NT waits can optionally be made "alertable". This is a special channel for
thread wakeup that is mildly similar to SIGIO. A thread has an internal single
bit of "alerted" state, and if a thread is alerted while an alertable wait, the
wait will return a special value, consume the "alerted" state, and will not
consume any of its objects.
Alerts are implemented using events; the user-space NT emulator is expected to
create an internal ntsync event for each thread and pass that event to wait
functions.
Signed-off-by: Elizabeth Figura <zfigura@xxxxxxxxxxxxxxx>
---
drivers/misc/ntsync.c | 70 ++++++++++++++++++++++++++++++++-----
include/uapi/linux/ntsync.h | 3 +-
2 files changed, 63 insertions(+), 10 deletions(-)
diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index a11fe2469841..87a24798a5c7 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -885,22 +885,29 @@ static int setup_wait(struct ntsync_device *dev,
const struct ntsync_wait_args *args, bool all,
struct ntsync_q **ret_q)
{
+ int fds[NTSYNC_MAX_WAIT_COUNT + 1];
const __u32 count = args->count;
- int fds[NTSYNC_MAX_WAIT_COUNT];
struct ntsync_q *q;
+ __u32 total_count;
__u32 i, j;
- if (args->pad[0] || args->pad[1] || (args->flags & ~NTSYNC_WAIT_REALTIME))
+ if (args->pad || (args->flags & ~NTSYNC_WAIT_REALTIME))
return -EINVAL;
if (args->count > NTSYNC_MAX_WAIT_COUNT)
return -EINVAL;
+ total_count = count;
+ if (args->alert)
+ total_count++;
+
if (copy_from_user(fds, u64_to_user_ptr(args->objs),
array_size(count, sizeof(*fds))))
return -EFAULT;
+ if (args->alert)
+ fds[count] = args->alert;
- q = kmalloc(struct_size(q, entries, count), GFP_KERNEL);
+ q = kmalloc(struct_size(q, entries, total_count), GFP_KERNEL);
if (!q)
return -ENOMEM;
q->task = current;
@@ -910,7 +917,7 @@ static int setup_wait(struct ntsync_device *dev,
q->ownerdead = false;
q->count = count;
- for (i = 0; i < count; i++) {
+ for (i = 0; i < total_count; i++) {
struct ntsync_q_entry *entry = &q->entries[i];
struct ntsync_obj *obj = get_obj(dev, fds[i]);
@@ -960,10 +967,10 @@ static void try_wake_any_obj(struct ntsync_obj *obj)
static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
{
struct ntsync_wait_args args;
+ __u32 i, total_count;
struct ntsync_q *q;
int signaled;
bool all;
- __u32 i;
int ret;
if (copy_from_user(&args, argp, sizeof(args)))
@@ -973,9 +980,13 @@ static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
if (ret < 0)
return ret;
+ total_count = args.count;
+ if (args.alert)
+ total_count++;
+
/* queue ourselves */
- for (i = 0; i < args.count; i++) {
+ for (i = 0; i < total_count; i++) {
struct ntsync_q_entry *entry = &q->entries[i];
struct ntsync_obj *obj = entry->obj;
@@ -984,9 +995,15 @@ static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
ntsync_unlock_obj(dev, obj, all);
}
- /* check if we are already signaled */
+ /*
+ * Check if we are already signaled.
+ *
+ * Note that the API requires that normal objects are checked before
+ * the alert event. Hence we queue the alert event last, and check
+ * objects in order.
+ */
- for (i = 0; i < args.count; i++) {
+ for (i = 0; i < total_count; i++) {
struct ntsync_obj *obj = q->entries[i].obj;
if (atomic_read(&q->signaled) != -1)
@@ -1003,7 +1020,7 @@ static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
/* and finally, unqueue */
- for (i = 0; i < args.count; i++) {
+ for (i = 0; i < total_count; i++) {
struct ntsync_q_entry *entry = &q->entries[i];
struct ntsync_obj *obj = entry->obj;
@@ -1063,6 +1080,14 @@ static int ntsync_wait_all(struct ntsync_device *dev, void __user *argp)
*/
list_add_tail(&entry->node, &obj->all_waiters);
}
+ if (args.alert) {
+ struct ntsync_q_entry *entry = &q->entries[args.count];
+ struct ntsync_obj *obj = entry->obj;
+
+ dev_lock_obj(dev, obj);
+ list_add_tail(&entry->node, &obj->any_waiters);
+ dev_unlock_obj(dev, obj);
+ }
/* check if we are already signaled */
@@ -1070,6 +1095,21 @@ static int ntsync_wait_all(struct ntsync_device *dev, void __user *argp)
mutex_unlock(&dev->wait_all_lock);
+ /*
+ * Check if the alert event is signaled, making sure to do so only
+ * after checking if the other objects are signaled.
+ */
+
+ if (args.alert) {
+ struct ntsync_obj *obj = q->entries[args.count].obj;
+
+ if (atomic_read(&q->signaled) == -1) {
+ bool all = ntsync_lock_obj(dev, obj);
+ try_wake_any_obj(obj);
+ ntsync_unlock_obj(dev, obj, all);
+ }
+ }
+
/* sleep */
ret = ntsync_schedule(q, &args);
@@ -1095,6 +1135,18 @@ static int ntsync_wait_all(struct ntsync_device *dev, void __user *argp)
mutex_unlock(&dev->wait_all_lock);
+ if (args.alert) {
+ struct ntsync_q_entry *entry = &q->entries[args.count];
+ struct ntsync_obj *obj = entry->obj;
+ bool all;
+
+ all = ntsync_lock_obj(dev, obj);
+ list_del(&entry->node);
+ ntsync_unlock_obj(dev, obj, all);
+
+ put_obj(obj);
+ }
+
signaled = atomic_read(&q->signaled);
if (signaled != -1) {
struct ntsync_wait_args __user *user_args = argp;
diff --git a/include/uapi/linux/ntsync.h b/include/uapi/linux/ntsync.h
index 74abeba832f7..4a8095a3fc34 100644
--- a/include/uapi/linux/ntsync.h
+++ b/include/uapi/linux/ntsync.h
@@ -37,7 +37,8 @@ struct ntsync_wait_args {
__u32 index;
__u32 flags;
__u32 owner;
- __u32 pad[2];
+ __u32 alert;
+ __u32 pad;
};
#define NTSYNC_MAX_WAIT_COUNT 64
--
2.43.0
