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| author | Russ Cox <rsc@golang.org> | 2011-05-03 01:41:28 -0400 |
|---|---|---|
| committer | Russ Cox <rsc@golang.org> | 2011-05-03 01:41:28 -0400 |
| commit | a7ae73d4e0d6f2131d339bae46d7b1a50050e766 (patch) | |
| tree | c8d0286eac4aeba041dd21bc38cbe0dc1d8261ae | |
| parent | 6a9e2c727917e10d2b4b6d71bb9d3f47043b6c32 (diff) | |
| download | go-a7ae73d4e0d6f2131d339bae46d7b1a50050e766.tar.gz go-a7ae73d4e0d6f2131d339bae46d7b1a50050e766.zip | |
[release-branch.r57] runtime, sync/atomic: fix arm cas
««« CL 4436072 / e280d98747be
runtime, sync/atomic: fix arm cas
Works around bug in kernel implementation on old ARM5 kernels.
Bug was fixed on 26 Nov 2007 (between 2.6.23 and 2.6.24) but
old kernels persist.
Fixes #1750.
R=dfc, golang-dev
CC=golang-dev
https://golang.org/cl/4436072
»»»
TBR=adg
CC=golang-dev
https://golang.org/cl/4452064
| -rw-r--r-- | src/pkg/runtime/linux/arm/sys.s | 15 | ||||
| -rw-r--r-- | src/pkg/sync/atomic/asm_linux_arm.s | 21 |
2 files changed, 32 insertions, 4 deletions
diff --git a/src/pkg/runtime/linux/arm/sys.s b/src/pkg/runtime/linux/arm/sys.s index d866b0e220..2b5365bd86 100644 --- a/src/pkg/runtime/linux/arm/sys.s +++ b/src/pkg/runtime/linux/arm/sys.s @@ -258,11 +258,22 @@ TEXT cas<>(SB),7,$0 TEXT runtime·cas(SB),7,$0 MOVW valptr+0(FP), R2 MOVW old+4(FP), R0 +casagain: MOVW new+8(FP), R1 BL cas<>(SB) - MOVW $0, R0 - MOVW.CS $1, R0 + BCC cascheck + MOVW $1, R0 RET +cascheck: + // Kernel lies; double-check. + MOVW valptr+0(FP), R2 + MOVW old+4(FP), R0 + MOVW 0(R2), R3 + CMP R0, R3 + BEQ casagain + MOVW $0, R0 + RET + TEXT runtime·casp(SB),7,$0 B runtime·cas(SB) diff --git a/src/pkg/sync/atomic/asm_linux_arm.s b/src/pkg/sync/atomic/asm_linux_arm.s index 5e7aea292e..72f8d746bb 100644 --- a/src/pkg/sync/atomic/asm_linux_arm.s +++ b/src/pkg/sync/atomic/asm_linux_arm.s @@ -13,6 +13,12 @@ // LR = return address // The function returns with CS true if the swap happened. // http://lxr.linux.no/linux+v2.6.37.2/arch/arm/kernel/entry-armv.S#L850 +// On older kernels (before 2.6.24) the function can incorrectly +// report a conflict, so we have to double-check the compare ourselves +// and retry if necessary. +// +// http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b49c0f24cf6744a3f4fd09289fe7cade349dead5 +// TEXT cas<>(SB),7,$0 MOVW $0xffff0fc0, PC @@ -23,12 +29,23 @@ TEXT ·CompareAndSwapInt32(SB),7,$0 TEXT ·CompareAndSwapUint32(SB),7,$0 MOVW valptr+0(FP), R2 MOVW old+4(FP), R0 +casagain: MOVW new+8(FP), R1 BL cas<>(SB) - MOVW $0, R0 - MOVW.CS $1, R0 + BCC cascheck + MOVW $1, R0 +casret: MOVW R0, ret+12(FP) RET +cascheck: + // Kernel lies; double-check. + MOVW valptr+0(FP), R2 + MOVW old+4(FP), R0 + MOVW 0(R2), R3 + CMP R0, R3 + BEQ casagain + MOVW $0, R0 + B casret TEXT ·CompareAndSwapUintptr(SB),7,$0 B ·CompareAndSwapUint32(SB) |