runtime: make ncgocall a global counter

ncgocall was stored per M, runtime.NumCgoCall lost the counter when a M die.

Fixes #46789

Change-Id: I85831fbb2713f4c30d1800d07e1f47aa0031970e
GitHub-Last-Rev: cbc15fa
GitHub-Pull-Request: #46842
Reviewed-on: https://go-review.googlesource.com/c/go/+/329729
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Alexander Rakoczy <alex@golang.org>

src/runtime/cgocall.go

@@ -110,6 +110,8 @@ func syscall_cgocaller(fn unsafe.Pointer, args ...uintptr) uintptr {
  return as.retval
 }
 
+var ncgocall uint64 // number of cgo calls in total for dead m
+
 // Call from Go to C.
 //
 // This must be nosplit because it's used for syscalls on some

src/runtime/debug.go

@@ -45,7 +45,7 @@ func NumCPU() int {
 
 // NumCgoCall returns the number of cgo calls made by the current process.
 func NumCgoCall() int64 {
- var n int64
+ var n = int64(atomic.Load64(&ncgocall))
  for mp := (*m)(atomic.Loadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
  n += int64(mp.ncgocall)
  }

src/runtime/proc.go

@@ -1522,6 +1522,8 @@ found:
  }
  unlock(&sched.lock)
 
+ atomic.Xadd64(&ncgocall, int64(m.ncgocall))
+
  // Release the P.
  handoffp(releasep())
  // After this point we must not have write barriers.