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bug in async select read

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buganizer 1589219
channel is returning same values multiple times

R=r
OCL=23447
CL=23447
This commit is contained in:
Ken Thompson 2009-01-24 15:58:44 -08:00
parent d2117ad438
commit 3338c71fc6
1 changed files with 22 additions and 19 deletions
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41
src/runtime/chan.c
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@ -5,6 +5,7 @@
#include "runtime.h"
static int32 debug = 0;
static int32 xxx = 0;
static Lock chanlock;
typedef struct Hchan Hchan;
@ -17,8 +18,9 @@ typedef struct Scase Scase;
struct SudoG
{
G* g; // g and selgen constitute
int16 offset; // offset of case number
int32 selgen; // a weak pointer to g
int16 offset; // offset of case number
int8 isfree; // offset of case number
SudoG* link;
byte elem[8]; // synch data element (+ more)
};
@ -206,7 +208,6 @@ sendchan(Hchan *c, byte *ep, bool *pres)
return;
asynch:
//prints("\nasend\n");
while(c->qcount >= c->dataqsiz) {
if(pres != nil) {
unlock(&chanlock);
@ -229,10 +230,8 @@ asynch:
sg = dequeue(&c->recvq, c);
if(sg != nil) {
gp = sg->g;
gp->param = sg;
freesg(c, sg);
unlock(&chanlock);
//prints("wakeup\n");
ready(gp);
} else
unlock(&chanlock);
@ -312,7 +311,6 @@ asynch:
sg = dequeue(&c->sendq, c);
if(sg != nil) {
gp = sg->g;
gp->param = sg;
freesg(c, sg);
unlock(&chanlock);
ready(gp);
@ -411,7 +409,7 @@ sys·newselect(int32 size, Select *sel)
if(debug) {
prints("newselect s=");
sys·printpointer(sel);
prints("newselect size=");
prints(" size=");
sys·printint(size);
prints("\n");
}
@ -451,7 +449,7 @@ sys·selectsend(Select *sel, Hchan *c, ...)
c->elemalg->copy(c->elemsize, cas->u.elem, ae);
if(debug) {
prints("newselect s=");
prints("selectsend s=");
sys·printpointer(sel);
prints(" pc=");
sys·printpointer(cas->pc);
@ -495,7 +493,7 @@ sys·selectrecv(Select *sel, Hchan *c, ...)
cas->u.elemp = *(byte**)((byte*)&sel + eo);
if(debug) {
prints("newselect s=");
prints("selectrecv s=");
sys·printpointer(sel);
prints(" pc=");
sys·printpointer(cas->pc);
@ -510,7 +508,7 @@ sys·selectrecv(Select *sel, Hchan *c, ...)
}
// selectrecv(sel *byte) (selected bool);
// selectdefaul(sel *byte) (selected bool);
void
sys·selectdefault(Select *sel, ...)
{
@ -534,7 +532,7 @@ sys·selectdefault(Select *sel, ...)
cas->u.elemp = nil;
if(debug) {
prints("newselect s=");
prints("selectdefault s=");
sys·printpointer(sel);
prints(" pc=");
sys·printpointer(cas->pc);
@ -546,7 +544,6 @@ sys·selectdefault(Select *sel, ...)
}
}
uint32 xxx = 0;
// selectgo(sel *byte);
void
@ -589,6 +586,7 @@ sys·selectgo(Select *sel)
lock(&chanlock);
loop:
// pass 1 - look for something already waiting
dfl = nil;
for(i=0; i<sel->ncase; i++) {
@ -688,16 +686,25 @@ sys·selectgo(Select *sel)
o -= sel->ncase;
}
g->param = nil;
g->status = Gwaiting;
unlock(&chanlock);
sys·Gosched();
lock(&chanlock);
sg = g->param;
if(sg == nil)
goto loop;
o = sg->offset;
cas = sel->scase[o];
c = cas->chan;
if(c->dataqsiz > 0) {
// prints("shouldnt happen\n");
goto loop;
}
if(xxx) {
prints("wait-return: sel=");
sys·printpointer(sel);
@ -712,12 +719,6 @@ sys·selectgo(Select *sel)
prints("\n");
}
if(c->dataqsiz > 0) {
if(cas->send)
goto asyns;
goto asynr;
}
if(!cas->send) {
if(cas->u.elemp != nil)
c->elemalg->copy(c->elemsize, cas->u.elemp, sg->elem);
@ -734,7 +735,6 @@ asynr:
sg = dequeue(&c->sendq, c);
if(sg != nil) {
gp = sg->g;
gp->param = sg;
freesg(c, sg);
ready(gp);
}
@ -748,7 +748,6 @@ asyns:
sg = dequeue(&c->recvq, c);
if(sg != nil) {
gp = sg->g;
gp->param = sg;
freesg(c, sg);
ready(gp);
}
@ -849,6 +848,7 @@ allocsg(Hchan *c)
sg->selgen = g->selgen;
sg->g = g;
sg->offset = 0;
sg->isfree = 0;
return sg;
}
@ -856,6 +856,9 @@ allocsg(Hchan *c)
static void
freesg(Hchan *c, SudoG *sg)
{
if(sg->isfree)
throw("chan.freesg: already free");
sg->isfree = 1;
sg->link = c->free;
c->free = sg;
}