xfnw/plan9fox
1
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity

nusb/usbd: serialize /dev/usbevent processing

Browse source 
when there are multiple readers of /dev/usbevent, we have to
serialize the processing to make sure that only one driver
is opening the devices control endpoint at a time.

to do this, we assume the device is busy after reading the
event file until the next read or clunk on the same fid.

to mark a device busy, we set the dev->aux pointer to the
fid processing a event. And the Event structure takes a
reference to the device producing the event.

the problem arised from cdc ethernet and nusb/serial sharing
the same device class, and we need to run the particular driver
to figure out if the device can be used. doing this concurrently
fails because devusb allows only one open per endpoint.
This commit is contained in:
cinap_lenrek 2014-06-03 07:21:48 +02:00
parent 1427ba3126
commit 5ab9f9c621
1 changed files with 80 additions and 49 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

129
sys/src/cmd/nusb/usbd/usbd.c
View file

@ -23,13 +23,15 @@ static char Enonexist[] = "does not exist";
typedef struct Event Event;
struct Event {
Dev *dev; /* the device producing the event,
dev->aux points to Fid processing the event */
char *data;
int len;
Event *link;
int ref; /* number of readers which will read this one
the next time they'll read */
int prev; /* number of events pointing to this one with
their link pointers */
int ref; /* number of readers which will read this one
the next time they'll read */
int prev; /* number of events pointing to this one with
their link pointers */
};
static Event *evlast;
@ -74,58 +76,66 @@ putevent(Event *e)
if(e->ref || e->prev)
return ee;
ee->prev--;
closedev(e->dev);
free(e->data);
free(e);
return ee;
}
static void
readevent(Req *req)
procreqs(void)
{
Req *r, *p, *x;
Event *e;
Fid *f;
qlock(&evlock);
e = req->fid->aux;
if(e == evlast){
addreader(req);
qunlock(&evlock);
return;
Loop:
for(p = nil, r = reqfirst; r != nil; p = r, r = x){
x = (Req*)r->aux;
f = r->fid;
e = (Event*)f->aux;
if(e == evlast)
continue;
if(e->dev->aux == f){
e->dev->aux = nil; /* release device */
e->ref--;
e = putevent(e);
e->ref++;
f->aux = e;
goto Loop;
}
if(e->dev->aux == nil){
e->dev->aux = f; /* claim device */
if(x == nil)
reqlast = p;
if(p == nil)
reqfirst = x;
else
p->aux = x;
r->aux = nil;
fulfill(r, e);
respond(r, nil);
goto Loop;
}
}
fulfill(req, e);
req->fid->aux = e->link;
e->link->ref++;
e->ref--;
putevent(e);
qunlock(&evlock);
respond(req, nil);
}
static void
pushevent(char *data)
pushevent(Dev *d, char *data)
{
Event *e, *ee;
Req *r, *rr;
Event *e;
qlock(&evlock);
e = evlast;
ee = emallocz(sizeof(Event), 1);
evlast = ee;
evlast = emallocz(sizeof(Event), 1);
incref(d);
e->dev = d;
e->data = data;
e->len = strlen(data);
e->link = ee;
ee->prev++;
for(r = reqfirst; r != nil; r = rr){
rr = r->aux;
r->aux = nil;
r->fid->aux = ee;
ee->ref++;
e->ref--;
fulfill(r, e);
respond(r, nil);
}
e->link = evlast;
evlast->prev++;
procreqs();
putevent(e);
reqfirst = nil;
reqlast = nil;
qunlock(&evlock);
}
@ -192,7 +202,10 @@ usbdread(Req *req)
respond(req, "the front fell off");
return;
}
readevent(req);
qlock(&evlock);
addreader(req);
procreqs();
qunlock(&evlock);
break;
default:
respond(req, Enonexist);
@ -226,16 +239,19 @@ enumerate(Event **l)
Event *e;
Hub *h;
Port *p;
Dev *d;
int i;
for(h = hubs; h != nil; h = h->next){
for(i = 1; i <= h->nport; i++){
p = &h->port[i];
if(p->dev == nil || p->dev->usb == nil || p->hub != nil)
d = p->dev;
if(d == nil || d->usb == nil || p->hub != nil)
continue;
e = emallocz(sizeof(Event), 1);
e->data = formatdev(p->dev, 0);
incref(d);
e->dev = d;
e->data = formatdev(d, 0);
e->len = strlen(e->data);
e->prev = 1;
*l = e;
@ -277,6 +293,10 @@ usbddestroyfid(Fid *fid)
if(fid->qid.path == Qusbevent && fid->aux != nil){
qlock(&evlock);
e = fid->aux;
if(e->dev != nil && e->dev->aux == fid){
e->dev->aux = nil; /* release device */
procreqs();
}
if(--e->ref == 0 && e->prev == 0)
while(e->ref == 0 && e->prev == 0 && e != evlast)
e = putevent(e);
@ -287,18 +307,24 @@ usbddestroyfid(Fid *fid)
static void
usbdflush(Req *req)
{
Req **l, *r;
Req *r, *p, *x;
qlock(&evlock);
l = &reqfirst;
while(r = *l){
for(p = nil, r = reqfirst; r != nil; p = r, r = x){
x = (Req*)r->aux;
if(r == req->oldreq){
*l = r->aux;
if(x == nil)
reqlast = p;
if(p == nil)
reqfirst = x;
else
p->aux = x;
r->aux = nil;
respond(r, "interrupted");
break;
}
l = &r->aux;
}
qunlock(&evlock);
respond(req->oldreq, "interrupted");
respond(req, nil);
}
@ -331,16 +357,21 @@ attachdev(Port *p)
close(d->dfd);
d->dfd = -1;
pushevent(formatdev(d, 0));
d->aux = nil; /* device initially unclaimed */
pushevent(d, formatdev(d, 0));
return 0;
}
void
detachdev(Port *p)
{
if(p->dev->usb->class == Clhub)
Dev *d;
d = p->dev;
if(d->usb->class == Clhub)
return;
pushevent(formatdev(p->dev, 1));
pushevent(d, formatdev(d, 1));
}
void