1 files changed, 17 insertions, 2 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index bb6922a931b1..76f34c0ef29c 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -838,6 +838,7 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
          * back to us). This allows us to do a simple loop to
          * assign the commit to the tail.
          */
+ again:
         while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
                 cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
@@ -853,6 +854,17 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
                         cpu_buffer->commit_page->write;
                 barrier();
         }
+
+        /* again, keep gcc from optimizing */
+        barrier();
+
+        /*
+         * If an interrupt came in just after the first while loop
+         * and pushed the tail page forward, we will be left with
+         * a dangling commit that will never go forward.
+         */
+        if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
+                goto again;
 }
 
 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
@@ -950,12 +962,15 @@ static struct ring_buffer_event *
 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                   unsigned type, unsigned long length, u64 *ts)
 {
-        struct buffer_page *tail_page, *head_page, *reader_page;
+        struct buffer_page *tail_page, *head_page, *reader_page, *commit_page;
         unsigned long tail, write;
         struct ring_buffer *buffer = cpu_buffer->buffer;
         struct ring_buffer_event *event;
         unsigned long flags;
 
+        commit_page = cpu_buffer->commit_page;
+        /* we just need to protect against interrupts */
+        barrier();
         tail_page = cpu_buffer->tail_page;
         write = local_add_return(length, &tail_page->write);
         tail = write - length;
@@ -981,7 +996,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                  * it all the way around the buffer, bail, and warn
                  * about it.
                  */
-                if (unlikely(next_page == cpu_buffer->commit_page)) {
+                if (unlikely(next_page == commit_page)) {
                         WARN_ON_ONCE(1);
                         goto out_unlock;
                 }