[RFC PATCH 00/16] Remove unused arch_*_relax operations from spinlocks

[RFC PATCH 00/16] Remove unused arch_*_relax operations from spinlocks

[Will Deacon]

Hello,

This is an RFC cleanup series removing the unused
arch_{spin,read,write}_relax macros from (nearly) all architectures that
define them. The macros have no users in core code and are typically
synonymous with cpu_relax(), the notable exceptions being PowerPC (where
the thing is still unused) and S390.

S390 does actually use the relax macros internally, as part of the
spinlock implementation, in order to yield the CPU when a virtual CPU
is spinning. For that reason, I've left arch_spin_relax alone there.

Feedback welcome,

Will


Will Deacon (16):
  alpha: locks: remove unused arch_*_relax operations
  arc: locks: remove unused arch_*_relax operations
  ARM: locks: remove unused arch_*_relax operations
  arm64: locks: remove unused arch_*_relax operations
  blackfin: locks: remove unused arch_*_relax operations
  cris: locks: remove unused arch_*_relax operations
  ia64: locks: remove unused arch_*_relax operations
  m32r: locks: remove unused arch_*_relax operations
  metag: locks: remove unused arch_*_relax operations
  mips: locks: remove unused arch_*_relax operations
  hppa: locks: remove unused arch_*_relax operations
  powerpc: locks: remove unused arch_*_relax operations
  s390: locks: remove unused arch_*_relax operations
  sh: locks: remove unused arch_*_relax operations
  sparc: locks: remove unused arch_*_relax operations
  x86: locks: remove unused arch_*_relax operations

 arch/alpha/include/asm/spinlock.h          | 4 ----
 arch/arc/include/asm/spinlock.h            | 4 ----
 arch/arm/include/asm/spinlock.h            | 4 ----
 arch/arm64/include/asm/spinlock.h          | 4 ----
 arch/blackfin/include/asm/spinlock.h       | 4 ----
 arch/cris/include/arch-v32/arch/spinlock.h | 4 ----
 arch/ia64/include/asm/spinlock.h           | 4 ----
 arch/m32r/include/asm/spinlock.h           | 4 ----
 arch/metag/include/asm/spinlock.h          | 4 ----
 arch/metag/include/asm/spinlock_lnkget.h   | 7 -------
 arch/mips/include/asm/spinlock.h           | 4 ----
 arch/parisc/include/asm/spinlock.h         | 4 ----
 arch/powerpc/include/asm/spinlock.h        | 4 ----
 arch/s390/include/asm/spinlock.h           | 3 ---
 arch/sh/include/asm/spinlock.h             | 4 ----
 arch/sparc/include/asm/spinlock_32.h       | 4 ----
 arch/sparc/include/asm/spinlock_64.h       | 4 ----
 arch/x86/include/asm/spinlock.h            | 4 ----
 18 files changed, 74 deletions(-)

-- 
1.8.2.2

[RFC PATCH 01/16] alpha: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for Alpha.

Cc: Matt Turner <mattst88@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/alpha/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/alpha/include/asm/spinlock.h b/arch/alpha/include/asm/spinlock.h
index 3bba21e..37b570d 100644
--- a/arch/alpha/include/asm/spinlock.h
+++ b/arch/alpha/include/asm/spinlock.h
@@ -168,8 +168,4 @@ static inline void arch_write_unlock(arch_rwlock_t * lock)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* _ALPHA_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 02/16] arc: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for Arc.

Cc: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arc/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h
index f158197..fddced5 100644
--- a/arch/arc/include/asm/spinlock.h
+++ b/arch/arc/include/asm/spinlock.h
@@ -137,8 +137,4 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(lock, flags)	arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags)	arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 03/16] ARM: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for ARM.

Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index 6220e9f..46a55a9 100644
--- a/arch/arm/include/asm/spinlock.h
+++ b/arch/arm/include/asm/spinlock.h
@@ -271,8 +271,4 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 04/16] arm64: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for arm64.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index 7065e92..efeadbd 100644
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -195,8 +195,4 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 05/16] blackfin: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for Blackfin.

