From fedb8da96355f5f64353625bf96dc69423ad1826 Mon Sep 17 00:00:00 2001 From: John David Anglin Date: Sun, 5 Aug 2018 13:30:31 -0400 Subject: parisc: Define mb() and add memory barriers to assembler unlock sequences MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: stable@vger.kernel.org # 4.0+ Signed-off-by: Helge Deller --- arch/parisc/include/asm/barrier.h | 32 ++++++++++++++++++++++++++++++++ arch/parisc/kernel/entry.S | 2 ++ arch/parisc/kernel/pacache.S | 1 + arch/parisc/kernel/syscall.S | 4 ++++ 4 files changed, 39 insertions(+) create mode 100644 arch/parisc/include/asm/barrier.h (limited to 'arch') 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 + +#endif /* !__ASSEMBLY__ */ +#endif /* __ASM_BARRIER_H */ diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index e95207c0565e..1b4732e20137 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -481,6 +481,8 @@ /* Release pa_tlb_lock lock without reloading lock address. */ .macro tlb_unlock0 spc,tmp #ifdef CONFIG_SMP + or,COND(=) %r0,\spc,%r0 + sync or,COND(=) %r0,\spc,%r0 stw \spc,0(\tmp) #endif diff --git a/arch/parisc/kernel/pacache.S b/arch/parisc/kernel/pacache.S index 22e6374ece44..97451e67d35b 100644 --- a/arch/parisc/kernel/pacache.S +++ b/arch/parisc/kernel/pacache.S @@ -353,6 +353,7 @@ ENDPROC_CFI(flush_data_cache_local) .macro tlb_unlock la,flags,tmp #ifdef CONFIG_SMP ldi 1,\tmp + sync stw \tmp,0(\la) mtsm \flags #endif diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index e775f80ae28c..4886a6db42e9 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -633,6 +633,7 @@ cas_action: sub,<> %r28, %r25, %r0 2: stw,ma %r24, 0(%r26) /* Free lock */ + sync stw,ma %r20, 0(%sr2,%r20) #if ENABLE_LWS_DEBUG /* Clear thread register indicator */ @@ -647,6 +648,7 @@ cas_action: 3: /* Error occurred on load or store */ /* Free lock */ + sync stw %r20, 0(%sr2,%r20) #if ENABLE_LWS_DEBUG stw %r0, 4(%sr2,%r20) @@ -848,6 +850,7 @@ cas2_action: cas2_end: /* Free lock */ + sync stw,ma %r20, 0(%sr2,%r20) /* Enable interrupts */ ssm PSW_SM_I, %r0 @@ -858,6 +861,7 @@ cas2_end: 22: /* Error occurred on load or store */ /* Free lock */ + sync stw %r20, 0(%sr2,%r20) ssm PSW_SM_I, %r0 ldo 1(%r0),%r28 -- cgit v1.2.3