[9fans] kernel tag bug?

[9fans] kernel tag bug?

[erik quanstrom]

it looks like devcons is suffering from some sort of tag collision.
a Rwrite is coming back for a Tread.

Sat Jan 24 09:43:47: mnt: proc rc 10946: mismatch from /mnt/temp/data /dev/cons rep 0xf63661a8 tag 1 fid 1170 T116 R119 rp 1
Sat Jan 24 10:06:26: unexpected reply tag 1; type 117
Fri Jan 30 15:21:48: 336082 page: checked 75 page table entries
Wed Mar 18 11:27:27: mnt: proc rc 4632855: mismatch from /mnt/temp/data /dev/cons rep 0xf69e84e8 tag 37 fid 5644 T116 R119 rp 37

i don't immediately see the cause of the problem.

- erik

Re: [9fans] kernel tag bug?

[Russ Cox]

On Tue, Mar 24, 2009 at 10:59 AM, erik quanstrom <quanstro@quanstro.net> wrote:
> it looks like devcons is suffering from some sort of tag collision.
> a Rwrite is coming back for a Tread.
>
> Sat Jan 24 09:43:47: mnt: proc rc 10946: mismatch from /mnt/temp/data /dev/cons rep 0xf63661a8 tag 1 fid 1170 T116 R119 rp 1
> Sat Jan 24 10:06:26: unexpected reply tag 1; type 117
> Fri Jan 30 15:21:48: 336082 page: checked 75 page table entries
> Wed Mar 18 11:27:27: mnt: proc rc 4632855: mismatch from /mnt/temp/data /dev/cons rep 0xf69e84e8 tag 37 fid 5644 T116 R119 rp 37
>
> i don't immediately see the cause of the problem.

i've seen this for years in various forms
but it had never happened regularly enough
to track down, and it was never clear that it
was the kernel's fault (and not, say, the 9p server).

if you want to look for the problem, you might
find it easier in 9vx.  i see it in 9vx all the time
if i interrupt an outstanding 9p message by
typing DEL.  9fs sources; ls /n/sources; DEL
on a slow connection, for example.

russ

Re: [9fans] kernel tag bug?

[erik quanstrom]

On Tue Mar 24 16:00:54 EDT 2009, rsc@swtch.com wrote:
> On Tue, Mar 24, 2009 at 10:59 AM, erik quanstrom <quanstro@quanstro.net> wrote:
> > it looks like devcons is suffering from some sort of tag collision.
> > a Rwrite is coming back for a Tread.
> >
> > Sat Jan 24 09:43:47: mnt: proc rc 10946: mismatch from /mnt/temp/data /dev/cons rep 0xf63661a8 tag 1 fid 1170 T116 R119 rp 1
> > Sat Jan 24 10:06:26: unexpected reply tag 1; type 117
> > Fri Jan 30 15:21:48: 336082 page: checked 75 page table entries
> > Wed Mar 18 11:27:27: mnt: proc rc 4632855: mismatch from /mnt/temp/data /dev/cons rep 0xf69e84e8 tag 37 fid 5644 T116 R119 rp 37
> >
> > i don't immediately see the cause of the problem.
>
> i've seen this for years in various forms
> but it had never happened regularly enough
> to track down, and it was never clear that it
> was the kernel's fault (and not, say, the 9p server).

doesn't the kernel get credit either way?  either
it's the source (devmnt) or the server (devcons).
am i missing something?

> if i interrupt an outstanding 9p message by
> typing DEL.  9fs sources; ls /n/sources; DEL

interesting.  maybe the read was interrupted.
devmnt picked the same tag for a write and
immediately got the interrupted read back.

- erik

Re: [9fans] kernel tag bug?

[Russ Cox]

> doesn't the kernel get credit either way?  either
> it's the source (devmnt) or the server (devcons).
> am i missing something?

if devmnt is involved, devcons is not.
it is some 9P server mounted on /dev/cons,
not the kernel's devcons.

russ