*/
#include <linux/anon_inodes.h>
+#include <linux/atomic.h>
#include <linux/file.h>
#include <linux/fs.h>
+#include <linux/hrtimer.h>
+#include <linux/ktime.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/overflow.h>
+#include <linux/sched.h>
+#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <uapi/linux/ntsync.h>
*
* Both rely on struct file for reference counting. Individual
* ntsync_obj objects take a reference to the device when created.
+ * Wait operations take a reference to each object being waited on for
+ * the duration of the wait.
*/
struct ntsync_obj {
__u32 max;
} sem;
} u;
+
+ struct list_head any_waiters;
+};
+
+struct ntsync_q_entry {
+ struct list_head node;
+ struct ntsync_q *q;
+ struct ntsync_obj *obj;
+ __u32 index;
+};
+
+struct ntsync_q {
+ struct task_struct *task;
+
+ /*
+ * Protected via atomic_try_cmpxchg(). Only the thread that wins the
+ * compare-and-swap may actually change object states and wake this
+ * task.
+ */
+ atomic_t signaled;
+
+ __u32 count;
+ struct ntsync_q_entry entries[];
};
struct ntsync_device {
struct file *file;
};
+static void try_wake_any_sem(struct ntsync_obj *sem)
+{
+ struct ntsync_q_entry *entry;
+
+ lockdep_assert_held(&sem->lock);
+
+ list_for_each_entry(entry, &sem->any_waiters, node) {
+ struct ntsync_q *q = entry->q;
+ int signaled = -1;
+
+ if (!sem->u.sem.count)
+ break;
+
+ if (atomic_try_cmpxchg(&q->signaled, &signaled, entry->index)) {
+ sem->u.sem.count--;
+ wake_up_process(q->task);
+ }
+ }
+}
+
/*
* Actually change the semaphore state, returning -EOVERFLOW if it is made
* invalid.
spin_lock(&sem->lock);
prev_count = sem->u.sem.count;
- ret = release_sem_state(sem, args);
+ ret = post_sem_state(sem, args);
+ if (!ret)
+ try_wake_any_sem(sem);
spin_unlock(&sem->lock);
obj->dev = dev;
get_file(dev->file);
spin_lock_init(&obj->lock);
+ INIT_LIST_HEAD(&obj->any_waiters);
return obj;
}
return fd;
}
+static struct ntsync_obj *get_obj(struct ntsync_device *dev, int fd)
+{
+ struct file *file = fget(fd);
+ struct ntsync_obj *obj;
+
+ if (!file)
+ return NULL;
+
+ if (file->f_op != &ntsync_obj_fops) {
+ fput(file);
+ return NULL;
+ }
+
+ obj = file->private_data;
+ if (obj->dev != dev) {
+ fput(file);
+ return NULL;
+ }
+
+ return obj;
+}
+
+static void put_obj(struct ntsync_obj *obj)
+{
+ fput(obj->file);
+}
+
+static int ntsync_schedule(const struct ntsync_q *q, const struct ntsync_wait_args *args)
+{
+ ktime_t timeout = ns_to_ktime(args->timeout);
+ clockid_t clock = CLOCK_MONOTONIC;
+ ktime_t *timeout_ptr;
+ int ret = 0;
+
+ timeout_ptr = (args->timeout == U64_MAX ? NULL : &timeout);
+
+ if (args->flags & NTSYNC_WAIT_REALTIME)
+ clock = CLOCK_REALTIME;
+
+ do {
+ if (signal_pending(current)) {
+ ret = -ERESTARTSYS;
+ break;
+ }
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (atomic_read(&q->signaled) != -1) {
+ ret = 0;
+ break;
+ }
+ ret = schedule_hrtimeout_range_clock(timeout_ptr, 0, HRTIMER_MODE_ABS, clock);
+ } while (ret < 0);
+ __set_current_state(TASK_RUNNING);
+
+ return ret;
+}
+
+/*
+ * Allocate and initialize the ntsync_q structure, but do not queue us yet.
