From 2c391d57d1393cd46bf8bab08232ddc3dd32d5e5 Mon Sep 17 00:00:00 2001 From: Elizabeth Figura Date: Sun, 19 May 2024 15:24:39 -0500 Subject: ntsync: Introduce alertable waits. 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 --- drivers/misc/ntsync.c | 70 ++++++++++++++++++++++++++++++++----- include/uapi/linux/ntsync.h | 3 +- 2 files changed, 63 insertions(+), 10 deletions(-) --- a/drivers/misc/ntsync.c +++ b/drivers/misc/ntsync.c @@ -884,22 +884,29 @@ static int setup_wait(struct ntsync_devi 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; @@ -909,7 +916,7 @@ static int setup_wait(struct ntsync_devi 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]); @@ -959,10 +966,10 @@ static void try_wake_any_obj(struct ntsy 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))) @@ -972,9 +979,13 @@ static int ntsync_wait_any(struct ntsync 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; @@ -983,9 +994,15 @@ static int ntsync_wait_any(struct ntsync 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) @@ -1002,7 +1019,7 @@ static int ntsync_wait_any(struct ntsync /* 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; @@ -1062,6 +1079,14 @@ static int ntsync_wait_all(struct ntsync */ 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 */ @@ -1069,6 +1094,21 @@ static int ntsync_wait_all(struct ntsync 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); @@ -1094,6 +1134,18 @@ static int ntsync_wait_all(struct ntsync 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; --- 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