Re: + sched-use-tasklet-to-call-balancing.patch added to -mm tree

[Christoph Lameter <clameter@sgi.com>]

On Tue, 7 Nov 2006, Siddha, Suresh B wrote:

> tasklet_schedule doesn't schedule if there is already one scheduled.

Right. 

/* Tasklets --- multithreaded analogue of BHs.

   Main feature differing them of generic softirqs: tasklet
   is running only on one CPU simultaneously.

   Main feature differing them of BHs: different tasklets
   may be run simultaneously on different CPUs.

   Properties:
   * If tasklet_schedule() is called, then tasklet is guaranteed
     to be executed on some cpu at least once after this.

^^^^ Crap. Not equivalent. Must be guaranteed to run on the same cpu.

   * If the tasklet is already scheduled, but its excecution is still not
     started, it will be executed only once.
   * If this tasklet is already running on another CPU (or schedule is called
     from tasklet itself), it is rescheduled for later.
   * Tasklet is strictly serialized wrt itself, but not
     wrt another tasklets. If client needs some intertask synchronization,
     he makes it with spinlocks.
 */