pthread_lock

[Mandeep Sandhu]

On Tue, Mar 5, 2013 at 11:32 AM,  <Valdis.Kletnieks at vt.edu> wrote:
> On Tue, 05 Mar 2013 11:02:45 +0530, Mandeep Sandhu said:
>
>> next schedule. I think the waiting threads (processes) will moved from
>> the wait queue to the run queue from where they will be scheduled to
>> run.
>
> For bonus points, read source code and/or comments and figure out what
> Linux does to prevent the 'thundering herd' problem (consider 100 threads
> all waiting on the same mutex - if you blindly wake all 100 up, you'll schedule
> them all, the first will find the mutex available and then re-take it, and
> then the next 99 will get run only to find it contended and go back to
> sleep.  So figure out what Linux does in that case. :)

Googling around, I found the 'thundering herd' being mentioned in
relation to threads waiting on sockets using the accept() sys call.
Are wait's on mutex's also plagued by the same issue? I guess it is,
though what sys call would be used in this case?

Thanks,
-mandeep