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ntsync: Introduce alertable waits.

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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@codeweavers.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20241213193511.457338-16-zfigura@codeweavers.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Elizabeth Figura 2024-12-13 13:34:56 -06:00 committed by Greg Kroah-Hartman
parent e864071a63
commit a138179a59
2 changed files with 63 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

70
drivers/misc/ntsync.c
View File

@ -869,22 +869,29 @@ 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;
@ -894,7 +901,7 @@ 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]);
@ -944,10 +951,10 @@ 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)))
@ -957,9 +964,13 @@ 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;
@ -968,9 +979,15 @@ 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)
@ -987,7 +1004,7 @@ 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;
@ -1047,6 +1064,14 @@ 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 */
@ -1054,6 +1079,21 @@ 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);
@ -1079,6 +1119,18 @@ 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;

3
include/uapi/linux/ntsync.h
View File

@ -34,7 +34,8 @@ struct ntsync_wait_args {
__u32 index;
__u32 flags;
__u32 owner;
__u32 pad[2];
__u32 alert;
__u32 pad;
};
#define NTSYNC_MAX_WAIT_COUNT 64