diff options
author | John David Anglin <dave.anglin@bell.net> | 2018-08-05 13:30:31 -0400 |
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committer | Helge Deller <deller@gmx.de> | 2018-08-08 22:13:32 +0200 |
commit | fedb8da96355f5f64353625bf96dc69423ad1826 (patch) | |
tree | 36c305623c2a88863801b2f6b5f407af392099eb /arch/parisc/include/asm | |
parent | 66509a276c8c1d19ee3f661a41b418d101c57d29 (diff) |
parisc: Define mb() and add memory barriers to assembler unlock sequences
For years I thought all parisc machines executed loads and stores in
order. However, Jeff Law recently indicated on gcc-patches that this is
not correct. There are various degrees of out-of-order execution all the
way back to the PA7xxx processor series (hit-under-miss). The PA8xxx
series has full out-of-order execution for both integer operations, and
loads and stores.
This is described in the following article:
http://web.archive.org/web/20040214092531/http://www.cpus.hp.com/technical_references/advperf.shtml
For this reason, we need to define mb() and to insert a memory barrier
before the store unlocking spinlocks. This ensures that all memory
accesses are complete prior to unlocking. The ldcw instruction performs
the same function on entry.
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 4.0+
Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'arch/parisc/include/asm')
-rw-r--r-- | arch/parisc/include/asm/barrier.h | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/arch/parisc/include/asm/barrier.h b/arch/parisc/include/asm/barrier.h new file mode 100644 index 000000000000..dbaaca84f27f --- /dev/null +++ b/arch/parisc/include/asm/barrier.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_BARRIER_H +#define __ASM_BARRIER_H + +#ifndef __ASSEMBLY__ + +/* The synchronize caches instruction executes as a nop on systems in + which all memory references are performed in order. */ +#define synchronize_caches() __asm__ __volatile__ ("sync" : : : "memory") + +#if defined(CONFIG_SMP) +#define mb() do { synchronize_caches(); } while (0) +#define rmb() mb() +#define wmb() mb() +#define dma_rmb() mb() +#define dma_wmb() mb() +#else +#define mb() barrier() +#define rmb() barrier() +#define wmb() barrier() +#define dma_rmb() barrier() +#define dma_wmb() barrier() +#endif + +#define __smp_mb() mb() +#define __smp_rmb() mb() +#define __smp_wmb() mb() + +#include <asm-generic/barrier.h> + +#endif /* !__ASSEMBLY__ */ +#endif /* __ASM_BARRIER_H */ |