Re: [CHECKER] potential deadlocks

[Dawson Engler <engler@csl.stanford.edu>]

> Dawson Engler <engler@csl.stanford.edu> wrote:
> >
> > BTW, are there known deadlocks (harmless or otherwise)?  Debugging
> > the checker is a bit hard since false negatives are silent...
> 
> Known deadlocks tend to get fixed.  But I am surprised that you did not
> encounter more of them.

;-)

I sent out a *very* small subset of the checker's output.  There are
hundreds of messages.  I wanted to check on validity before flooding
people.


> btw, the filesystem transaction operations can be treated as sleeping locks. 
> So for ext3, journal_start()/journal_stop() may, for lock-ranking purposes,
> be treated in the same way as taking and releasing a per-superblock
> semaphore.  Other filesystems probably have similar restrictions.
> 
> Other such "hidden" sleeping locks are lock_sock() and wait_on_inode().  The
> latter is rather messy because there is no clear API function which sets
> I_LOCK.
> 
> And pte_chain_lock() is a custom spinlock.

Good deal.  Thanks for the pointers, I was missing all of these besides
lock_sock.

One nice thing is that the race detector has been OK at pointing out
when a locking function is missing from our list.

Dawson