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#ifndef _SYS_LINUX_CONDVAR_H
#define _SYS_LINUX_CONDVAR_H
#ifdef __cplusplus
extern "C" {
#endif
#include <linux/wait.h>
/* The kcondvar_t struct is protected by mutex taken externally before
* calling any of the wait/signal funs, and passed into the wait funs.
*/
#define CV_MAGIC 0x346545f4
#define CV_POISON 0x95
typedef struct {
int cv_magic;
char *cv_name;
wait_queue_head_t cv_event;
atomic_t cv_waiters;
kmutex_t *cv_mutex; /* only for verification purposes */
} kcondvar_t;
typedef enum { CV_DEFAULT=0, CV_DRIVER } kcv_type_t;
static __inline__ void
cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg)
{
BUG_ON(cvp == NULL);
BUG_ON(type != CV_DEFAULT);
BUG_ON(arg != NULL);
cvp->cv_magic = CV_MAGIC;
init_waitqueue_head(&cvp->cv_event);
atomic_set(&cvp->cv_waiters, 0);
cvp->cv_mutex = NULL;
cvp->cv_name = NULL;
if (name) {
cvp->cv_name = kmalloc(strlen(name) + 1, GFP_KERNEL);
if (cvp->cv_name)
strcpy(cvp->cv_name, name);
}
}
static __inline__ void
cv_destroy(kcondvar_t *cvp)
{
BUG_ON(cvp == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
BUG_ON(atomic_read(&cvp->cv_waiters) != 0);
BUG_ON(waitqueue_active(&cvp->cv_event));
if (cvp->cv_name)
kfree(cvp->cv_name);
memset(cvp, CV_POISON, sizeof(*cvp));
}
static __inline__ void
cv_wait(kcondvar_t *cvp, kmutex_t *mtx)
{
DEFINE_WAIT(wait);
int flag = 1;
BUG_ON(cvp == NULL || mtx == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
BUG_ON(!mutex_owned(mtx));
if (cvp->cv_mutex == NULL)
cvp->cv_mutex = mtx;
/* Ensure the same mutex is used by all callers */
BUG_ON(cvp->cv_mutex != mtx);
for (;;) {
prepare_to_wait_exclusive(&cvp->cv_event, &wait,
TASK_INTERRUPTIBLE);
/* Must occur after we are added to the list but only once */
if (flag) {
atomic_inc(&cvp->cv_waiters);
flag = 0;
}
/* XXX - The correct thing to do here may be to wake up and
* force the caller to handle the signal. Spurious wakeups
* should already be safely handled by the caller. */
if (signal_pending(current))
flush_signals(current);
/* Mutex should be dropped after prepare_to_wait() this
* ensures we're linked in to the waiters list and avoids the
* race where 'cvp->cv_waiters > 0' but the list is empty. */
mutex_exit(mtx);
schedule();
mutex_enter(mtx);
/* XXX - The correct thing to do here may be to wake up and
* force the caller to handle the signal. Spurious wakeups
* should already be safely handled by the caller. */
if (signal_pending(current))
continue;
break;
}
atomic_dec(&cvp->cv_waiters);
finish_wait(&cvp->cv_event, &wait);
}
/* 'expire_time' argument is an absolute wall clock time in jiffies.
* Return value is time left (expire_time - now) or -1 if timeout occurred.
*/
static __inline__ clock_t
cv_timedwait(kcondvar_t *cvp, kmutex_t *mtx, clock_t expire_time)
{
DEFINE_WAIT(wait);
clock_t time_left;
int flag = 1;
BUG_ON(cvp == NULL || mtx == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
BUG_ON(!mutex_owned(mtx));
if (cvp->cv_mutex == NULL)
cvp->cv_mutex = mtx;
/* XXX - Does not handle jiffie wrap properly */
time_left = expire_time - jiffies;
if (time_left <= 0)
return -1;
/* Ensure the same mutex is used by all callers */
BUG_ON(cvp->cv_mutex != mtx);
for (;;) {
prepare_to_wait_exclusive(&cvp->cv_event, &wait,
TASK_INTERRUPTIBLE);
if (flag) {
atomic_inc(&cvp->cv_waiters);
flag = 0;
}
/* XXX - The correct thing to do here may be to wake up and
* force the caller to handle the signal. Spurious wakeups
* should already be safely handled by the caller. */
if (signal_pending(current))
flush_signals(current);
/* Mutex should be dropped after prepare_to_wait() this
* ensures we're linked in to the waiters list and avoids the
* race where 'cvp->cv_waiters > 0' but the list is empty. */
mutex_exit(mtx);
time_left = schedule_timeout(time_left);
mutex_enter(mtx);
/* XXX - The correct thing to do here may be to wake up and
* force the caller to handle the signal. Spurious wakeups
* should already be safely handled by the caller. */
if (signal_pending(current)) {
if (time_left > 0)
continue;
flush_signals(current);
}
break;
}
atomic_dec(&cvp->cv_waiters);
finish_wait(&cvp->cv_event, &wait);
return (time_left > 0 ? time_left : -1);
}
static __inline__ void
cv_signal(kcondvar_t *cvp)
{
BUG_ON(cvp == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
/* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
* waiter will be set runable with each call to wake_up().
* Additionally wake_up() holds a spin_lock assoicated with
* the wait queue to ensure we don't race waking up processes. */
if (atomic_read(&cvp->cv_waiters) > 0)
wake_up(&cvp->cv_event);
}
static __inline__ void
cv_broadcast(kcondvar_t *cvp)
{
BUG_ON(cvp == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
/* Wake_up_all() will wake up all waiters even those which
* have the WQ_FLAG_EXCLUSIVE flag set. */
if (atomic_read(&cvp->cv_waiters) > 0)
wake_up_all(&cvp->cv_event);
}
#endif /* _SYS_LINUX_CONDVAR_H */
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