From aa0388f2ed937669e9f938da8a65c75ea144ebfd Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Mon, 15 Feb 2021 09:25:55 -0500 Subject: 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 Reviewed-by: Cherry Zhang --- src/runtime/asm_mipsx.s | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'src/runtime/asm_mipsx.s') diff --git a/src/runtime/asm_mipsx.s b/src/runtime/asm_mipsx.s index 341da8e8d7..cf4b1b42cc 100644 --- a/src/runtime/asm_mipsx.s +++ b/src/runtime/asm_mipsx.s @@ -92,12 +92,15 @@ 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|NOFRAME,$0-4 MOVW buf+0(FP), R3 - MOVW gobuf_g(R3), g // make sure g is not nil - JAL runtime·save_g(SB) + MOVW gobuf_g(R3), R4 + MOVW 0(R4), R5 // make sure g != nil + JMP gogo<>(SB) - MOVW 0(g), R2 +TEXT gogo<>(SB),NOSPLIT|NOFRAME,$0 + MOVW R4, g + JAL runtime·save_g(SB) MOVW gobuf_sp(R3), R29 MOVW gobuf_lr(R3), R31 MOVW gobuf_ret(R3), R1 @@ -118,7 +121,6 @@ TEXT runtime·mcall(SB),NOSPLIT|NOFRAME,$0-4 MOVW R29, (g_sched+gobuf_sp)(g) MOVW R31, (g_sched+gobuf_pc)(g) MOVW R0, (g_sched+gobuf_lr)(g) - MOVW g, (g_sched+gobuf_g)(g) // Switch to m->g0 & its stack, call fn. MOVW g, R1 @@ -404,7 +406,6 @@ TEXT gosave_systemstack_switch<>(SB),NOSPLIT|NOFRAME,$0 MOVW R29, (g_sched+gobuf_sp)(g) MOVW R0, (g_sched+gobuf_lr)(g) MOVW R0, (g_sched+gobuf_ret)(g) - MOVW g, (g_sched+gobuf_g)(g) // Assert ctxt is zero. See func save. MOVW (g_sched+gobuf_ctxt)(g), R1 BEQ R1, 2(PC) -- cgit v1.3