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Re: Replace lockmgr for vnodes

On Sun, Jan 27, 2008 at 10:40:11PM +0100, Reinoud Zandijk wrote:
> Dear folks,
> On Sat, Jan 26, 2008 at 05:57:50PM +0000, Andrew Doran wrote:
> > > 3) I think it'd be nice if we could retain something akin to 
> > > lockmgr_printinfo(). I realize that our locking is now such that we need 
> > > to print more than just one big heavy lock. However being able to figure 
> > > out what's up/broken with locks can help. :-)
> > 
> > We have 'show lock' from ddb. I'll see about providing a replacement.

> Debugging on deadlock detection then becomes printing out the locks and 
> their claim and release points.
> Could a kmutex be given a kind of `timeout' value? i.e. if it hasn't been 
> exited after the specified time it is considered a deadlock? Say a minute 
> or so as default?
> comments?

Do all of the places that try to lock a kmutex always check return values?  
The older locking primitives, such as vnode locks, often were called in
places that didn't cope with getting a return error code. Many times that
means they didn't bother to check. :-)

While you're probably right that something's wrong if we spend a minute 
waiting for a mutex, I'm not sure what we can do about it. I think we'll 
run into problems just adding deadlock detection/resolution externally; 
the code that grabs the locks needs to be able to cope with retry/deadlock 

Take care,


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