Cc: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/blackfin/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/blackfin/include/asm/spinlock.h b/arch/blackfin/include/asm/spinlock.h
index 490c7ca..8c58dda 100644
--- a/arch/blackfin/include/asm/spinlock.h
+++ b/arch/blackfin/include/asm/spinlock.h
@@ -96,10 +96,6 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 	__raw_write_unlock_asm(&rw->lock);
 }
 
-#define arch_spin_relax(lock)  	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif
 
 #endif /*  !__BFIN_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 06/16] cris: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for Cris.

Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/cris/include/arch-v32/arch/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/cris/include/arch-v32/arch/spinlock.h b/arch/cris/include/arch-v32/arch/spinlock.h
index f132755..bf94cc6 100644
--- a/arch/cris/include/arch-v32/arch/spinlock.h
+++ b/arch/cris/include/arch-v32/arch/spinlock.h
@@ -124,8 +124,4 @@ static  inline int arch_write_trylock(arch_rwlock_t *rw)
 #define _raw_read_lock_flags(lock, flags) _raw_read_lock(lock)
 #define _raw_write_lock_flags(lock, flags) _raw_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_ARCH_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 07/16] ia64: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for Itanium.

Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/ia64/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/ia64/include/asm/spinlock.h b/arch/ia64/include/asm/spinlock.h
index 54ff557..041f2bc 100644
--- a/arch/ia64/include/asm/spinlock.h
+++ b/arch/ia64/include/asm/spinlock.h
@@ -284,8 +284,4 @@ static inline int arch_read_trylock(arch_rwlock_t *x)
 	return (u32)ia64_cmpxchg4_acq((__u32 *)(x), new.word, old.word) == old.word;
 }
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /*  _ASM_IA64_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 08/16] m32r: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for m32r.

Cc: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/m32r/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/m32r/include/asm/spinlock.h b/arch/m32r/include/asm/spinlock.h
index fa13694..3112249 100644
--- a/arch/m32r/include/asm/spinlock.h
+++ b/arch/m32r/include/asm/spinlock.h
@@ -320,8 +320,4 @@ static inline int arch_write_trylock(arch_rwlock_t *lock)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif	/* _ASM_M32R_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 09/16] metag: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for Metag, including duplicate
definitions of arch_{read,write}_lock_flags.

Cc: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/metag/include/asm/spinlock.h        | 4 ----
 arch/metag/include/asm/spinlock_lnkget.h | 7 -------
 2 files changed, 11 deletions(-)

diff --git a/arch/metag/include/asm/spinlock.h b/arch/metag/include/asm/spinlock.h
index 86a7cf3..15cf4ff 100644
--- a/arch/metag/include/asm/spinlock.h
+++ b/arch/metag/include/asm/spinlock.h
@@ -15,8 +15,4 @@
 #define	arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define	arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_SPINLOCK_H */
diff --git a/arch/metag/include/asm/spinlock_lnkget.h b/arch/metag/include/asm/spinlock_lnkget.h
index ad8436f..73d0345 100644
--- a/arch/metag/include/asm/spinlock_lnkget.h
+++ b/arch/metag/include/asm/spinlock_lnkget.h
@@ -239,11 +239,4 @@ static inline int arch_read_can_lock(arch_rwlock_t *rw)
 	return tmp;
 }
 
-#define	arch_read_lock_flags(lock, flags) arch_read_lock(lock)
-#define	arch_write_lock_flags(lock, flags) arch_write_lock(lock)
-
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_SPINLOCK_LNKGET_H */
-- 
1.8.2.2

[RFC PATCH 10/16] mips: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for MIPS.

Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Daney <david.daney@cavium.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/mips/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h
index 78d201f..7bd850a 100644
--- a/arch/mips/include/asm/spinlock.h
+++ b/arch/mips/include/asm/spinlock.h
@@ -419,8 +419,4 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* _ASM_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 11/16] hppa: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for parisc.

Cc: Helge Deller <deller@gmx.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/parisc/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/parisc/include/asm/spinlock.h b/arch/parisc/include/asm/spinlock.h
index 3516e0b..64f2992 100644
--- a/arch/parisc/include/asm/spinlock.h
+++ b/arch/parisc/include/asm/spinlock.h
@@ -191,8 +191,4 @@ static __inline__ int arch_write_can_lock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 12/16] powerpc: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for PowerPC.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/powerpc/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
index 5b23f91..2d4a841 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -291,9 +291,5 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	__spin_yield(lock)
-#define arch_read_relax(lock)	__rw_yield(lock)
-#define arch_write_relax(lock)	__rw_yield(lock)
-
 #endif /* __KERNEL__ */
 #endif /* __ASM_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 13/16] s390: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for S390. arch_spin_relax is
left alone, since the S390 spinlock internals rely on (and export) this
symbol.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/s390/include/asm/spinlock.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 701fe8c..8b030e2 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -170,7 +170,4 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
 	return _raw_write_trylock_retry(rw);
 }
 
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 14/16] sh: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for SuperH.

Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/sh/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/sh/include/asm/spinlock.h b/arch/sh/include/asm/spinlock.h
index bdc0f3b..a89820d 100644
--- a/arch/sh/include/asm/spinlock.h
+++ b/arch/sh/include/asm/spinlock.h
@@ -219,8 +219,4 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* __ASM_SH_SPINLOCK_H */
-- 
1.8.2.2

[RFC PATCH 15/16] sparc: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for Sparc.

Cc: David Miller <davem@davemloft.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/sparc/include/asm/spinlock_32.h | 4 ----
 arch/sparc/include/asm/spinlock_64.h | 4 ----
 2 files changed, 8 deletions(-)

diff --git a/arch/sparc/include/asm/spinlock_32.h b/arch/sparc/include/asm/spinlock_32.h
index bcc98fc..180c8f3 100644
--- a/arch/sparc/include/asm/spinlock_32.h
+++ b/arch/sparc/include/asm/spinlock_32.h
@@ -188,10 +188,6 @@ static inline int __arch_read_trylock(arch_rwlock_t *rw)
 #define arch_read_lock_flags(rw, flags)   arch_read_lock(rw)
 #define arch_write_lock_flags(rw, flags)  arch_write_lock(rw)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #define arch_read_can_lock(rw) (!((rw)->lock & 0xff))
 #define arch_write_can_lock(rw) (!(rw)->lock)
 
diff --git a/arch/sparc/include/asm/spinlock_64.h b/arch/sparc/include/asm/spinlock_64.h
index 9689176..f3b7a88 100644
--- a/arch/sparc/include/asm/spinlock_64.h
+++ b/arch/sparc/include/asm/spinlock_64.h
@@ -216,10 +216,6 @@ static int inline arch_write_trylock(arch_rwlock_t *lock)
 #define arch_read_can_lock(rw)		(!((rw)->lock & 0x80000000UL))
 #define arch_write_can_lock(rw)	(!(rw)->lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* !(__ASSEMBLY__) */
 
 #endif /* !(__SPARC64_SPINLOCK_H) */
-- 
1.8.2.2

[RFC PATCH 16/16] x86: locks: remove unused arch_*_relax operations

[Will Deacon]

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for x86.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/x86/include/asm/spinlock.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 33692ea..1088d8d 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -229,10 +229,6 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 #undef WRITE_LOCK_SUB
 #undef WRITE_LOCK_CMP
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 /* The {read|write|spin}_lock() on x86 are full memory barriers. */
 static inline void smp_mb__after_lock(void) { }
 #define ARCH_HAS_SMP_MB_AFTER_LOCK
-- 
1.8.2.2

Re: [RFC PATCH 10/16] mips: locks: remove unused arch_*_relax operations

[David Daney]

On 06/21/2013 10:17 AM, Will Deacon wrote:
> The arch_{spin,read,write}_relax macros are not used anywhere in the
> kernel and are typically just aliases for cpu_relax().
>
> This patch removes the unused definitions for MIPS.
>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: David Daney <david.daney@cavium.com>

FWIW: Acked-by: David Daney <david.daney@cavium.com>

> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
>   arch/mips/include/asm/spinlock.h | 4 ----
>   1 file changed, 4 deletions(-)
>
> diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h
> index 78d201f..7bd850a 100644
> --- a/arch/mips/include/asm/spinlock.h
> +++ b/arch/mips/include/asm/spinlock.h
> @@ -419,8 +419,4 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
>   #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
>   #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
>
> -#define arch_spin_relax(lock)	cpu_relax()
> -#define arch_read_relax(lock)	cpu_relax()
> -#define arch_write_relax(lock)	cpu_relax()
> -
>   #endif /* _ASM_SPINLOCK_H */
>

Re: [RFC PATCH 15/16] sparc: locks: remove unused arch_*_relax operations

[David Miller]

