Commit f2519d4d authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

ARC: Emulate one-byte cmpxchg 



Use 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: default avatarPaul 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: default avatarVineet Gupta <vgupta@kernel.org>
parent 8400291e

arch/arc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/arc/include/asm/cmpxchg.h

+4 −2
Original line number Diff line number Diff line
@@ -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	\

	 */								\