diff options
| -rw-r--r-- | src/pkg/runtime/chan.c | 6 | ||||
| -rw-r--r-- | src/pkg/runtime/runtime.h | 2 | ||||
| -rw-r--r-- | test/chan/doubleselect.go | 83 | ||||
| -rw-r--r-- | test/golden.out | 3 |
4 files changed, 89 insertions, 5 deletions
diff --git a/src/pkg/runtime/chan.c b/src/pkg/runtime/chan.c index f0202cf66..b2a0b4fac 100644 --- a/src/pkg/runtime/chan.c +++ b/src/pkg/runtime/chan.c @@ -24,7 +24,7 @@ typedef struct Scase Scase; struct SudoG { G* g; // g and selgen constitute - int32 selgen; // a weak pointer to g + uint32 selgen; // a weak pointer to g int16 offset; // offset of case number int8 isfree; // offset of case number SudoG* link; @@ -982,14 +982,12 @@ loop: q->first = sgp->link; // if sgp is stale, ignore it - if(sgp->selgen != sgp->g->selgen) { + if(!cas(&sgp->g->selgen, sgp->selgen, sgp->selgen + 1)) { //prints("INVALID PSEUDOG POINTER\n"); freesg(c, sgp); goto loop; } - // invalidate any others - sgp->g->selgen++; return sgp; } diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h index 91130a005..8052fd09c 100644 --- a/src/pkg/runtime/runtime.h +++ b/src/pkg/runtime/runtime.h @@ -167,7 +167,7 @@ struct G void* param; // passed parameter on wakeup int16 status; int32 goid; - int32 selgen; // valid sudog pointer + uint32 selgen; // valid sudog pointer G* schedlink; bool readyonstop; M* m; // for debuggers, but offset not hard-coded diff --git a/test/chan/doubleselect.go b/test/chan/doubleselect.go new file mode 100644 index 000000000..53dafeb1a --- /dev/null +++ b/test/chan/doubleselect.go @@ -0,0 +1,83 @@ +// $G $D/$F.go && $L $F.$A && ./$A.out + +// Copyright 2009 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. + +// This test is designed to flush out the case where two cases of a select can +// both end up running. See http://codereview.appspot.com/180068. +package main + +import ( + "flag" + "runtime" +) + +var iterations *int = flag.Int("n", 100000, "number of iterations") + +// sender sends a counter to one of four different channels. If two +// cases both end up running in the same iteration, the same value will be sent +// to two different channels. +func sender(n int, c1, c2, c3, c4 chan<- int) { + defer close(c1) + defer close(c2) + + for i := 0; i < n; i++ { + select { + case c1 <- i: + case c2 <- i: + case c3 <- i: + case c4 <- i: + } + } +} + +// mux receives the values from sender and forwards them onto another channel. +// It would be simplier to just have sender's four cases all be the same +// channel, but this doesn't actually trigger the bug. +func mux(out chan<- int, in <-chan int) { + for { + v := <-in + if closed(in) { + close(out) + break + } + out <- v + } +} + +// recver gets a steam of values from the four mux's and checks for duplicates. +func recver(in <-chan int) { + seen := make(map[int]bool) + + for { + v := <-in + if closed(in) { + break + } + if _, ok := seen[v]; ok { + panic("got duplicate value: ", v) + } + seen[v] = true + } +} + +func main() { + runtime.GOMAXPROCS(2) + + c1 := make(chan int) + c2 := make(chan int) + c3 := make(chan int) + c4 := make(chan int) + cmux := make(chan int) + go sender(*iterations, c1, c2, c3, c4) + go mux(cmux, c1) + go mux(cmux, c2) + go mux(cmux, c3) + go mux(cmux, c4) + // We keep the recver because it might catch more bugs in the future. + // However, the result of the bug linked to at the top is that we'll + // end up panicing with: "throw: bad g->status in ready". + recver(cmux) + print("PASS\n") +} diff --git a/test/golden.out b/test/golden.out index 9813c8313..063feccd0 100644 --- a/test/golden.out +++ b/test/golden.out @@ -75,6 +75,9 @@ abcxyz-abcxyz-abcxyz-abcxyz-abcxyz-abcxyz-abcxyz == chan/ +=========== chan/doubleselect.go +PASS + =========== chan/nonblock.go PASS |