runtime: allow per-OS changes to unix profiler

Updates #35057

Change-Id: I56ea8f4750022847f0866c85e237a2cea40e0ff7
Reviewed-on: https://go-review.googlesource.com/c/go/+/342053
Run-TryBot: Rhys Hiltner <rhys@justin.tv>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
Trust: Michael Knyszek <mknyszek@google.com>

src/runtime/os3_solaris.go

@@ -289,6 +289,19 @@ func sigdelset(mask *sigset, i int) {
 func (c *sigctxt) fixsigcode(sig uint32) {
 }
 
+func setProcessCPUProfiler(hz int32) {
+	setProcessCPUProfilerTimer(hz)
+}
+
+func setThreadCPUProfiler(hz int32) {
+	setThreadCPUProfilerHz(hz)
+}
+
+//go:nosplit
+func validSIGPROF(mp *m, c *sigctxt) bool {
+	return true
+}
+
 //go:nosplit
 func semacreate(mp *m) {
 	if mp.waitsema != 0 {

src/runtime/os_aix.go

@@ -323,6 +323,19 @@ func sigdelset(mask *sigset, i int) {
 	(*mask)[(i-1)/64] &^= 1 << ((uint32(i) - 1) & 63)
 }
 
+func setProcessCPUProfiler(hz int32) {
+	setProcessCPUProfilerTimer(hz)
+}
+
+func setThreadCPUProfiler(hz int32) {
+	setThreadCPUProfilerHz(hz)
+}
+
+//go:nosplit
+func validSIGPROF(mp *m, c *sigctxt) bool {
+	return true
+}
+
 const (
 	_CLOCK_REALTIME  = 9
 	_CLOCK_MONOTONIC = 10

src/runtime/os_darwin.go

@@ -425,6 +425,19 @@ func sigdelset(mask *sigset, i int) {
 	*mask &^= 1 << (uint32(i) - 1)
 }
 
+func setProcessCPUProfiler(hz int32) {
+	setProcessCPUProfilerTimer(hz)
+}
+
+func setThreadCPUProfiler(hz int32) {
+	setThreadCPUProfilerHz(hz)
+}
+
+//go:nosplit
+func validSIGPROF(mp *m, c *sigctxt) bool {
+	return true
+}
+
 //go:linkname executablePath os.executablePath
 var executablePath string
 

src/runtime/os_dragonfly.go

@@ -268,6 +268,19 @@ func sigdelset(mask *sigset, i int) {
 func (c *sigctxt) fixsigcode(sig uint32) {
 }
 
+func setProcessCPUProfiler(hz int32) {
+	setProcessCPUProfilerTimer(hz)
+}
+
+func setThreadCPUProfiler(hz int32) {
+	setThreadCPUProfilerHz(hz)
+}
+
+//go:nosplit
+func validSIGPROF(mp *m, c *sigctxt) bool {
+	return true
+}
+
 func sysargs(argc int32, argv **byte) {
 	n := argc + 1
 

src/runtime/os_freebsd.go

@@ -380,6 +380,19 @@ func sigdelset(mask *sigset, i int) {
 func (c *sigctxt) fixsigcode(sig uint32) {
 }
 
+func setProcessCPUProfiler(hz int32) {
+	setProcessCPUProfilerTimer(hz)
+}
+
+func setThreadCPUProfiler(hz int32) {
+	setThreadCPUProfilerHz(hz)
+}
+
+//go:nosplit
+func validSIGPROF(mp *m, c *sigctxt) bool {
+	return true
+}
+
 func sysargs(argc int32, argv **byte) {
 	n := argc + 1
 

src/runtime/os_linux.go

@@ -517,3 +517,19 @@ func tgkill(tgid, tid, sig int)
 func signalM(mp *m, sig int) {
 	tgkill(getpid(), int(mp.procid), sig)
 }
+
+func setProcessCPUProfiler(hz int32) {
+	setProcessCPUProfilerTimer(hz)
+}
+
+func setThreadCPUProfiler(hz int32) {
+	setThreadCPUProfilerHz(hz)
+}
+
+//go:nosplit
+func validSIGPROF(mp *m, c *sigctxt) bool {
+	// Once the profiler for Linux uses timer_create, this function will need to
+	// do more than return true. But so long as the only profiling timer in use
+	// is setitimer, returning true is correct.
+	return true
+}

src/runtime/os_netbsd.go

@@ -371,6 +371,19 @@ func sigdelset(mask *sigset, i int) {
 func (c *sigctxt) fixsigcode(sig uint32) {
 }
 
