Subj : Re: recursive mutexes
To   : comp.programming.threads
From : Casper H.S. Dik
Date : Wed May 18 2005 08:22 pm

"Uenal Mutlu" <520001085531-0001@t-online.de> writes:

>Do you know or believe that your OS makes no use recursive mutexes?
>I personally cannot believe that any complex system of nowadays like an
>OS or any server application can be developed without recursive mutices.

The Solaris kernel does not use recursive mutexes; that, I think,
sufficiently discredits your "belief".

The Solaris runtime does implement recursive mutexes, as
part of the POSIX thread library/UI threads (they're the
same).  I know of one use in the Solaris runtime, but
only because we've decided to use the same lock
for flockfile() as we use for ordinary stdio
calls.  But there's no particular reason that it
has to be implemented that way.

(The recursive mutex is only slightly more expensive
than the ordinary mutex as the unlock path is more
expensive)

Casper
-- 
Expressed in this posting are my opinions.  They are in no way related
to opinions held by my employer, Sun Microsystems.
Statements on Sun products included here are not gospel and may
be fiction rather than truth.

.