On Thu, Sep 16, 2010 at 11:02 PM, erik quanstrom <[email protected]> wrote:
> i have these processes all deadlocked. 8.out
> is serving /n/mntpt.
>
> xxx 11921346 0:00 0:00 436K Create 8.out
> xxx 11921785 0:00 0:00 24K Open cat /n/mntpt/sos
> xxx 11921786 0:00 0:00 24K Unmount unmount /n/mntpt
> xxx 11921787 0:00 0:00 44K Pwrite echo x y
okay, it's not. sorry for the confusion. the reason
for looking at that case was that it seemed at the
time related to a crash here on the indirection
of mh->mount, which is nil. the code in question
was a fileserver which was crashing, getting killed
while concurrent io was being done to the fs.
/sys/src/9/port/chan.c:1009,1019
if((wq = ewalk(c, nil, names+nhave, ntry)) == nil){
/* try a union mount, if any */
if(mh && !nomount){
/*
* mh->mount->to == c, so start at
mh->mount->next
*/
rlock(&mh->lock);
for(f = mh->mount->next; f; f = f->next)
if((wq = ewalk(f->to, nil, names+nhave,
ntry)) != nil)
break;
i don't know why it can't be nil, since the code here
doesn't have a lock. i think this might be the solution,
but i haven't done a careful lock audit to be sure
/usr/quanstro/src/ysk/port/chan.c:1009,1021
if((wq = ewalk(c, nil, names+nhave, ntry)) == nil){
/* try a union mount, if any */
if(mh && !nomount){
/*
* mh->mount->to == c, so start at
mh->mount->next
*/
>> f = nil;
rlock(&mh->lock);
>> if(mh->mount)
for(f = mh->mount->next; f; f = f->next)
if((wq = ewalk(f->to, nil, names+nhave,
ntry)) != nil)
break;
runlock(&mh->lock);
- erik
