Andrew Morton wrote:

>Manfred Spraul <manfred@colorfullife.com> wrote:
>  
>
>>__unhash_process acquires the dcache_lock while holding the 
>>tasklist_lock for writing. This can deadlock. While trying to fix that 
>>race, I found further races with proc_dentry.
>>The attached patch (hopefully) fixes all these races.
>>
>>Changes:
>>- fs/proc/base.c assumed that p->pid is reset to 0 during exit. This is 
>>not the case anymore. I now look at the count of the pid structure for 
>>PIDTYPE_PID.
>>- pid_delete_dentry and pid_revalidate removed. The implementation 
>>didn't work, and noone complained.
>>- only d_add the new proc entry if the task is still valid: d_add+d_drop 
>>is a race, if a lookup happens between both calls.
>>- add a new spinlock that protects proc_dentry.
>>    
>>
>
>Did you send the correct patch?
>  
>
Yes, but my diff script was incomplete :-(

>kernel/exit.c: In function `release_task':
>kernel/exit.c:59: warning: implicit declaration of function `proc_pid_unhash'
>
Missing updates to <linux/proc_fs.h>

>kernel/exit.c:59: warning: assignment makes pointer from integer without a cast
>kernel/exit.c:86: warning: implicit declaration of function `proc_pid_flush'
>kernel/exit.c: In function `unhash_process':
>kernel/exit.c:95: warning: `proc_dentry' might be used uninitialized in this function
>
And this one is a fatal error: proc_dentry remained uninitialized, and 
that crashes during smp boot.

New patch attached.
Changelog unchanged.

--
    Manfred