runtime: don't panic in castogscanstatus

mknyszek · mknyszek · commit b5353fd90a38 · 2025-11-03T14:50:47.000-08:00
The panic calls gopanic which may have write barriers, but castogscanstatus is called from //go:nowritebarrier contexts. The panic is dead code anyway, and appears immediately before a call to 'throw'. Change-Id: I4a8e296b71bf002295a3aa1db4f723c305ed939a Reviewed-on: https://go-review.googlesource.com/c/go/+/717406 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
@@ -1254,8 +1254,8 @@ func castogscanstatus(gp *g, oldval, newval uint32) bool {
 		}
 	}
 	print("runtime: castogscanstatus oldval=", hex(oldval), " newval=", hex(newval), "\n")
-	throw("castogscanstatus")
-	panic("not reached")
+	throw("bad oldval passed to castogscanstatus")
+	return false
 }
 
 // casgstatusAlwaysTrack is a debug flag that causes casgstatus to always track

Original file line number	Diff line number	Diff line change
`@@ -1254,8 +1254,8 @@ func castogscanstatus(gp *g, oldval, newval uint32) bool {`
`1254`	`1254`	`}`
`1255`	`1255`	`}`
`1256`	`1256`	`print("runtime: castogscanstatus oldval=", hex(oldval), " newval=", hex(newval), "\n")`
`1257`		`- throw("castogscanstatus")`
`1258`		`- panic("not reached")`
	`1257`	`+ throw("bad oldval passed to castogscanstatus")`
	`1258`	`+ return false`
`1259`	`1259`	`}`
`1260`	`1260`
`1261`	`1261`	`// casgstatusAlwaysTrack is a debug flag that causes casgstatus to always track`