+ */
+static int setup_wait(struct ntsync_device *dev,
+ const struct ntsync_wait_args *args,
+ struct ntsync_q **ret_q)
+{
+ const __u32 count = args->count;
+ int fds[NTSYNC_MAX_WAIT_COUNT];
+ struct ntsync_q *q;
+ __u32 i, j;
+
+ if (args->pad[0] || args->pad[1] || args->pad[2] || (args->flags & ~NTSYNC_WAIT_REALTIME))
+ return -EINVAL;
+
+ if (args->count > NTSYNC_MAX_WAIT_COUNT)
+ return -EINVAL;
+
+ if (copy_from_user(fds, u64_to_user_ptr(args->objs),
+ array_size(count, sizeof(*fds))))
+ return -EFAULT;
+
+ q = kmalloc(struct_size(q, entries, count), GFP_KERNEL);
+ if (!q)
+ return -ENOMEM;
+ q->task = current;
+ atomic_set(&q->signaled, -1);
+ q->count = count;
+
+ for (i = 0; i < count; i++) {
+ struct ntsync_q_entry *entry = &q->entries[i];
+ struct ntsync_obj *obj = get_obj(dev, fds[i]);
+
+ if (!obj)
+ goto err;
+
+ entry->obj = obj;
+ entry->q = q;
+ entry->index = i;
+ }
+
+ *ret_q = q;
+ return 0;
+
+err:
+ for (j = 0; j < i; j++)
+ put_obj(q->entries[j].obj);
+ kfree(q);
+ return -EINVAL;
+}
+
+static void try_wake_any_obj(struct ntsync_obj *obj)
+{
+ switch (obj->type) {
+ case NTSYNC_TYPE_SEM:
+ try_wake_any_sem(obj);
+ break;
+ }
+}
+
+static int ntsync_wait_any(struct ntsync_device *dev, void __user *argp)
+{
+ struct ntsync_wait_args args;
+ struct ntsync_q *q;
+ int signaled;
+ __u32 i;
+ int ret;
+
+ if (copy_from_user(&args, argp, sizeof(args)))
+ return -EFAULT;
+
+ ret = setup_wait(dev, &args, &q);
+ if (ret < 0)
+ return ret;
+
+ /* queue ourselves */
+
+ for (i = 0; i < args.count; i++) {
+ struct ntsync_q_entry *entry = &q->entries[i];
+ struct ntsync_obj *obj = entry->obj;
+
+ spin_lock(&obj->lock);
+ list_add_tail(&entry->node, &obj->any_waiters);
+ spin_unlock(&obj->lock);
+ }
+
+ /* check if we are already signaled */
+
+ for (i = 0; i < args.count; i++) {
+ struct ntsync_obj *obj = q->entries[i].obj;
+
+ if (atomic_read(&q->signaled) != -1)
+ break;
+
+ spin_lock(&obj->lock);
+ try_wake_any_obj(obj);
+ spin_unlock(&obj->lock);
+ }
+
+ /* sleep */
+
+ ret = ntsync_schedule(q, &args);
+
+ /* and finally, unqueue */
+
+ for (i = 0; i < args.count; i++) {
+ struct ntsync_q_entry *entry = &q->entries[i];
+ struct ntsync_obj *obj = entry->obj;
+
+ spin_lock(&obj->lock);
+ list_del(&entry->node);
+ spin_unlock(&obj->lock);
+
+ put_obj(obj);
+ }
+
+ signaled = atomic_read(&q->signaled);
+ if (signaled != -1) {
+ struct ntsync_wait_args __user *user_args = argp;
+
+ /* even if we caught a signal, we need to communicate success */
+ ret = 0;
+
+ if (put_user(signaled, &user_args->index))
+ ret = -EFAULT;
+ } else if (!ret) {
+ ret = -ETIMEDOUT;
+ }
+
+ kfree(q);
+ return ret;
+}
+
static int ntsync_char_open(struct inode *inode, struct file *file)
{
struct ntsync_device *dev;
switch (cmd) {
case NTSYNC_IOC_CREATE_SEM:
return ntsync_create_sem(dev, argp);
+ case NTSYNC_IOC_WAIT_ANY:
+ return ntsync_wait_any(dev, argp);
default:
return -ENOIOCTLCMD;
}
projects / thirdparty / kernel / linux.git / commitdiff
