Date: Thu, 12 Oct 2000 21:44:46 -0700 From: Jason Evans <jasone@canonware.com> To: Terry Lambert <tlambert@primenet.com> Cc: Alfred Perlstein <bright@wintelcom.net>, Chuck Paterson <cp@bsdi.com>, Mike Smith <msmith@FreeBSD.ORG>, arch@FreeBSD.ORG Subject: Re: we need atomic_t Message-ID: <20001012214446.H11949@canonware.com> In-Reply-To: <200010130251.TAA03945@usr05.primenet.com>; from tlambert@primenet.com on Fri, Oct 13, 2000 at 02:51:31AM %2B0000 References: <20001012192229.F272@fw.wintelcom.net> <200010130251.TAA03945@usr05.primenet.com>
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On Fri, Oct 13, 2000 at 02:51:31AM +0000, Terry Lambert wrote:
> > The reason for atomic_init/destroy is to intialize mutexes if they
> > are needed on the arch. Basically atomic64_t on 32bit arches would
> > be a struct with a 64bit value and a mutex to protect it.
>
> Tee hee hee.
>
> How do I initialize the mutex that protects the mutex?
>
> I think it's time to learn from the POSIX threads mutex
> implementation, wherein it is impossible to statically
> initialize a mutex, and to obtain that appearance, you
> have to trick the loader into doing the work using the
> section which is used for the construction of virtual
> base classes in C++ (see my modifications to the STL, as
> applied to the Moscow Center for Supercomuting Activites
> STL, which is the most up to date STL available).
Here's one of Butenhof's example programs, which uses POSIX threads:
-------------------------------------------------------------------------
/*
* mutex_static.c
*
* Demonstrate static initialization of a mutex.
*/
#include <pthread.h>
/*
* Declare a structure, with a mutex, statically initialized. This is the
* same as using pthread_mutex_init, with the default attributes.
*/
typedef struct my_struct_tag {
pthread_mutex_t mutex; /* Protects access to value */
int value; /* Access protected by mutex */
} my_struct_t;
my_struct_t data = {PTHREAD_MUTEX_INITIALIZER, 0};
int main (int argc, char *argv[])
{
return 0;
}
-------------------------------------------------------------------------
That looks like static mutex initialization to me. =)
Jason
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