runtime: better error message for newosproc failure

If creating a new thread fails with EAGAIN, point the user at ulimit.

Fixes #15476.

Change-Id: Ib36519614b5c72776ea7f218a0c62df1dd91a8ea
Reviewed-on: https://go-review.googlesource.com/24570
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/os3_solaris.go

@@ -165,6 +165,9 @@ func newosproc(mp *m, _ unsafe.Pointer) {
 	sigprocmask(_SIG_SETMASK, &oset, nil)
 	if ret != 0 {
 		print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", ret, ")\n")
+		if ret == -_EAGAIN {
+			println("runtime: may need to increase max user processes (ulimit -u)")
+		}
 		throw("newosproc")
 	}
 }

src/runtime/os_dragonfly.go

@@ -134,6 +134,7 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 		tid2:       nil,
 	}
 
+	// TODO: Check for error.
 	lwp_create(&params)
 	sigprocmask(_SIG_SETMASK, &oset, nil)
 }

src/runtime/os_freebsd.go

@@ -121,6 +121,7 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 
 	var oset sigset
 	sigprocmask(_SIG_SETMASK, &sigset_all, &oset)
+	// TODO: Check for error.
 	thr_new(&param, int32(unsafe.Sizeof(param)))
 	sigprocmask(_SIG_SETMASK, &oset, nil)
 }

src/runtime/os_linux.go

@@ -154,6 +154,9 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 
 	if ret < 0 {
 		print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", -ret, ")\n")
+		if ret == -_EAGAIN {
+			println("runtime: may need to increase max user processes (ulimit -u)")
+		}
 		throw("newosproc")
 	}
 }

src/runtime/os_netbsd.go

@@ -20,6 +20,8 @@ const (
 	// From NetBSD's <sys/ucontext.h>
 	_UC_SIGMASK = 0x01
 	_UC_CPU     = 0x04
+
+	_EAGAIN = 35
 )
 
 type mOS struct {
@@ -162,6 +164,9 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 	ret := lwp_create(unsafe.Pointer(&uc), 0, unsafe.Pointer(&mp.procid))
 	if ret < 0 {
 		print("runtime: failed to create new OS thread (have ", mcount()-1, " already; errno=", -ret, ")\n")
+		if ret == -_EAGAIN {
+			println("runtime: may need to increase max user processes (ulimit -p)")
+		}
 		throw("runtime.newosproc")
 	}
 }

src/runtime/os_openbsd.go

@@ -154,6 +154,9 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 
 	if ret < 0 {
 		print("runtime: failed to create new OS thread (have ", mcount()-1, " already; errno=", -ret, ")\n")
+		if ret == -_EAGAIN {
+			println("runtime: may need to increase max user processes (ulimit -p)")
+		}
 		throw("runtime.newosproc")
 	}
 }