Ok, used your code, and created some paired functions in OWLIB:
// ow_api.c
int OWLIB_can_init_start( void ) ;
void OWLIB_can_init_end( void ) ;
int OWLIB_can_access_start( void ) ;
void OWLIB_can_access_end( void ) ;
int OWLIB_can_finish_start( void ) ;
void OWLIB_can_finish_end( void ) ;
The gist of this is that all the mutexes and conditions variables are hidden
from the C api, and also they can be used by other programs.
Paul
The implementation is in modules/owlib/src/c/ow_api.c and looks like this:
/* code for SWIG and owcapi safe access */
/* Uses two mutexes, one for indevices, showing of there are valid 1-wire
adapters */
/* Second is paired with a condition variable to prevent "finish" when a "get"
or "put" is in progress */
/* Thanks to Geo Carncross for the implementation */
#include "owfs_config.h"
#include "ow.h"
/* ------- Globals ----------- */
#ifdef OW_MT
pthread_mutex_t init_mutex = PTHREAD_MUTEX_INITIALIZER ;
pthread_mutex_t access_mutex = PTHREAD_MUTEX_INITIALIZER ;
pthread_cond_t access_cond = PTHREAD_COND_INITIALIZER ;
#define INITLOCK pthread_mutex_lock( &init_mutex )
#define INITUNLOCK pthread_mutex_unlock( &init_mutex )
#define ACCESSLOCK pthread_mutex_lock( &access_mutex )
#define ACCESSUNLOCK pthread_mutex_unlock(&access_mutex )
#define ACCESSWAIT pthread_cond_wait( &access_cond, &access_mutex )
#define ACCESSSIGNAL pthread_cond_signal( &access_cond )
#else /* OW_MT */
#define INITLOCK
#define INITUNLOCK
#define ACCESSLOCK
#define ACCESSUNLOCK
#define ACCESSWAIT
#define ACCESSSIGNAL
#endif /* OW_MT */
int access_num = 0 ;
/* Returns 0 if ok, else 1 */
/* MUST BE PAIRED with OWLIB_can_init_end() */
int OWLIB_can_init_start( void ) {
#ifdef OW_MT
#ifdef __UCLIBC__
if ( INITLOCK == EINVAL ) { /* Not initialized */
pthread_mutex_init(&init_mutex, pmattr);
pthread_mutex_init(&access_mutex, pmattr);
INITLOCK ;
}
#else /* UCLIBC */
INITLOCK ;
#endif /* UCLIBC */
#endif /* OW_MT */
return indevices > 0 ;
}
void OWLIB_can_init_end( void ) {
INITUNLOCK ;
}
/* Returns 0 if ok, else 1 */
/* MUST BE PAIRED with OWLIB_can_access_end() */
int OWLIB_can_access_start( void ) {
int ret ;
ACCESSLOCK ;
access_num++ ;
ACCESSUNLOCK ;
INITLOCK ;
ret = (indevices == 0) ;
INITUNLOCK ;
return ret ;
}
void OWLIB_can_access_end( void ) {
ACCESSLOCK ;
access_num-- ;
ACCESSSIGNAL ;
ACCESSUNLOCK ;
}
/* Returns 0 always */
/* MUST BE PAIRED with OWLIB_can_finish_end() */
int OWLIB_can_finish_start( void ) {
ACCESSLOCK ;
while ( access_num > 0 ) ACCESSWAIT;
INITLOCK ;
return 0 ; /* just for symetry */
}
void OWLIB_can_finish_end( void ) {
INITUNLOCK ;
ACCESSUNLOCK ;
}
On Monday 17 October 2005 10:24 am, Geo Carncross wrote:
> A mutual exclusion device is necessary.
>
> OW_get, OW_put, and OW_finish all lock the common mutex.
>
> If OW_get and OW_put /really can/ be used simultaneously, then a
> condition is required:
>
>
> in OW_get and OW_put:
>
> LOCK(mutex);
> level++;
> UNLOCK(mutex);
> { real code }
> LOCK(mutex);
> level--;
> SIGNAL(cond);
> UNLOCK(mutex);
>
>
> and in OW_finish:
>
> LOCK(mutex);
> while (level > 0) COND(cond,mutex);
> { destroy interface safely now }
> UNLOCK(mutex);
>
>
> in pthreads this is:
>
> pthread_cond_t cond;
> pthread_mutex_t mutex;
>
> #define COND(q,p) pthread_cond_wait(&q,&p)
> #define SIGNAL(q) pthread_cond_signal(&q)
> #define LOCK(q) pthread_mutex_lock(&q)
> #define UNLOCK(q) pthread_mutex_unlock(&q)
>
>
> NOTE: this is NOT the same mutex as you're using for acessing indev
> (capi_mutex) - but a different one JUST for this cond variable.
>
>
> BY THE WAY, shouldn't these things be static? Is there really a reason
> user programs should have access to it?
>
> On Sun, 2005-10-16 at 22:57 -0400, Paul Alfille wrote:
> > Added the same protection for the SWIG prototype (owperl, owpython,
> > owphp).
> >
> > It occurs to me that it is possible that a "OW_finish" could be called
> > while an OW_get or OW_put is in progress -- could be messy since the
> > adapters would be disappearing while being used. I'll have to get out the
> > old textbook to figure the proper flag for this one -- a semaphore?
> >
> > Paul
> >
> > On Sunday 16 October 2005 01:33 am, Paul Alfille wrote:
> > > Ok uploaded some OWCAPI changes.
> > >
> > > 1. I've put in your char** mode. I'm really starting to warm up to it.
> > >
> > > 2. Protection against multiple "init"s, no "init"s, simultaneous
> > > "init"s...
> > >
> > > Paul
> >
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