From: Will Deacon <will.deacon@arm.com>
Date: Fri, 21 Jun 2013 18:17:36 +0100

> The arch_{spin,read,write}_relax macros are not used anywhere in the
> kernel and are typically just aliases for cpu_relax().
> 
> This patch removes the unused definitions for Sparc.
> 
> Cc: David Miller <davem@davemloft.net>
> Signed-off-by: Will Deacon <will.deacon@arm.com>

Acked-by: David S. Miller <davem@davemloft.net>

Re: [RFC PATCH 16/16] x86: locks: remove unused arch_*_relax operations

[Thomas Gleixner]

On Fri, 21 Jun 2013, Will Deacon wrote:

> The arch_{spin,read,write}_relax macros are not used anywhere in the
> kernel and are typically just aliases for cpu_relax().
> 
> This patch removes the unused definitions for x86.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>

Acked-by: Thomas Gleixner <tglx@linutronix.de>


> ---
>  arch/x86/include/asm/spinlock.h | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
> index 33692ea..1088d8d 100644
> --- a/arch/x86/include/asm/spinlock.h
> +++ b/arch/x86/include/asm/spinlock.h
> @@ -229,10 +229,6 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
>  #undef WRITE_LOCK_SUB
>  #undef WRITE_LOCK_CMP
>  
> -#define arch_spin_relax(lock)	cpu_relax()
> -#define arch_read_relax(lock)	cpu_relax()
> -#define arch_write_relax(lock)	cpu_relax()
> -
>  /* The {read|write|spin}_lock() on x86 are full memory barriers. */
>  static inline void smp_mb__after_lock(void) { }
>  #define ARCH_HAS_SMP_MB_AFTER_LOCK
> -- 
> 1.8.2.2
> 
> 

Re: [RFC PATCH 12/16] powerpc: locks: remove unused arch_*_relax operations

[Benjamin Herrenschmidt]

On Fri, 2013-06-21 at 18:17 +0100, Will Deacon wrote:
> The arch_{spin,read,write}_relax macros are not used anywhere in the
> kernel and are typically just aliases for cpu_relax().
> 
> This patch removes the unused definitions for PowerPC.
> 
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
>  arch/powerpc/include/asm/spinlock.h | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
> index 5b23f91..2d4a841 100644
> --- a/arch/powerpc/include/asm/spinlock.h
> +++ b/arch/powerpc/include/asm/spinlock.h
> @@ -291,9 +291,5 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
>  #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
>  #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
>  
> -#define arch_spin_relax(lock)	__spin_yield(lock)
> -#define arch_read_relax(lock)	__rw_yield(lock)
> -#define arch_write_relax(lock)	__rw_yield(lock)
> -
>  #endif /* __KERNEL__ */
>  #endif /* __ASM_SPINLOCK_H */

Re: [RFC PATCH 02/16] arc: locks: remove unused arch_*_relax operations

[Vineet Gupta]

Hi Will,

On 06/21/2013 10:47 PM, Will Deacon wrote:
> The arch_{spin,read,write}_relax macros are not used anywhere in the
> kernel and are typically just aliases for cpu_relax().
>
> This patch removes the unused definitions for Arc.

For consistency sake, can you please uppercase to ARC in changelog above. Same
goes for arc prefix in patch subject.

>
> Cc: Vineet Gupta <vgupta@synopsys.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>

Acked-by: Vineet Gupta <vgupta@synopsys.com>

Thx,
-Vineet
> ---
>  arch/arc/include/asm/spinlock.h | 4 ----
>  1 file changed, 4 deletions(-)
>
> diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h
> index f158197..fddced5 100644
> --- a/arch/arc/include/asm/spinlock.h
> +++ b/arch/arc/include/asm/spinlock.h
> @@ -137,8 +137,4 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
>  #define arch_read_lock_flags(lock, flags)	arch_read_lock(lock)
>  #define arch_write_lock_flags(lock, flags)	arch_write_lock(lock)
>  
> -#define arch_spin_relax(lock)	cpu_relax()
> -#define arch_read_relax(lock)	cpu_relax()
> -#define arch_write_relax(lock)	cpu_relax()
> -
>  #endif /* __ASM_SPINLOCK_H */

Re: [RFC PATCH 06/16] cris: locks: remove unused arch_*_relax operations

[Jesper Nilsson]

