Re: [RFC PATCH 1/2] ipc: introduce obtaining a lockless ipc object

[Mike Galbraith]

On Sat, 2013-03-02 at 21:18 -0500, Rik van Riel wrote: 
> On 03/01/2013 11:32 PM, Michel Lespinasse wrote:
> 
> > I think it may be nicer to take the rcu read lock at the call site
> > rather than in ipc_obtain_object(), to make the rcu read lock/unlock
> > sites pair up more nicely. Either that or make an inline
> > ipc_release_object function that pairs up with ipc_obtain_object() and
> > just does an rcu_read_unlock().
> 
> I started on a patch series to untangle the IPC locking, so
> it will be a little more readable, and easier to maintain.
> 
> It is a slower approach than Davidlohr's, as in, it will take
> a little longer to put a patch series together, but I hope it
> will be easier to debug...
> 
> I hope to post a first iteration of the series by the middle
> of next week.

Goody, I'll be watching out for it.  I have a big box rt user who uses
semaphores in their very tight constraint application.  While they're
using them carefully, I saw a trace where contention cost vs jitter
budget was a bit too high for comfort, and semctl/semop collision.

-Mike

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/