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Adjust the condition variables to simply sleep uninteruptibly.

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This way we don't have to contend with superious wakeups which
it appears ZFS is not so careful to handle anyway.  So this is
probably for the best.


git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@70 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c
This commit is contained in:
behlendo 2008-04-11 22:49:48 +00:00
parent 115aed0dd8
commit 12ea923056
1 changed files with 31 additions and 68 deletions
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99
include/sys/condvar.h
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@ -20,6 +20,7 @@ typedef struct {
wait_queue_head_t cv_event;
atomic_t cv_waiters;
kmutex_t *cv_mutex; /* only for verification purposes */
spinlock_t cv_lock;
} kcondvar_t;
typedef enum { CV_DEFAULT=0, CV_DRIVER } kcv_type_t;
@ -33,13 +34,14 @@ cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg)
cvp->cv_magic = CV_MAGIC;
init_waitqueue_head(&cvp->cv_event);
spin_lock_init(&cvp->cv_lock);
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)
cvp->cv_name = kmalloc(strlen(name) + 1, GFP_KERNEL);
if (cvp->cv_name)
strcpy(cvp->cv_name, name);
}
}
@ -48,6 +50,7 @@ static __inline__ void
cv_destroy(kcondvar_t *cvp)
{
BUG_ON(cvp == NULL);
spin_lock(&cvp->cv_lock);
BUG_ON(cvp->cv_magic != CV_MAGIC);
BUG_ON(atomic_read(&cvp->cv_waiters) != 0);
BUG_ON(waitqueue_active(&cvp->cv_event));
@ -56,15 +59,16 @@ cv_destroy(kcondvar_t *cvp)
kfree(cvp->cv_name);
memset(cvp, CV_POISON, sizeof(*cvp));
spin_unlock(&cvp->cv_lock);
}
static __inline__ void
cv_wait(kcondvar_t *cvp, kmutex_t *mtx)
{
DEFINE_WAIT(wait);
int flag = 1;
BUG_ON(cvp == NULL || mtx == NULL);
spin_lock(&cvp->cv_lock);
BUG_ON(cvp->cv_magic != CV_MAGIC);
BUG_ON(!mutex_owned(mtx));
@ -73,37 +77,18 @@ cv_wait(kcondvar_t *cvp, kmutex_t *mtx)
/* Ensure the same mutex is used by all callers */
BUG_ON(cvp->cv_mutex != mtx);
spin_unlock(&cvp->cv_lock);
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;
}
prepare_to_wait_exclusive(&cvp->cv_event, &wait,
TASK_UNINTERRUPTIBLE);
atomic_inc(&cvp->cv_waiters);
/* 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;
}
/* 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);
atomic_dec(&cvp->cv_waiters);
finish_wait(&cvp->cv_event, &wait);
@ -117,56 +102,34 @@ 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);
spin_lock(&cvp->cv_lock);
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);
spin_unlock(&cvp->cv_lock);
/* 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);
prepare_to_wait_exclusive(&cvp->cv_event, &wait,
TASK_UNINTERRUPTIBLE);
atomic_inc(&cvp->cv_waiters);
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;
}
/* 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);
atomic_dec(&cvp->cv_waiters);
finish_wait(&cvp->cv_event, &wait);