Pthread spin locks

[Daniel Eischen]

On Mon, 19 Mar 2007, Joerg Sonnenberger wrote:

> On Mon, Mar 19, 2007 at 02:04:58PM -0400, Daniel Eischen wrote:
>> No, especially if the threads hold other locks.
>> I have no idea why POSIX added spinlocks.  I don't
>> see why anyone would want to use them.
>
> Given that it is part of the realtime extensions, it makes sense. On
> those systems you generally also have policies for scheduler control
> like CPU affinity, which can make the starvation impossible.

PTHREAD_PRIO_PROTECT and PTHREAD_PRIO_INHERIT

POSIX doesn't seem to have specified APIs for
scheduler affinity and has said that the behavior
of threads in scheduling domains > 1 is implementation
defined.  So it is somewhat surprising to me that
spinlocks were added.

It also assumes that the implementation of non-spin mutexes
is inefficient which is not necessarily the case.  It is
certainly possible for the implementation to use adaptive
mutexes which spin for a bit before sleeping.

-- 
DE