Re: [Starpu-devel] Drivers, schedulers: where should sched_mutex be locked ?

[Samuel Thibault <samuel.thibault@ens-lyon.org>]

Cyril Roelandt, le Wed 27 Jun 2012 16:43:39 +0200, a écrit :
> The attached patch locks sched_mutex at two different places, rather
> than once in the driver:
> - in _starpu_pop_task(), before calling _starpu_pop_local_task();
> - in the driver, before calling _starpu_block_worker().

That won't fly, because what is needed is that the driver decision to
sleep has to be atomic with the scheduler discover of no available task.
Failing that, a driver can go to sleep just after the scheduler has
pushed a task to be executed.

Composition is nice on the paper, but locks screw it up most of the time
:)

Samuel