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>

diff --git a/arch/parisc/include/asm/barrier.h b/arch/parisc/include/asm/barrier.h
new file mode 100644 (file)
index 0000000..dbaaca8
--- /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 */

diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index e95207c0565eb12308e12d48c45bd5309ae6e2ae..1b4732e201374adc2721ab7141e5ed9b5bf9bd69 100644 (file)
--- 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 22e6374ece4417e76fa91ed196973f6df2356f48..97451e67d35bf8d5c124af7ad88e3546bb33190d 100644 (file)
--- 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 e775f80ae28c5ab8d7fac7456235fa4f415c7215..4886a6db42e98f2b1fc4c58916ee68dfc98df008 100644 (file)
--- 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