1 files changed, 54 insertions, 27 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2d75c94ae87d..a56e07c8d15b 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -538,16 +538,18 @@ static void rb_wake_up_waiters(struct irq_work *work)
  * ring_buffer_wait - wait for input to the ring buffer
  * @buffer: buffer to wait on
  * @cpu: the cpu buffer to wait on
+ * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
  *
  * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
  * as data is added to any of the @buffer's cpu buffers. Otherwise
  * it will wait for data to be added to a specific cpu buffer.
  */
-int ring_buffer_wait(struct ring_buffer *buffer, int cpu)
+int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
 {
-        struct ring_buffer_per_cpu *cpu_buffer;
+        struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
         DEFINE_WAIT(wait);
         struct rb_irq_work *work;
+        int ret = 0;
 
         /*
          * Depending on what the caller is waiting for, either any
@@ -564,36 +566,61 @@ int ring_buffer_wait(struct ring_buffer *buffer, int cpu)
         }
 
 
-        prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
+        while (true) {
+                prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
 
-        /*
-         * The events can happen in critical sections where
-         * checking a work queue can cause deadlocks.
-         * After adding a task to the queue, this flag is set
-         * only to notify events to try to wake up the queue
-         * using irq_work.
-         *
-         * We don't clear it even if the buffer is no longer
-         * empty. The flag only causes the next event to run
-         * irq_work to do the work queue wake up. The worse
-         * that can happen if we race with !trace_empty() is that
-         * an event will cause an irq_work to try to wake up
-         * an empty queue.
-         *
-         * There's no reason to protect this flag either, as
-         * the work queue and irq_work logic will do the necessary
-         * synchronization for the wake ups. The only thing
-         * that is necessary is that the wake up happens after
-         * a task has been queued. It's OK for spurious wake ups.
-         */
-        work->waiters_pending = true;
+                /*
+                 * The events can happen in critical sections where
+                 * checking a work queue can cause deadlocks.
+                 * After adding a task to the queue, this flag is set
+                 * only to notify events to try to wake up the queue
+                 * using irq_work.
+                 *
+                 * We don't clear it even if the buffer is no longer
+                 * empty. The flag only causes the next event to run
+                 * irq_work to do the work queue wake up. The worse
+                 * that can happen if we race with !trace_empty() is that
+                 * an event will cause an irq_work to try to wake up
+                 * an empty queue.
+                 *
+                 * There's no reason to protect this flag either, as
+                 * the work queue and irq_work logic will do the necessary
+                 * synchronization for the wake ups. The only thing
+                 * that is necessary is that the wake up happens after
+                 * a task has been queued. It's OK for spurious wake ups.
+                 */
+                work->waiters_pending = true;
+
+                if (signal_pending(current)) {
+                        ret = -EINTR;
+                        break;
+                }
+
+                if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
+                        break;
+
+                if (cpu != RING_BUFFER_ALL_CPUS &&
+                    !ring_buffer_empty_cpu(buffer, cpu)) {
+                        unsigned long flags;
+                        bool pagebusy;
+
+                        if (!full)
+                                break;
+
+                        raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+                        pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
+                        raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+                        if (!pagebusy)
+                                break;
+                }
 
-        if ((cpu == RING_BUFFER_ALL_CPUS && ring_buffer_empty(buffer)) ||
-            (cpu != RING_BUFFER_ALL_CPUS && ring_buffer_empty_cpu(buffer, cpu)))
                 schedule();
+        }
 
         finish_wait(&work->waiters, &wait);
-        return 0;
+
+        return ret;
 }
 
 /**