1 files changed, 13 insertions, 14 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 52dea5dd5362..a1651edc48d5 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -692,10 +692,7 @@ static void rb_time_set(rb_time_t *t, u64 val)
 static inline bool
 rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set)
 {
-	unsigned long ret;
-
-	ret = local_cmpxchg(l, expect, set);
-	return ret == expect;
+	return local_try_cmpxchg(l, &expect, set);
 }
 
 static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
@@ -752,9 +749,7 @@ static void rb_time_set(rb_time_t *t, u64 val)
 
 static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
 {
-	u64 val;
-	val = local64_cmpxchg(&t->time, expect, set);
-	return val == expect;
+	return local64_try_cmpxchg(&t->time, &expect, set);
 }
 #endif
 
@@ -1494,14 +1489,11 @@ static bool rb_head_page_replace(struct buffer_page *old,
 {
 	unsigned long *ptr = (unsigned long *)&old->list.prev->next;
 	unsigned long val;
-	unsigned long ret;
 
 	val = *ptr & ~RB_FLAG_MASK;
 	val |= RB_PAGE_HEAD;
 
-	ret = cmpxchg(ptr, val, (unsigned long)&new->list);
-
-	return ret == val;
+	return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
 }
 
 /*
@@ -2206,6 +2198,8 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
 				err = -ENOMEM;
 				goto out_err;
 			}
+
+			cond_resched();
 		}
 
 		cpus_read_lock();
@@ -2396,6 +2390,11 @@ rb_iter_head_event(struct ring_buffer_iter *iter)
 	 */
 	commit = rb_page_commit(iter_head_page);
 	smp_rmb();
+
+	/* An event needs to be at least 8 bytes in size */
+	if (iter->head > commit - 8)
+		goto reset;
+
 	event = __rb_page_index(iter_head_page, iter->head);
 	length = rb_event_length(event);
 
@@ -3003,7 +3002,6 @@ rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
 {
 	unsigned long new_index, old_index;
 	struct buffer_page *bpage;
-	unsigned long index;
 	unsigned long addr;
 	u64 write_stamp;
 	u64 delta;
@@ -3060,8 +3058,9 @@ rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
 		 */
 		old_index += write_mask;
 		new_index += write_mask;
-		index = local_cmpxchg(&bpage->write, old_index, new_index);
-		if (index == old_index) {
+
+		/* caution: old_index gets updated on cmpxchg failure */
+		if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
 			/* update counters */
 			local_sub(event_length, &cpu_buffer->entries_bytes);
 			return true;