+func setProcessCPUProfiler(hz int32) {
+	setProcessCPUProfilerTimer(hz)
+}
+
+func setThreadCPUProfiler(hz int32) {
+	setThreadCPUProfilerHz(hz)
+}
+
+//go:nosplit
+func validSIGPROF(mp *m, c *sigctxt) bool {
+	return true
+}
+
 func sysargs(argc int32, argv **byte) {
 	n := argc + 1
 

src/runtime/os_openbsd.go

@@ -233,6 +233,19 @@ func sigdelset(mask *sigset, i int) {
 func (c *sigctxt) fixsigcode(sig uint32) {
 }
 
+func setProcessCPUProfiler(hz int32) {
+	setProcessCPUProfilerTimer(hz)
+}
+
+func setThreadCPUProfiler(hz int32) {
+	setThreadCPUProfilerHz(hz)
+}
+
+//go:nosplit
+func validSIGPROF(mp *m, c *sigctxt) bool {
+	return true
+}
+
 var haveMapStack = false
 
 func osStackAlloc(s *mspan) {

src/runtime/signal_unix.go

@@ -263,11 +263,11 @@ func clearSignalHandlers() {
 	}
 }
 
-// setProcessCPUProfiler is called when the profiling timer changes.
-// It is called with prof.lock held. hz is the new timer, and is 0 if
+// setProcessCPUProfilerTimer is called when the profiling timer changes.
+// It is called with prof.signalLock held. hz is the new timer, and is 0 if
 // profiling is being disabled. Enable or disable the signal as
 // required for -buildmode=c-archive.
-func setProcessCPUProfiler(hz int32) {
+func setProcessCPUProfilerTimer(hz int32) {
 	if hz != 0 {
 		// Enable the Go signal handler if not enabled.
 		if atomic.Cas(&handlingSig[_SIGPROF], 0, 1) {
@@ -309,10 +309,10 @@ func setProcessCPUProfiler(hz int32) {
 	}
 }
 
-// setThreadCPUProfiler makes any thread-specific changes required to
+// setThreadCPUProfilerHz makes any thread-specific changes required to
 // implement profiling at a rate of hz.
-// No changes required on Unix systems.
-func setThreadCPUProfiler(hz int32) {
+// No changes required on Unix systems when using setitimer.
+func setThreadCPUProfilerHz(hz int32) {
 	getg().m.profilehz = hz
 }
 
@@ -423,7 +423,11 @@ func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {
 	setg(g)
 	if g == nil {
 		if sig == _SIGPROF {
-			sigprofNonGoPC(c.sigpc())
+			// Some platforms (Linux) have per-thread timers, which we use in
+			// combination with the process-wide timer. Avoid double-counting.
+			if validSIGPROF(nil, c) {
+				sigprofNonGoPC(c.sigpc())
+			}
 			return
 		}
 		if sig == sigPreempt && preemptMSupported && debug.asyncpreemptoff == 0 {
@@ -540,7 +544,12 @@ func sighandler(sig uint32, info *siginfo, ctxt unsafe.Pointer, gp *g) {
 	c := &sigctxt{info, ctxt}
 
 	if sig == _SIGPROF {
-		sigprof(c.sigpc(), c.sigsp(), c.siglr(), gp, _g_.m)
+		mp := _g_.m
+		// Some platforms (Linux) have per-thread timers, which we use in
+		// combination with the process-wide timer. Avoid double-counting.
+		if validSIGPROF(mp, c) {
+			sigprof(c.sigpc(), c.sigsp(), c.siglr(), gp, mp)
+		}
 		return
 	}