Re: Proposed fix for i_sem deadlock in devfs in 2.4.2x kernel

[Andrey Borzenkov]

> devfs_d_revalidate_wait()
> {
>	...
>	read_lock(...)
>	...
>	add_wait_queue(&lookup_info->wait_queue, ...);
>	read_unlock(...)
>	up(&dir->i_sem);		/* add for this proposed fix */

this can be called both with and without i_sem held. i_sem is held
for directory modifications but not for simple lookups. Is it correct
to increase i_sem count above 1? Note, it will be done by every
task so it may screw up locking completely.

Look at <http://marc.theaimsgroup.com/?l=linux-kernel&m=105233420622539&w=2> for alternative fix. 

-andrey

>	schedule();
>	down(&dir->i_sem);	/* add for this proposed fix */
>	...
>}