RE: NULL pointer in proc_pid_stat -- oops.

[Andrew Reiter]

Oops, I was getting confused since proc_pid_status() is directly above
proc_pid_stat() in fs/proc/array.c, so I misinterpreted some of the
asm<-->C translation and was stating we were dying in task_name().
Sorry for the confusion.  Will apply Ricky's patch for now as a work
around as it seems fine to me for the moment.

Thanks for the help... 

Cheers,
Andrew

-----Original Message-----
From: OGAWA Hirofumi [mailto:hirofumi@xxxxxxxxxxxxxxxxxx] 
Sent: Sunday, March 28, 2004 9:00 AM
To: Andrew Reiter
Cc: linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: NULL pointer in proc_pid_stat -- oops.


"Andrew Reiter" <areiter@xxxxxxxxxxxxxx> writes:

> 0x000004d4 <proc_pid_stat+124>: test   %ecx,%ecx
> 0x000004d6 <proc_pid_stat+126>: je     0x510 <proc_pid_stat+184>
> 0x000004d8 <proc_pid_stat+128>: mov    0x98(%ecx),%eax
> 0x000004de <proc_pid_stat+134>: mov    %eax,0x20(%esp,1)
> 0x000004e2 <proc_pid_stat+138>: mov    0x4(%ecx),%edx
> 0x000004e5 <proc_pid_stat+141>: movswl 0x64(%edx),%eax
> 0x000004e9 <proc_pid_stat+145>: movswl 0x66(%edx),%edx
> 0x000004ed <proc_pid_stat+149>: shl    $0x14,%eax
> 0x000004f0 <proc_pid_stat+152>: or     %edx,%eax
> 0x000004f2 <proc_pid_stat+154>: add    0x8(%ecx),%eax
> 
> And from the oops trace output (that is attached), we can see that
%edx
> is 0x0; so we can easily see here why we're crashing at least.  After
> examining the C source, I see that we're dying in the call to
> task_name() (inline) from proc_pid_stat().

Looks like this problem is same with BSD acct Oops.

	if (task->tty) {
		tty_pgrp = task->tty->pgrp;
		tty_nr = new_encode_dev(tty_devnum(task->tty));
	}

Some place doesn't take the any lock for ->tty. I think we need to
take the lock for ->tty.
-- 
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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