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| author |   John David Anglin <dave.anglin@bell.net> | 2018-08-05 13:30:31 -0400 |
|---|---|---|
| committer |   Helge Deller <deller@gmx.de> | 2018-08-08 22:13:32 +0200 |
| commit | fedb8da96355f5f64353625bf96dc69423ad1826 (patch) | |
| tree | 36c305623c2a88863801b2f6b5f407af392099eb /arch/parisc/kernel/entry.S | |
| parent | parisc: Enable CONFIG_MLONGCALLS by default (diff) | |
| download | linux-dev-fedb8da96355f5f64353625bf96dc69423ad1826.tar.xz linux-dev-fedb8da96355f5f64353625bf96dc69423ad1826.zip | |
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/kernel/entry.S')
| -rw-r--r-- | arch/parisc/kernel/entry.S | 2 |
1 files changed, 2 insertions, 0 deletions
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 @@ -482,6 +482,8 @@ .macro tlb_unlock0 spc,tmp #ifdef CONFIG_SMP or,COND(=) %r0,\spc,%r0 + sync + or,COND(=) %r0,\spc,%r0 stw \spc,0(\tmp) #endif .endm |