4 files changed, 76 insertions, 21 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index ccec55394380..cfbfa15a46ba 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -397,7 +397,7 @@ prototypes:
 };
 
 locking rules:
-        All except ->poll() may block.
+        All may block.
                         BKL
 llseek:                 no      (see below)
 read:                   no
diff --git a/drivers/media/video/v4l1-compat.c b/drivers/media/video/v4l1-compat.c
index d450cab20be4..b617bf05e2d7 100644
--- a/drivers/media/video/v4l1-compat.c
+++ b/drivers/media/video/v4l1-compat.c
@@ -203,7 +203,6 @@ static int poll_one(struct file *file, struct poll_wqueues *pwq)
         table = &pwq->pt;
         for (;;) {
                 int mask;
-                set_current_state(TASK_INTERRUPTIBLE);
                 mask = file->f_op->poll(file, table);
                 if (mask & POLLIN)
                         break;
@@ -212,9 +211,8 @@ static int poll_one(struct file *file, struct poll_wqueues *pwq)
                         retval = -ERESTARTSYS;
                         break;
                 }
-                schedule();
+                poll_schedule(pwq, TASK_INTERRUPTIBLE);
         }
-        set_current_state(TASK_RUNNING);
         poll_freewait(pwq);
         return retval;
 }
diff --git a/fs/select.c b/fs/select.c
index 87df51eadcf2..08b91beed806 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -109,11 +109,11 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 void poll_initwait(struct poll_wqueues *pwq)
 {
         init_poll_funcptr(&pwq->pt, __pollwait);
+        pwq->polling_task = current;
         pwq->error = 0;
         pwq->table = NULL;
         pwq->inline_index = 0;
 }
-
 EXPORT_SYMBOL(poll_initwait);
 
 static void free_poll_entry(struct poll_table_entry *entry)
@@ -142,12 +142,10 @@ void poll_freewait(struct poll_wqueues *pwq)
                 free_page((unsigned long) old);
         }
 }
-
 EXPORT_SYMBOL(poll_freewait);
 
-static struct poll_table_entry *poll_get_entry(poll_table *_p)
+static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
 {
-        struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
         struct poll_table_page *table = p->table;
 
         if (p->inline_index < N_INLINE_POLL_ENTRIES)
@@ -159,7 +157,6 @@ static struct poll_table_entry *poll_get_entry(poll_table *_p)
                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
                 if (!new_table) {
                         p->error = -ENOMEM;
-                        __set_current_state(TASK_RUNNING);
                         return NULL;
                 }
                 new_table->entry = new_table->entries;
@@ -171,20 +168,75 @@ static struct poll_table_entry *poll_get_entry(poll_table *_p)
         return table->entry++;
 }
 
+static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
+{
+        struct poll_wqueues *pwq = wait->private;
+        DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
+
+        /*
+         * Although this function is called under waitqueue lock, LOCK
+         * doesn't imply write barrier and the users expect write
+         * barrier semantics on wakeup functions.  The following
+         * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
+         * and is paired with set_mb() in poll_schedule_timeout.
+         */
+        smp_wmb();
+        pwq->triggered = 1;
+
+        /*
+         * Perform the default wake up operation using a dummy
+         * waitqueue.
+         *
+         * TODO: This is hacky but there currently is no interface to
+         * pass in @sync.  @sync is scheduled to be removed and once
+         * that happens, wake_up_process() can be used directly.
+         */
+        return default_wake_function(&dummy_wait, mode, sync, key);
+}
+
 /* Add a new entry */
 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
                                 poll_table *p)
 {
-        struct poll_table_entry *entry = poll_get_entry(p);
+        struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
+        struct poll_table_entry *entry = poll_get_entry(pwq);
         if (!entry)
                 return;
         get_file(filp);
         entry->filp = filp;
         entry->wait_address = wait_address;
-        init_waitqueue_entry(&entry->wait, current);
+        init_waitqueue_func_entry(&entry->wait, pollwake);
+        entry->wait.private = pwq;
         add_wait_queue(wait_address, &entry->wait);
 }
 
+int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
+                          ktime_t *expires, unsigned long slack)
+{
+        int rc = -EINTR;
+
+        set_current_state(state);
+        if (!pwq->triggered)
+                rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
+        __set_current_state(TASK_RUNNING);
+
+        /*
+         * Prepare for the next iteration.
+         *
+         * The following set_mb() serves two purposes.  First, it's
+         * the counterpart rmb of the wmb in pollwake() such that data
+         * written before wake up is always visible after wake up.
+         * Second, the full barrier guarantees that triggered clearing
+         * doesn't pass event check of the next iteration.  Note that
+         * this problem doesn't exist for the first iteration as
+         * add_wait_queue() has full barrier semantics.
+         */
+        set_mb(pwq->triggered, 0);
+
+        return rc;
+}
+EXPORT_SYMBOL(poll_schedule_timeout);
+
 /**
  * poll_select_set_timeout - helper function to setup the timeout value
  * @to:         pointer to timespec variable for the final timeout
@@ -340,8 +392,6 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
         for (;;) {
                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 
-                set_current_state(TASK_INTERRUPTIBLE);
-
                 inp = fds->in; outp = fds->out; exp = fds->ex;
                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 
@@ -411,10 +461,10 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
                         to = &expire;
                 }
 
-                if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
+                if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
+                                           to, slack))
                         timed_out = 1;
         }
-        __set_current_state(TASK_RUNNING);
 
         poll_freewait(&table);
 
@@ -666,7 +716,6 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
         for (;;) {
                 struct poll_list *walk;
 
-                set_current_state(TASK_INTERRUPTIBLE);
                 for (walk = list; walk != NULL; walk = walk->next) {
                         struct pollfd * pfd, * pfd_end;
 
@@ -709,10 +758,9 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
                         to = &expire;
                 }
 
-                if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
+                if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
                         timed_out = 1;
         }
-        __set_current_state(TASK_RUNNING);
         return count;
 }
 
diff --git a/include/linux/poll.h b/include/linux/poll.h
index badd98ab06f6..8c24ef8d9976 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -46,9 +46,9 @@ static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
 }
 
 struct poll_table_entry {
-        struct file * filp;
+        struct file *filp;
         wait_queue_t wait;
-        wait_queue_head_t * wait_address;
+        wait_queue_head_t *wait_address;
 };
 
 /*
@@ -56,7 +56,9 @@ struct poll_table_entry {
  */
 struct poll_wqueues {
         poll_table pt;
-        struct poll_table_page * table;
+        struct poll_table_page *table;
+        struct task_struct *polling_task;
+        int triggered;
         int error;
         int inline_index;
         struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
@@ -64,6 +66,13 @@ struct poll_wqueues {
 
 extern void poll_initwait(struct poll_wqueues *pwq);
 extern void poll_freewait(struct poll_wqueues *pwq);
+extern int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
+                                 ktime_t *expires, unsigned long slack);
+
+static inline int poll_schedule(struct poll_wqueues *pwq, int state)
+{
+        return poll_schedule_timeout(pwq, state, NULL, 0);
+}
 
 /*
  * Scaleable version of the fd_set.