Merge tag 'trace-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux...

[linux-2.6-microblaze.git] / kernel / trace / ring_buffer.c

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 0d748f1..834b361 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3097,6 +3097,10 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
                if (RB_WARN_ON(cpu_buffer,
                               rb_is_reader_page(cpu_buffer->tail_page)))
                        return;
+               /*
+                * No need for a memory barrier here, as the update
+                * of the tail_page did it for this page.
+                */
                local_set(&cpu_buffer->commit_page->page->commit,
                          rb_page_write(cpu_buffer->commit_page));
                rb_inc_page(&cpu_buffer->commit_page);
@@ -3106,6 +3110,8 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
        while (rb_commit_index(cpu_buffer) !=
               rb_page_write(cpu_buffer->commit_page)) {
 
+               /* Make sure the readers see the content of what is committed. */
+               smp_wmb();
                local_set(&cpu_buffer->commit_page->page->commit,
                          rb_page_write(cpu_buffer->commit_page));
                RB_WARN_ON(cpu_buffer,
@@ -4681,7 +4687,12 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
 
        /*
         * Make sure we see any padding after the write update
-        * (see rb_reset_tail())
+        * (see rb_reset_tail()).
+        *
+        * In addition, a writer may be writing on the reader page
+        * if the page has not been fully filled, so the read barrier
+        * is also needed to make sure we see the content of what is
+        * committed by the writer (see rb_set_commit_to_write()).
         */
        smp_rmb();