From 0a1da095d1cef7c8ac6065da2983565b450566a5 Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Thu, 18 Aug 2022 11:49:39 +0200 Subject: [PATCH] runtime/internal/atomic: remove double-check in kernelcas on linux/arm Older kernels which require the double check of the __kuser_cmpxchg result are no longer supported as of Go 1.18 which requires at least Linux 2.6.32. For #45964 Change-Id: Ic3d6691bf006353ac51b9d43e742d970e3d4e961 Reviewed-on: https://go-review.googlesource.com/c/go/+/424556 Auto-Submit: Tobias Klauser TryBot-Result: Gopher Robot Reviewed-by: Michael Pratt Run-TryBot: Tobias Klauser Reviewed-by: Cherry Mui --- src/runtime/internal/atomic/sys_linux_arm.s | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/src/runtime/internal/atomic/sys_linux_arm.s b/src/runtime/internal/atomic/sys_linux_arm.s index 0cc7fa73d1..9225df8439 100644 --- a/src/runtime/internal/atomic/sys_linux_arm.s +++ b/src/runtime/internal/atomic/sys_linux_arm.s @@ -15,9 +15,6 @@ // 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. // // https://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b49c0f24cf6744a3f4fd09289fe7cade349dead5 // @@ -37,20 +34,13 @@ TEXT kernelcas<>(SB),NOSPLIT,$0 // because we don't know how to traceback through __kuser_cmpxchg MOVW (R2), R0 MOVW old+4(FP), R0 -loop: MOVW new+8(FP), R1 BL cas<>(SB) - BCC check + BCC ret0 MOVW $1, R0 MOVB R0, ret+12(FP) RET -check: - // Kernel lies; double-check. - MOVW ptr+0(FP), R2 - MOVW old+4(FP), R0 - MOVW 0(R2), R3 - CMP R0, R3 - BEQ loop +ret0: MOVW $0, R0 MOVB R0, ret+12(FP) RET -- 2.50.0