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runtime: fix select pass 3

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Fixes #2075

R=rsc, ken, r
CC=golang-dev
https://golang.org/cl/4748045
This commit is contained in:
Hector Chu 2011-07-18 16:15:01 -04:00 committed by Russ Cox
parent bd77619142
commit 47e6042f73
2 changed files with 40 additions and 3 deletions
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7
src/pkg/runtime/chan.c
View File

@ -1167,12 +1167,15 @@ loop:
static void
dequeueg(WaitQ *q, Hchan *c)
{
SudoG **l, *sgp;
SudoG **l, *sgp, *prevsgp;
for(l=&q->first; (sgp=*l) != nil; l=&sgp->link) {
prevsgp = nil;
for(l=&q->first; (sgp=*l) != nil; l=&sgp->link, prevsgp=sgp) {
if(sgp->g == g) {
*l = sgp->link;
freesg(c, sgp);
if(q->last == sgp)
q->last = prevsgp;
break;
}
}

34
test/chan/select6.go Normal file
View File

@ -0,0 +1,34 @@
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Issue 2075
// A bug in select corrupts channel queues of failed cases
// if there are multiple waiters on those channels and the
// select is the last in the queue. If further waits are made
// on the channel without draining it first then those waiters
// will never wake up. In the code below c1 is such a channel.
package main
func main() {
c1 := make(chan bool)
c2 := make(chan bool)
c3 := make(chan bool)
go func() { <-c1 }()
go func() {
select {
case <-c1:
panic("dummy")
case <-c2:
c3 <- true
}
<-c1
}()
go func() { c2 <- true }()
<-c3
c1 <- true
c1 <- true
}