cvs commit: src/sys/kern kern_lockf.c

Doug Rabson dfr at
Wed Mar 19 01:59:05 PDT 2008

On 19 Mar 2008, at 07:13, Jeff Roberson wrote:

> jeff        2008-03-19 07:13:24 UTC
>  FreeBSD src repository
>  Modified files:
>    sys/kern             kern_lockf.c
>  Log:
>   - Fix the last of the threading bugs that were introduced as far  
> back as
>     1.38 in 2001.  Break out of the FOREACH_THREAD_IN_PROC loop when  
> we've
>     discovered a new proc in the chain.
>   - Increment i and check for maxlockdepth once per matching process  
> not
>     once per thread.  This didn't properly terminate the loop before.
>   - Fix a bug which has existed potentially since rev 1.1.   
> waitblock->lf_next
>     can be NULL when a thread has been woken-up but not yet  
> scheduled.  Check
>     for this condition rather than blindly dereferencing.
>  Found by:       libMicro
>  Revision  Changes    Path
>  1.59      +12 -6     src/sys/kern/kern_lockf.c

I have completely removed all this proc tomfoolery in my perforce  
branch and have replaced it with a real deadlock detection system  
instead of this horrible code. Apart from anything else, the existing  
code has serious locking problems - if the deadlock loop spans two or  
more vnodes, it doesn't lock any but the first one.

I should have a patch ready for review (along with the new kernel NFS  
lock manager) towards the end of this week and I hope to get the thing  
into -current some time next week.

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