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| author | Russ Cox <rsc@golang.org> | 2021-02-15 09:25:55 -0500 |
|---|---|---|
| committer | Russ Cox <rsc@golang.org> | 2021-02-19 00:02:23 +0000 |
| commit | aa0388f2ed937669e9f938da8a65c75ea144ebfd (patch) | |
| tree | 511a009cdb84a169c59d4f486a6791616aa7a19d /src/runtime/asm_386.s | |
| parent | 6fe8981620aa61cb43476538f8230231623f9e13 (diff) | |
| download | go-aa0388f2ed937669e9f938da8a65c75ea144ebfd.tar.gz go-aa0388f2ed937669e9f938da8a65c75ea144ebfd.zip | |
runtime: remove unnecessary writes to gp.sched.g
A g's sched.g is set in newproc1:
newg.sched.g = guintptr(unsafe.Pointer(newg))
After that, it never changes. Yet lots of assembly code does
"g.sched.g = g" unnecessarily. Remove all those lines to avoid
confusion about whether it ever changes.
Also, split gogo into two functions, one that does the nil g check
and a second that does the actual switch. This way, if the nil g check
fails, we get a stack trace showing the call stack that led to the failure.
(The SP write would otherwise cause the stack trace to abort.)
Also restore the proper nil g check in a handful of assembly functions.
(There is little point in checking for nil g *after* installing it as the real g.)
Change-Id: I22866b093f901f765de1d074e36eeec10366abfb
Reviewed-on: https://go-review.googlesource.com/c/go/+/292109
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Diffstat (limited to 'src/runtime/asm_386.s')
| -rw-r--r-- | src/runtime/asm_386.s | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/src/runtime/asm_386.s b/src/runtime/asm_386.s index a59054226c..fcf74a03cf 100644 --- a/src/runtime/asm_386.s +++ b/src/runtime/asm_386.s @@ -275,10 +275,13 @@ TEXT runtime·asminit(SB),NOSPLIT,$0-0 // void gogo(Gobuf*) // restore state from Gobuf; longjmp -TEXT runtime·gogo(SB), NOSPLIT, $8-4 +TEXT runtime·gogo(SB), NOSPLIT, $0-4 MOVL buf+0(FP), BX // gobuf MOVL gobuf_g(BX), DX MOVL 0(DX), CX // make sure g != nil + JMP gogo<>(SB) + +TEXT gogo<>(SB), NOSPLIT, $0 get_tls(CX) MOVL DX, g(CX) MOVL gobuf_sp(BX), SP // restore SP @@ -303,7 +306,6 @@ TEXT runtime·mcall(SB), NOSPLIT, $0-4 MOVL BX, (g_sched+gobuf_pc)(AX) LEAL fn+0(FP), BX // caller's SP MOVL BX, (g_sched+gobuf_sp)(AX) - MOVL AX, (g_sched+gobuf_g)(AX) // switch to m->g0 & its stack, call fn MOVL g(DX), BX @@ -432,7 +434,6 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0 // Set g->sched to context in f. MOVL 0(SP), AX // f's PC MOVL AX, (g_sched+gobuf_pc)(SI) - MOVL SI, (g_sched+gobuf_g)(SI) LEAL 4(SP), AX // f's SP MOVL AX, (g_sched+gobuf_sp)(SI) MOVL DX, (g_sched+gobuf_ctxt)(SI) |