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-rw-r--r--kernel/trace/ring_buffer.c19
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)
838 * back to us). This allows us to do a simple loop to 838 * back to us). This allows us to do a simple loop to
839 * assign the commit to the tail. 839 * assign the commit to the tail.
840 */ 840 */
841 again:
841 while (cpu_buffer->commit_page != cpu_buffer->tail_page) { 842 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
842 cpu_buffer->commit_page->page->commit = 843 cpu_buffer->commit_page->page->commit =
843 cpu_buffer->commit_page->write; 844 cpu_buffer->commit_page->write;
@@ -853,6 +854,17 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
853 cpu_buffer->commit_page->write; 854 cpu_buffer->commit_page->write;
854 barrier(); 855 barrier();
855 } 856 }
857
858 /* again, keep gcc from optimizing */
859 barrier();
860
861 /*
862 * If an interrupt came in just after the first while loop
863 * and pushed the tail page forward, we will be left with
864 * a dangling commit that will never go forward.
865 */
866 if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
867 goto again;
856} 868}
857 869
858static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer) 870static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
@@ -950,12 +962,15 @@ static struct ring_buffer_event *
950__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, 962__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
951 unsigned type, unsigned long length, u64 *ts) 963 unsigned type, unsigned long length, u64 *ts)
952{ 964{
953 struct buffer_page *tail_page, *head_page, *reader_page; 965 struct buffer_page *tail_page, *head_page, *reader_page, *commit_page;
954 unsigned long tail, write; 966 unsigned long tail, write;
955 struct ring_buffer *buffer = cpu_buffer->buffer; 967 struct ring_buffer *buffer = cpu_buffer->buffer;
956 struct ring_buffer_event *event; 968 struct ring_buffer_event *event;
957 unsigned long flags; 969 unsigned long flags;
958 970
971 commit_page = cpu_buffer->commit_page;
972 /* we just need to protect against interrupts */
973 barrier();
959 tail_page = cpu_buffer->tail_page; 974 tail_page = cpu_buffer->tail_page;
960 write = local_add_return(length, &tail_page->write); 975 write = local_add_return(length, &tail_page->write);
961 tail = write - length; 976 tail = write - length;
@@ -981,7 +996,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
981 * it all the way around the buffer, bail, and warn 996 * it all the way around the buffer, bail, and warn
982 * about it. 997 * about it.
983 */ 998 */
984 if (unlikely(next_page == cpu_buffer->commit_page)) { 999 if (unlikely(next_page == commit_page)) {
985 WARN_ON_ONCE(1); 1000 WARN_ON_ONCE(1);
986 goto out_unlock; 1001 goto out_unlock;
987 } 1002 }