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Rewrite to remove dependence on rendezvous and its bizarre

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data structures.  Makes it easier to use pthreads too.
Still need to add code for non-pthreads systems.

Just a checkpoint to switch work to another machine.
This commit is contained in:
rsc 2004-09-17 00:38:29 +00:00
parent 984e353160
commit 06bb4ed20d
15 changed files with 205 additions and 218 deletions
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78
src/lib9/lock.c
View file

@ -2,52 +2,54 @@
#include <unistd.h>
#include <sys/time.h>
#include <sched.h>
#include <errno.h>
#include <libc.h>
int _ntas;
static int
_xtas(void *v)
{
int x;
static pthread_mutex_t initmutex = PTHREAD_MUTEX_INITIALIZER;
_ntas++;
x = _tas(v);
return x;
}
int
canlock(Lock *l)
static void
lockinit(Lock *lk)
{
return !_xtas(&l->val);
}
pthread_mutexattr_t attr;
void
unlock(Lock *l)
{
l->val = 0;
pthread_mutex_lock(&initmutex);
if(lk->init == 0){
pthread_mutexattr_init(&attr);
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_NORMAL);
pthread_mutex_init(&lk->mutex, &attr);
pthread_mutexattr_destroy(&attr);
lk->init = 1;
}
pthread_mutex_unlock(&initmutex);
}
void
lock(Lock *lk)
{
int i;
/* once fast */
if(!_xtas(&lk->val))
return;
/* a thousand times pretty fast */
for(i=0; i<1000; i++){
if(!_xtas(&lk->val))
return;
sched_yield();
}
/* now nice and slow */
for(i=0; i<1000; i++){
if(!_xtas(&lk->val))
return;
usleep(100*1000);
}
/* take your time */
while(_xtas(&lk->val))
usleep(1000*1000);
if(!lk->init)
lockinit(lk);
if(pthread_mutex_lock(&lk->mutex) != 0)
abort();
}
int
canlock(Lock *lk)
{
int r;
if(!lk->init)
lockinit(lk);
r = pthread_mutex_trylock(&lk->mutex);
if(r == 0)
return 1;
if(r == EBUSY)
return 0;
abort();
}
void
unlock(Lock *lk)
{
if(pthread_mutex_unlock(&lk->mutex) != 0)
abort();
}