linux/arch/arm64/include/asm/barrier.h
Will Deacon 03e3c2b7ed locking/barriers, arch/arm64: Implement LDXR+WFE based smp_cond_load_acquire()
smp_cond_load_acquire() is used to spin on a variable until some
expression involving that variable becomes true.

On arm64, we can build this using the LDXR and WFE instructions, since
clearing of the exclusive monitor as a result of the variable being
changed by another CPU generates an event, which will wake us up out of WFE.

This patch implements smp_cond_load_acquire() using LDXR and WFE, which
themselves are contained in an internal __cmpwait() function.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: catalin.marinas@arm.com
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1467049434-30451-1-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 09:10:53 +02:00

112 lines
2.9 KiB
C

/*
* Based on arch/arm/include/asm/barrier.h
*
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ASM_BARRIER_H
#define __ASM_BARRIER_H
#ifndef __ASSEMBLY__
#define sev() asm volatile("sev" : : : "memory")
#define wfe() asm volatile("wfe" : : : "memory")
#define wfi() asm volatile("wfi" : : : "memory")
#define isb() asm volatile("isb" : : : "memory")
#define dmb(opt) asm volatile("dmb " #opt : : : "memory")
#define dsb(opt) asm volatile("dsb " #opt : : : "memory")
#define mb() dsb(sy)
#define rmb() dsb(ld)
#define wmb() dsb(st)
#define dma_rmb() dmb(oshld)
#define dma_wmb() dmb(oshst)
#define __smp_mb() dmb(ish)
#define __smp_rmb() dmb(ishld)
#define __smp_wmb() dmb(ishst)
#define __smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
switch (sizeof(*p)) { \
case 1: \
asm volatile ("stlrb %w1, %0" \
: "=Q" (*p) : "r" (v) : "memory"); \
break; \
case 2: \
asm volatile ("stlrh %w1, %0" \
: "=Q" (*p) : "r" (v) : "memory"); \
break; \
case 4: \
asm volatile ("stlr %w1, %0" \
: "=Q" (*p) : "r" (v) : "memory"); \
break; \
case 8: \
asm volatile ("stlr %1, %0" \
: "=Q" (*p) : "r" (v) : "memory"); \
break; \
} \
} while (0)
#define __smp_load_acquire(p) \
({ \
union { typeof(*p) __val; char __c[1]; } __u; \
compiletime_assert_atomic_type(*p); \
switch (sizeof(*p)) { \
case 1: \
asm volatile ("ldarb %w0, %1" \
: "=r" (*(__u8 *)__u.__c) \
: "Q" (*p) : "memory"); \
break; \
case 2: \
asm volatile ("ldarh %w0, %1" \
: "=r" (*(__u16 *)__u.__c) \
: "Q" (*p) : "memory"); \
break; \
case 4: \
asm volatile ("ldar %w0, %1" \
: "=r" (*(__u32 *)__u.__c) \
: "Q" (*p) : "memory"); \
break; \
case 8: \
asm volatile ("ldar %0, %1" \
: "=r" (*(__u64 *)__u.__c) \
: "Q" (*p) : "memory"); \
break; \
} \
__u.__val; \
})
#define smp_cond_load_acquire(ptr, cond_expr) \
({ \
typeof(ptr) __PTR = (ptr); \
typeof(*ptr) VAL; \
for (;;) { \
VAL = smp_load_acquire(__PTR); \
if (cond_expr) \
break; \
__cmpwait_relaxed(__PTR, VAL); \
} \
VAL; \
})
#include <asm-generic/barrier.h>
#endif /* __ASSEMBLY__ */
#endif /* __ASM_BARRIER_H */