diff options
Diffstat (limited to 'src/pkg/sync/atomic')
| -rw-r--r-- | src/pkg/sync/atomic/asm_linux_arm.s | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/src/pkg/sync/atomic/asm_linux_arm.s b/src/pkg/sync/atomic/asm_linux_arm.s index 5e7aea292..72f8d746b 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) |