runtime: convert g.waitreason from string to uint8

Every time I poke at #14921, the g.waitreason string
pointer writes show up.

They're not particularly important performance-wise,
but it'd be nice to clear the noise away.

And it does open up a few extra bytes in the g struct
for some future use.

Change-Id: I7ffbd52fbc2a286931a2218038fda52ed6473cc9
Reviewed-on: https://go-review.googlesource.com/99078
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/src/runtime/chan.go b/src/runtime/chan.go
index 10ee97d924..ce71cee4c5 100644
--- a/src/runtime/chan.go
+++ b/src/runtime/chan.go
@@ -142,7 +142,7 @@ func chansend(c *hchan, ep unsafe.Pointer, block bool, callerpc uintptr) bool {
 		if !block {
 			return false
 		}
-		gopark(nil, nil, "chan send (nil chan)", traceEvGoStop, 2)
+		gopark(nil, nil, waitReasonChanSendNilChan, traceEvGoStop, 2)
 		throw("unreachable")
 	}
 
@@ -231,7 +231,7 @@ func chansend(c *hchan, ep unsafe.Pointer, block bool, callerpc uintptr) bool {
 	gp.waiting = mysg
 	gp.param = nil
 	c.sendq.enqueue(mysg)
-	goparkunlock(&c.lock, "chan send", traceEvGoBlockSend, 3)
+	goparkunlock(&c.lock, waitReasonChanSend, traceEvGoBlockSend, 3)
 
 	// someone woke us up.
 	if mysg != gp.waiting {
@@ -426,7 +426,7 @@ func chanrecv(c *hchan, ep unsafe.Pointer, block bool) (selected, received bool)
 		if !block {
 			return
 		}
-		gopark(nil, nil, "chan receive (nil chan)", traceEvGoStop, 2)
+		gopark(nil, nil, waitReasonChanReceiveNilChan, traceEvGoStop, 2)
 		throw("unreachable")
 	}
 
@@ -517,7 +517,7 @@ func chanrecv(c *hchan, ep unsafe.Pointer, block bool) (selected, received bool)
 	mysg.c = c
 	gp.param = nil
 	c.recvq.enqueue(mysg)
-	goparkunlock(&c.lock, "chan receive", traceEvGoBlockRecv, 3)
+	goparkunlock(&c.lock, waitReasonChanReceive, traceEvGoBlockRecv, 3)
 
 	// someone woke us up
 	if mysg != gp.waiting {