Merge tag 'trace-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux...

[firefly-linux-kernel-4.4.55.git] / kernel / trace / ring_buffer.c

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index a28bdd17c853ed5cb9ce7fc1a843b82575579148..7a4104cb95cb28792364d60c0abb5826a3a0aad5 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -535,16 +535,18 @@ 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
@@ -561,36 +563,61 @@ 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;
 }
 
 /**