ring-buffer: Check if buffer exists before polling

[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 e444ff88f0a425a00a4921291b46678b6a7efe21..8e94c1102636670dabf637e5aff3e2e65fa661bc 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -543,7 +543,7 @@ static void rb_wake_up_waiters(struct irq_work *work)
  * 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.
  */
-void ring_buffer_wait(struct ring_buffer *buffer, int cpu)
+int ring_buffer_wait(struct ring_buffer *buffer, int cpu)
 {
        struct ring_buffer_per_cpu *cpu_buffer;
        DEFINE_WAIT(wait);
@@ -557,6 +557,8 @@ void ring_buffer_wait(struct ring_buffer *buffer, int cpu)
        if (cpu == RING_BUFFER_ALL_CPUS)
                work = &buffer->irq_work;
        else {
+               if (!cpumask_test_cpu(cpu, buffer->cpumask))
+                       return -ENODEV;
                cpu_buffer = buffer->buffers[cpu];
                work = &cpu_buffer->irq_work;
        }
@@ -591,6 +593,7 @@ void ring_buffer_wait(struct ring_buffer *buffer, int cpu)
                schedule();
 
        finish_wait(&work->waiters, &wait);
+       return 0;
 }
 
 /**
@@ -2396,6 +2399,13 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
        write &= RB_WRITE_MASK;
        tail = write - length;
 
+       /*
+        * If this is the first commit on the page, then it has the same
+        * timestamp as the page itself.
+        */
+       if (!tail)
+               delta = 0;
+
        /* See if we shot pass the end of this buffer page */
        if (unlikely(write > BUF_PAGE_SIZE))
                return rb_move_tail(cpu_buffer, length, tail,