On Fri, Jun 21, 2013 at 07:17:27PM +0200, Will Deacon wrote:
> The arch_{spin,read,write}_relax macros are not used anywhere in the
> kernel and are typically just aliases for cpu_relax().
> 
> This patch removes the unused definitions for Cris.
> 
> Cc: Mikael Starvik <starvik@axis.com>

Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>

> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
>  arch/cris/include/arch-v32/arch/spinlock.h | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/arch/cris/include/arch-v32/arch/spinlock.h b/arch/cris/include/arch-v32/arch/spinlock.h
> index f132755..bf94cc6 100644
> --- a/arch/cris/include/arch-v32/arch/spinlock.h
> +++ b/arch/cris/include/arch-v32/arch/spinlock.h
> @@ -124,8 +124,4 @@ static  inline int arch_write_trylock(arch_rwlock_t *rw)
>  #define _raw_read_lock_flags(lock, flags) _raw_read_lock(lock)
>  #define _raw_write_lock_flags(lock, flags) _raw_write_lock(lock)
>  
> -#define arch_spin_relax(lock)	cpu_relax()
> -#define arch_read_relax(lock)	cpu_relax()
> -#define arch_write_relax(lock)	cpu_relax()
> -
>  #endif /* __ASM_ARCH_SPINLOCK_H */
> -- 
> 1.8.2.2

/^JN - Jesper Nilsson
-- 
               Jesper Nilsson -- jesper.nilsson@axis.com

Re: [RFC PATCH 02/16] arc: locks: remove unused arch_*_relax operations

[Will Deacon]

On Mon, Jun 24, 2013 at 05:12:25AM +0100, Vineet Gupta wrote:
> Hi Will,
> 
> On 06/21/2013 10:47 PM, Will Deacon wrote:
> > The arch_{spin,read,write}_relax macros are not used anywhere in the
> > kernel and are typically just aliases for cpu_relax().
> >
> > This patch removes the unused definitions for Arc.
> 
> For consistency sake, can you please uppercase to ARC in changelog above. Same
> goes for arc prefix in patch subject.

Sure, I'll update the log. I honestly had no idea about the casing and I was
too lazy to look it up :)

Cheers,

Will

Re: [RFC PATCH 09/16] metag: locks: remove unused arch_*_relax operations

[James Hogan]

On 21/06/13 18:17, Will Deacon wrote:
> The arch_{spin,read,write}_relax macros are not used anywhere in the
> kernel and are typically just aliases for cpu_relax().
> 
> This patch removes the unused definitions for Metag, including duplicate
> definitions of arch_{read,write}_lock_flags.
> 
> Cc: James Hogan <james.hogan@imgtec.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>

Acked-by: James Hogan <james.hogan@imgtec.com>

Thanks
James

Re: [RFC PATCH 00/16] Remove unused arch_*_relax operations from spinlocks

[Will Deacon]

On Fri, Jun 21, 2013 at 06:17:21PM +0100, Will Deacon wrote:
> This is an RFC cleanup series removing the unused
> arch_{spin,read,write}_relax macros from (nearly) all architectures that
> define them. The macros have no users in core code and are typically
> synonymous with cpu_relax(), the notable exceptions being PowerPC (where
> the thing is still unused) and S390.

So the `no users in core code' part isn't quite true...

With GENERIC_LOCKBREAK (arm64, ia64, m32r, parisc, powerpc, s390, sh and
sparc), we can actually spit out arch_*_relax calls in kernel/spinlock.c
using some macro concatenation that defeated my grep-fu.

This only makes a difference on powerpc and s390, so we could either:

  (1) conditionally define the relax macros as cpu_relax in spinlock.c (so
      the two guys above can have their special versions)

  (2) Replace the calls with calls to cpu_relax() (although powerpc seems to
      want to know who owns the lock in order to relax)

  (3) Leave the current code alone for architectures that may select
      GENERIC_LOCKBREAK

Any other ideas/preferences?

