arc/Kconfig | 1 + arc/include/asm/cmpxchg.h | 33 ++++++++++++++++++++++++--------- sh/Kconfig | 1 + sh/include/asm/cmpxchg.h | 3 +++ xtensa/Kconfig | 1 + xtensa/include/asm/cmpxchg.h | 2 ++ 6 files changed, 32 insertions(+), 9 deletions(-)
Hello! This series provides an emulation function for one-byte cmpxchg(), and uses it for the remaining architectures not supporting these in hardware and not providing emulation. The emulation is in terms of the fully ordered four-byte cmpxchg() that is supplied by all of these architectures. The emulation has been used in mainline since v6.9 by csky. Once this emulation is in place for all architectures needing it, RCU Tasks will use this capability in place of the current rcu_trc_cmpxchg_need_qs() open-coding of this emulation. 1. xtensa: Emulate one-byte cmpxchg. 2. ARC: Emulate one-byte cmpxchg. 3. sh: Emulate one-byte cmpxchg. Thanx, Paul ------------------------------------------------------------------------ arc/Kconfig | 1 + arc/include/asm/cmpxchg.h | 33 ++++++++++++++++++++++++--------- sh/Kconfig | 1 + sh/include/asm/cmpxchg.h | 3 +++ xtensa/Kconfig | 1 + xtensa/include/asm/cmpxchg.h | 2 ++ 6 files changed, 32 insertions(+), 9 deletions(-)
Hello! This series provides an emulation function for one-byte cmpxchg(), and uses it for the remaining architectures not supporting these in hardware and not providing emulation. The emulation is in terms of the fully ordered four-byte cmpxchg() that is supplied by all of these architectures. The emulation has been used in mainline since v6.9 by csky. Once this emulation is in place for all architectures needing it, RCU Tasks will use this capability in place of the current rcu_trc_cmpxchg_need_qs() open-coding of this emulation. 1. xtensa: Emulate one-byte cmpxchg. 2. ARC: Emulate one-byte cmpxchg. 3. sh: Emulate one-byte cmpxchg. Changes since v1: o Add acked-by tags. Thanx, Paul ------------------------------------------------------------------------ arc/Kconfig | 1 + arc/include/asm/cmpxchg.h | 6 ++++-- sh/Kconfig | 1 + sh/include/asm/cmpxchg.h | 3 +++ xtensa/Kconfig | 1 + xtensa/include/asm/cmpxchg.h | 2 ++ 6 files changed, 12 insertions(+), 2 deletions(-)
Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on xtensa.
[ paulmck: Apply kernel test robot feedback. ]
[ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]
[ Apply Geert Uytterhoeven feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
---
arch/xtensa/Kconfig | 1 +
arch/xtensa/include/asm/cmpxchg.h | 2 ++
2 files changed, 3 insertions(+)
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index f200a4ec044e6..d3db28f2f8110 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -14,6 +14,7 @@ config XTENSA
select ARCH_HAS_DMA_SET_UNCACHED if MMU
select ARCH_HAS_STRNCPY_FROM_USER if !KASAN
select ARCH_HAS_STRNLEN_USER
+ select ARCH_NEED_CMPXCHG_1_EMU
select ARCH_USE_MEMTEST
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
diff --git a/arch/xtensa/include/asm/cmpxchg.h b/arch/xtensa/include/asm/cmpxchg.h
index 675a11ea8de76..95e33a913962d 100644
--- a/arch/xtensa/include/asm/cmpxchg.h
+++ b/arch/xtensa/include/asm/cmpxchg.h
@@ -15,6 +15,7 @@
#include <linux/bits.h>
#include <linux/stringify.h>
+#include <linux/cmpxchg-emu.h>
/*
* cmpxchg
@@ -74,6 +75,7 @@ static __inline__ unsigned long
__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
{
switch (size) {
+ case 1: return cmpxchg_emu_u8(ptr, old, new);
case 4: return __cmpxchg_u32(ptr, old, new);
default: __cmpxchg_called_with_bad_pointer();
return old;
--
2.40.1Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on arc.
[ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]
[ paulmck: Apply feedback from Naresh Kamboju. ]
[ paulmck: Apply kernel test robot feedback. ]
[ paulmck: Apply feedback from Vineet Gupta. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: <linux-snps-arc@lists.infradead.org>
Acked-by: Vineet Gupta <vgupta@kernel.org>
---
arch/arc/Kconfig | 1 +
arch/arc/include/asm/cmpxchg.h | 6 ++++--
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index fd0b0a0d4686a..163608fd49d18 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -13,6 +13,7 @@ config ARC
select ARCH_HAS_SETUP_DMA_OPS
select ARCH_HAS_SYNC_DMA_FOR_CPU
select ARCH_HAS_SYNC_DMA_FOR_DEVICE
+ select ARCH_NEED_CMPXCHG_1_EMU
select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC
select ARCH_32BIT_OFF_T
select BUILDTIME_TABLE_SORT
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index e138fde067dea..58045c8983404 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -8,6 +8,7 @@
#include <linux/build_bug.h>
#include <linux/types.h>
+#include <linux/cmpxchg-emu.h>
#include <asm/barrier.h>
#include <asm/smp.h>
@@ -46,6 +47,9 @@
__typeof__(*(ptr)) _prev_; \
\
switch(sizeof((_p_))) { \
+ case 1: \
+ _prev_ = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)_p_, (uintptr_t)_o_, (uintptr_t)_n_); \
+ break; \
case 4: \
_prev_ = __cmpxchg(_p_, _o_, _n_); \
break; \
@@ -65,8 +69,6 @@
__typeof__(*(ptr)) _prev_; \
unsigned long __flags; \
\
- BUILD_BUG_ON(sizeof(_p_) != 4); \
- \
/* \
* spin lock/unlock provide the needed smp_mb() before/after \
*/ \
--
2.40.1Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on sh.
[ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]
[ paulmck: Apply feedback from Naresh Kamboju. ]
[ Apply Geert Uytterhoeven feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: <linux-sh@vger.kernel.org>
Acked-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
---
arch/sh/Kconfig | 1 +
arch/sh/include/asm/cmpxchg.h | 3 +++
2 files changed, 4 insertions(+)
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 1aa3c4a0c5b27..e9103998cca91 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -14,6 +14,7 @@ config SUPERH
select ARCH_HIBERNATION_POSSIBLE if MMU
select ARCH_MIGHT_HAVE_PC_PARPORT
select ARCH_WANT_IPC_PARSE_VERSION
+ select ARCH_NEED_CMPXCHG_1_EMU
select CPU_NO_EFFICIENT_FFS
select DMA_DECLARE_COHERENT
select GENERIC_ATOMIC64
diff --git a/arch/sh/include/asm/cmpxchg.h b/arch/sh/include/asm/cmpxchg.h
index 5d617b3ef78f7..1e5dc5ccf7bf5 100644
--- a/arch/sh/include/asm/cmpxchg.h
+++ b/arch/sh/include/asm/cmpxchg.h
@@ -9,6 +9,7 @@
#include <linux/compiler.h>
#include <linux/types.h>
+#include <linux/cmpxchg-emu.h>
#if defined(CONFIG_GUSA_RB)
#include <asm/cmpxchg-grb.h>
@@ -56,6 +57,8 @@ static inline unsigned long __cmpxchg(volatile void * ptr, unsigned long old,
unsigned long new, int size)
{
switch (size) {
+ case 1:
+ return cmpxchg_emu_u8(ptr, old, new);
case 4:
return __cmpxchg_u32(ptr, old, new);
}
--
2.40.1© 2016 - 2025 Red Hat, Inc.