Subject: Re: Lock benchmarks
To: None <>
From: Jason R Thorpe <>
List: tech-kern
Date: 09/18/2002 15:26:03
On Thu, Sep 19, 2002 at 08:33:18AM +1200, Gregory McGarry wrote:

 > > 	1. In a RAS locking scheme, you only ever want to provide
 > > 	   or use the "lock_try" version.  This is because if the
 > > 	   lock is held, know either: (a) you need to context
 > > 	   switch, (b) you need to croak (deadlock).  If you spin
 > > 	   around, then you're just consuming cpu time, and might
 > > 	   deadlock if your threads aren't being timesliced against
 > > 	   each other.
 > Yep.  And the pthread library currently works like that.

My point was that you don't need to provide the looping version of
__ras_simple_lock(), only __ras_simple_lock_try().

...and, actually, there is one place where __cpu_simple_lock() is used
in libpthread: pthread_spin_lock().

That function should be changed to use a loop around __cpu_simple_lock_try()
and detect deadlock and return the EDEADLK error.

        -- Jason R. Thorpe <>