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runtime: reduce syscall when call runtime.clone

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Change-Id: I3ea398fd86aae4c86557dd6fff65d90a6f756890
GitHub-Last-Rev: 4c295388f7
GitHub-Pull-Request: golang/go#40392
Reviewed-on: https://go-review.googlesource.com/c/go/+/244626
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
cui 2020-08-12 17:33:41 +00:00 committed by Ian Lance Taylor
parent 84a62453e5
commit 0941fc3f9f
1 changed files with 21 additions and 13 deletions
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34
src/runtime/sys_linux_amd64.s
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@ -592,13 +592,25 @@ TEXT runtime·clone(SB),NOSPLIT,$0
MOVQ stk+8(FP), SI
MOVQ $0, DX
MOVQ $0, R10
MOVQ $0, R8
// Copy mp, gp, fn off parent stack for use by child.
// Careful: Linux system call clobbers CX and R11.
MOVQ mp+16(FP), R8
MOVQ mp+16(FP), R13
MOVQ gp+24(FP), R9
MOVQ fn+32(FP), R12
CMPQ R13, $0 // m
JEQ nog1
CMPQ R9, $0 // g
JEQ nog1
LEAQ m_tls(R13), R8
#ifdef GOOS_android
// Android stores the TLS offset in runtime·tls_g.
SUBQ runtime·tls_g(SB), R8
#else
ADDQ $8, R8 // ELF wants to use -8(FS)
#endif
ORQ $0x00080000, DI //add flag CLONE_SETTLS(0x00080000) to call clone
nog1:
MOVL $SYS_clone, AX
SYSCALL
@ -612,27 +624,23 @@ TEXT runtime·clone(SB),NOSPLIT,$0
MOVQ SI, SP
// If g or m are nil, skip Go-related setup.
CMPQ R8, $0 // m
JEQ nog
CMPQ R13, $0 // m
JEQ nog2
CMPQ R9, $0 // g
JEQ nog
JEQ nog2
// Initialize m->procid to Linux tid
MOVL $SYS_gettid, AX
SYSCALL
MOVQ AX, m_procid(R8)
// Set FS to point at m->tls.
LEAQ m_tls(R8), DI
CALL runtime·settls(SB)
MOVQ AX, m_procid(R13)
// In child, set up new stack
get_tls(CX)
MOVQ R8, g_m(R9)
MOVQ R13, g_m(R9)
MOVQ R9, g(CX)
CALL runtime·stackcheck(SB)
nog:
nog2:
// Call fn
CALL R12