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runtime: make procyieldAsm no longer loop infinitely if passed 0

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Change-Id: I9f01692373623687e09bee54efebaac0ee361f81
Reviewed-on: https://go-review.googlesource.com/c/go/+/712664
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Michael Anthony Knyszek 2025-10-17 20:02:55 +00:00 • committed by Gopher Robot
parent f838faffe2
commit 79ae97fe9b
5 changed files with 11 additions and 7 deletions
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3
src/runtime/asm_386.s
View file

@ -599,10 +599,13 @@ CALLFN(·call1073741824, 1073741824)
TEXT runtime·procyieldAsm(SB),NOSPLIT,$0-0 TEXT runtime·procyieldAsm(SB),NOSPLIT,$0-0
MOVL cycles+0(FP), AX MOVL cycles+0(FP), AX
TESTL AX, AX
JZ done
again: again:
PAUSE PAUSE
SUBL $1, AX SUBL $1, AX
JNZ again JNZ again
done:
RET RET
TEXT ·publicationBarrier(SB),NOSPLIT,$0-0 TEXT ·publicationBarrier(SB),NOSPLIT,$0-0

3
src/runtime/asm_amd64.s
View file

@ -817,10 +817,13 @@ CALLFN(·call1073741824, 1073741824)
TEXT runtime·procyieldAsm(SB),NOSPLIT,$0-0 TEXT runtime·procyieldAsm(SB),NOSPLIT,$0-0
MOVL cycles+0(FP), AX MOVL cycles+0(FP), AX
TESTL AX, AX
JZ done
again: again:
PAUSE PAUSE
SUBL $1, AX SUBL $1, AX
JNZ again JNZ again
done:
RET RET

2
src/runtime/asm_arm64.s
View file

@ -1038,10 +1038,12 @@ aesloop:
TEXT runtime·procyieldAsm(SB),NOSPLIT,$0-0 TEXT runtime·procyieldAsm(SB),NOSPLIT,$0-0
MOVWU cycles+0(FP), R0 MOVWU cycles+0(FP), R0
CBZ R0, done
again: again:
YIELD YIELD
SUBW $1, R0 SUBW $1, R0
CBNZ R0, again CBNZ R0, again
done:
RET RET
// Save state of caller into g->sched, // Save state of caller into g->sched,

3
src/runtime/asm_ppc64x.s
View file

@ -614,6 +614,8 @@ CALLFN(·call1073741824, 1073741824)
TEXT runtime·procyieldAsm(SB),NOSPLIT|NOFRAME,$0-4 TEXT runtime·procyieldAsm(SB),NOSPLIT|NOFRAME,$0-4
MOVW cycles+0(FP), R7 MOVW cycles+0(FP), R7
CMP $0, R7
BEQ done
// POWER does not have a pause/yield instruction equivalent. // POWER does not have a pause/yield instruction equivalent.
// Instead, we can lower the program priority by setting the // Instead, we can lower the program priority by setting the
// Program Priority Register prior to the wait loop and set it // Program Priority Register prior to the wait loop and set it
@ -625,6 +627,7 @@ again:
CMP $0, R7 CMP $0, R7
BNE again BNE again
OR R6, R6, R6 // Set PPR priority back to medium-low OR R6, R6, R6 // Set PPR priority back to medium-low
done:
RET RET
// Save state of caller into g->sched, // Save state of caller into g->sched,

7
src/runtime/stubs.go
View file

@ -283,13 +283,6 @@ func procyield(cycles uint32) {
} }
// procyieldAsm is the assembly implementation of procyield. // procyieldAsm is the assembly implementation of procyield.
//
// It may loop infinitely if called with cycles == 0. Prefer
// procyield, which will compile down to nothing in such cases,
// instead.
//
// FIXME: The implementation really should not loop infinitely if
// the number of cycles is 0.
func procyieldAsm(cycles uint32) func procyieldAsm(cycles uint32)
type neverCallThisFunction struct{} type neverCallThisFunction struct{}