runtime: make runtime·usleep and runtime·osyield callable from cgo callback

runtime·usleep and runtime·osyield fall back to calling an
assembly wrapper for the libc functions in the absence of a m,
so they can be called in cgo callback context.

LGTM=rsc
R=minux.ma, rsc
CC=dave, golang-codereviews
https://golang.org/cl/102620044

diff --git a/src/pkg/runtime/os_solaris.c b/src/pkg/runtime/os_solaris.c
index 4ef17f90212d8cc7ffeb532a19995ad13b390fc0..fe218cdb81feaae3771a0057e38a3697ddf4d8d5 100644 (file)
--- a/src/pkg/runtime/os_solaris.c
+++ b/src/pkg/runtime/os_solaris.c
@@ -568,10 +568,13 @@ runtime·sysconf(int32 name)
        return runtime·sysvicall6(libc·sysconf, 1, (uintptr)name);
 }
 
+extern void runtime·usleep1(uint32);
+
+#pragma textflag NOSPLIT
 void
-runtime·usleep(uint32 us)
+runtime·usleep(uint32 µs)
 {
-       runtime·sysvicall6(libc·usleep, 1, (uintptr)us);
+       runtime·usleep1(µs);
 }
 
 int32
@@ -580,8 +583,17 @@ runtime·write(uintptr fd, void* buf, int32 nbyte)
        return runtime·sysvicall6(libc·write, 3, (uintptr)fd, (uintptr)buf, (uintptr)nbyte);
 }
 
+extern void runtime·osyield1(void);
+
+#pragma textflag NOSPLIT
 void
 runtime·osyield(void)
 {
-       runtime·sysvicall6(libc·sched_yield, 0);
+       // Check the validity of m because we might be called in cgo callback
+       // path early enough where there isn't a m available yet.
+       if(g && g->m != nil) {
+               runtime·sysvicall6(libc·sched_yield, 0);
+               return;
+       }
+       runtime·osyield1();
 }

diff --git a/src/pkg/runtime/sys_solaris_amd64.s b/src/pkg/runtime/sys_solaris_amd64.s
index 83e8dfac562e66e74a7cf7e187a1a2e15463b332..1b18c8d9eb5fcc1448e1f62dbee0e25ad2425c53 100644 (file)
--- a/src/pkg/runtime/sys_solaris_amd64.s
+++ b/src/pkg/runtime/sys_solaris_amd64.s
@@ -270,3 +270,55 @@ exit:
 
        ADDQ    $184, SP
        RET
+
+// Called from runtime·usleep (Go). Can be called on Go stack, on OS stack,
+// can also be called in cgo callback path without a g->m.
+TEXT runtime·usleep1(SB),NOSPLIT,$0
+       MOVL    us+0(FP), DI
+       MOVQ    $runtime·usleep2(SB), AX // to hide from 6l
+
+       // Execute call on m->g0.
+       get_tls(R15)
+       CMPQ    R15, $0
+       JE      usleep1_noswitch
+
+       MOVQ    g(R15), R13
+       CMPQ    R13, $0
+       JE      usleep1_noswitch
+       MOVQ    g_m(R13), R13
+       CMPQ    R13, $0
+       JE      usleep1_noswitch
+       // TODO(aram): do something about the cpu profiler here.
+
+       MOVQ    m_g0(R13), R14
+       CMPQ    g(R15), R14
+       JNE     usleep1_switch
+       // executing on m->g0 already
+       CALL    AX
+       RET
+
+usleep1_switch:
+       // Switch to m->g0 stack and back.
+       MOVQ    (g_sched+gobuf_sp)(R14), R14
+       MOVQ    SP, -8(R14)
+       LEAQ    -8(R14), SP
+       CALL    AX
+       MOVQ    0(SP), SP
+       RET
+
+usleep1_noswitch:
+       // Not a Go-managed thread. Do not switch stack.
+       CALL    AX
+       RET
+
+// Runs on OS stack. duration (in µs units) is in DI.
+TEXT runtime·usleep2(SB),NOSPLIT,$0
+       MOVQ    libc·usleep(SB), AX
+       CALL    AX
+       RET
+
+// Runs on OS stack, called from runtime·osyield.
+TEXT runtime·osyield1(SB),NOSPLIT,$0
+       MOVQ    libc·sched_yield(SB), AX
+       CALL    AX
+       RET