Will

Re: [RFC PATCH 00/16] Remove unused arch_*_relax operations from spinlocks

[Martin Schwidefsky]

On Mon, 24 Jun 2013 12:58:25 +0100
Will Deacon <will.deacon@arm.com> wrote:

> On Fri, Jun 21, 2013 at 06:17:21PM +0100, Will Deacon wrote:
> > This is an RFC cleanup series removing the unused
> > arch_{spin,read,write}_relax macros from (nearly) all architectures that
> > define them. The macros have no users in core code and are typically
> > synonymous with cpu_relax(), the notable exceptions being PowerPC (where
> > the thing is still unused) and S390.
> 
> So the `no users in core code' part isn't quite true...
> 
> With GENERIC_LOCKBREAK (arm64, ia64, m32r, parisc, powerpc, s390, sh and
> sparc), we can actually spit out arch_*_relax calls in kernel/spinlock.c
> using some macro concatenation that defeated my grep-fu.
> 
> This only makes a difference on powerpc and s390, so we could either:
> 
>   (1) conditionally define the relax macros as cpu_relax in spinlock.c (so
>       the two guys above can have their special versions)
> 
>   (2) Replace the calls with calls to cpu_relax() (although powerpc seems to
>       want to know who owns the lock in order to relax)
> 
>   (3) Leave the current code alone for architectures that may select
>       GENERIC_LOCKBREAK
> 
> Any other ideas/preferences?

Yeah, we never came around to implement arch_read/write_relax. We can remove
the two defines for s390, if we want to add some logic there we can just re-add
an appropriate definition. As powerpc is optimizing their read/write locks
with GENERIC_LOCKBREAK=y we should leave the ability to override the relax
function as it is, no?

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

Re: [RFC PATCH 00/16] Remove unused arch_*_relax operations from spinlocks

[Will Deacon]

On Fri, Jun 28, 2013 at 08:31:03AM +0100, Martin Schwidefsky wrote:
> On Mon, 24 Jun 2013 12:58:25 +0100
> Will Deacon <will.deacon@arm.com> wrote:
> > With GENERIC_LOCKBREAK (arm64, ia64, m32r, parisc, powerpc, s390, sh and
> > sparc), we can actually spit out arch_*_relax calls in kernel/spinlock.c
> > using some macro concatenation that defeated my grep-fu.
> > 
> > This only makes a difference on powerpc and s390, so we could either:
> > 
> >   (1) conditionally define the relax macros as cpu_relax in spinlock.c (so
> >       the two guys above can have their special versions)
> > 
> >   (2) Replace the calls with calls to cpu_relax() (although powerpc seems to
> >       want to know who owns the lock in order to relax)
> > 
> >   (3) Leave the current code alone for architectures that may select
> >       GENERIC_LOCKBREAK
> > 
> > Any other ideas/preferences?
> 
> Yeah, we never came around to implement arch_read/write_relax. We can remove
> the two defines for s390, if we want to add some logic there we can just re-add
> an appropriate definition. As powerpc is optimizing their read/write locks
> with GENERIC_LOCKBREAK=y we should leave the ability to override the relax
> function as it is, no?

Yes, I'll drop the powerpc patch and then add the following patch to the
start of the series for v2.

Cheers,

Will

--->8

From 87707347c9239b647c3b1dd57063eac08fdb1bf4 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon@arm.com>
Date: Mon, 24 Jun 2013 19:06:51 +0100
Subject: [PATCH] locking: add default arch_*_relax definitions for
 GENERIC_LOCKBREAK

When running with GENERIC_LOCKBREAK=y, the locking implementations emit
calls to arch_{read,write,spin}_relax when spinning on a contended lock
in order to allow architectures to favour the CPU owning the lock if
possible.

In reality, everybody apart from PowerPC and S390 just does cpu_relax()
here, so make that the default behaviour and allow it to be overridden
if required.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 kernel/spinlock.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index 5cdd806..4b082b5 100644
--- a/kernel/spinlock.c
+++ b/kernel/spinlock.c
@@ -34,6 +34,20 @@
 #else
 #define raw_read_can_lock(l)	read_can_lock(l)
 #define raw_write_can_lock(l)	write_can_lock(l)
+
+/*
+ * Some architectures can relax in favour of the CPU owning the lock.
+ */
+#ifndef arch_read_relax
+# define arch_read_relax(l)	cpu_relax()
+#endif
+#ifndef arch_write_relax
+# define arch_write_relax(l)	cpu_relax()
+#endif
+#ifndef arch_spin_relax
+# define arch_spin_relax(l)	cpu_relax()
+#endif
+
 /*
  * We build the __lock_function inlines here. They are too large for
  * inlining all over the place, but here is only one user per function
-- 
1.8.2.2