runtime: fix tracing of syscallexit

There were two issues.
1. Delayed EvGoSysExit could have been emitted during TraceStart,
while it had not yet emitted EvGoInSyscall.
2. Delayed EvGoSysExit could have been emitted during next tracing session.

Fixes #10476
Fixes #11262

Change-Id: Iab68eb31cf38eb6eb6eee427f49c5ca0865a8c64
Reviewed-on: https://go-review.googlesource.com/9132
Reviewed-by: Russ Cox <rsc@golang.org>

1 files changed, 36 insertions, 33 deletions

diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 4f6a8ec7e3..d2dfa71edd 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -220,39 +220,41 @@ type g struct {
 	stackguard0 uintptr // offset known to liblink
 	stackguard1 uintptr // offset known to liblink
 
-	_panic       *_panic // innermost panic - offset known to liblink
-	_defer       *_defer // innermost defer
-	stackAlloc   uintptr // stack allocation is [stack.lo,stack.lo+stackAlloc)
-	sched        gobuf
-	syscallsp    uintptr        // if status==Gsyscall, syscallsp = sched.sp to use during gc
-	syscallpc    uintptr        // if status==Gsyscall, syscallpc = sched.pc to use during gc
-	stkbar       []stkbar       // stack barriers, from low to high
-	stkbarPos    uintptr        // index of lowest stack barrier not hit
-	param        unsafe.Pointer // passed parameter on wakeup
-	atomicstatus uint32
-	goid         int64
-	waitsince    int64  // approx time when the g become blocked
-	waitreason   string // if status==Gwaiting
-	schedlink    guintptr
-	preempt      bool // preemption signal, duplicates stackguard0 = stackpreempt
-	paniconfault bool // panic (instead of crash) on unexpected fault address
-	preemptscan  bool // preempted g does scan for gc
-	gcscandone   bool // g has scanned stack; protected by _Gscan bit in status
-	gcscanvalid  bool // false at start of gc cycle, true if G has not run since last scan
-	throwsplit   bool // must not split stack
-	raceignore   int8 // ignore race detection events
-	m            *m   // for debuggers, but offset not hard-coded
-	lockedm      *m
-	sig          uint32
-	writebuf     []byte
-	sigcode0     uintptr
-	sigcode1     uintptr
-	sigpc        uintptr
-	gopc         uintptr // pc of go statement that created this goroutine
-	startpc      uintptr // pc of goroutine function
-	racectx      uintptr
-	waiting      *sudog // sudog structures this g is waiting on (that have a valid elem ptr)
-	readyg       *g     // scratch for readyExecute
+	_panic         *_panic // innermost panic - offset known to liblink
+	_defer         *_defer // innermost defer
+	stackAlloc     uintptr // stack allocation is [stack.lo,stack.lo+stackAlloc)
+	sched          gobuf
+	syscallsp      uintptr        // if status==Gsyscall, syscallsp = sched.sp to use during gc
+	syscallpc      uintptr        // if status==Gsyscall, syscallpc = sched.pc to use during gc
+	stkbar         []stkbar       // stack barriers, from low to high
+	stkbarPos      uintptr        // index of lowest stack barrier not hit
+	param          unsafe.Pointer // passed parameter on wakeup
+	atomicstatus   uint32
+	goid           int64
+	waitsince      int64  // approx time when the g become blocked
+	waitreason     string // if status==Gwaiting
+	schedlink      guintptr
+	preempt        bool  // preemption signal, duplicates stackguard0 = stackpreempt
+	paniconfault   bool  // panic (instead of crash) on unexpected fault address
+	preemptscan    bool  // preempted g does scan for gc
+	gcscandone     bool  // g has scanned stack; protected by _Gscan bit in status
+	gcscanvalid    bool  // false at start of gc cycle, true if G has not run since last scan
+	throwsplit     bool  // must not split stack
+	raceignore     int8  // ignore race detection events
+	sysblocktraced bool  // StartTrace has emitted EvGoInSyscall about this goroutine
+	sysexitticks   int64 // cputicks when syscall has returned (for tracing)
+	m              *m    // for debuggers, but offset not hard-coded
+	lockedm        *m
+	sig            uint32
+	writebuf       []byte
+	sigcode0       uintptr
+	sigcode1       uintptr
+	sigpc          uintptr
+	gopc           uintptr // pc of go statement that created this goroutine
+	startpc        uintptr // pc of goroutine function
+	racectx        uintptr
+	waiting        *sudog // sudog structures this g is waiting on (that have a valid elem ptr)
+	readyg         *g     // scratch for readyExecute
 
 	// Per-G gcController state
 	gcalloc    uintptr // bytes allocated during this GC cycle
@@ -320,6 +322,7 @@ type m struct {
 	waitlock      unsafe.Pointer
 	waittraceev   byte
 	waittraceskip int
+	startingtrace bool
 	syscalltick   uint32
 	//#ifdef GOOS_windows
 	thread uintptr // thread handle