_OP(and, &=, and)
 
+#define ARCH_HAS_ATOMIC_OR
+/* atomic_or() */
+ATOMIC_OP(or, |=, or)
+
 #define atomic_clear_mask(mask, v) atomic_and(~(mask), (v))
 
 #undef ATOMIC_OPS
-- 
1.9.1

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#1180537 — [PATCH 1/3] asm-generic/atomic.h: ARCH_HAS_ATOMIC_OR -> CONFIG_ARCH_HAS_ATOMIC_OR

Since this is not backed by a Kconfig option, remove CONFIG_ prefix

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 include/asm-generic/atomic.h | 2 +-
 include/linux/atomic.h       | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
index 1973ad2b13f4..1a1cdab6e702 100644
--- a/include/asm-generic/atomic.h
+++ b/include/asm-generic/atomic.h
@@ -104,7 +104,7 @@ ATOMIC_OP(and, &)
 #endif
 
 #ifndef atomic_set_mask
-#define CONFIG_ARCH_HAS_ATOMIC_OR
+#define ARCH_HAS_ATOMIC_OR
 ATOMIC_OP(or, |)
 #define atomic_set_mask(i, v)	atomic_or((i), (v))
 #endif
diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 5b08a8540ecf..195881eec33e 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -111,7 +111,7 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 }
 #endif
 
-#ifndef CONFIG_ARCH_HAS_ATOMIC_OR
+#ifndef ARCH_HAS_ATOMIC_OR
 static inline void atomic_or(int i, atomic_t *v)
 {
 	int old;
@@ -122,7 +122,7 @@ static inline void atomic_or(int i, atomic_t *v)
 		new = old | i;
 	} while (atomic_cmpxchg(v, old, new) != old);
 }
-#endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR */
+#endif /* #ifndef ARCH_HAS_ATOMIC_OR */
 
 #include <asm-generic/atomic-long.h>
 #ifdef CONFIG_GENERIC_ATOMIC64
-- 
1.9.1

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#1180684

I see what you did there.. gimme a few more hours, I'll finish what I
have and stuff it through the build bot.

I've just not managed to finish tile, but did do frv this time.
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#1180740

On Thursday 09 July 2015 06:01 PM, Peter Zijlstra wrote:
> I've just not managed to finish tile, but did do frv this time.

Not sure what you mean - are you also doing a similar series which extends
atomic_or to other arches too which will probably we simpler now given ur earlier
macro-fication of this code !

-vineet
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