1 files changed, 27 insertions, 9 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ebd996f8710e..a626211ceb9a 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -555,7 +555,7 @@ static bool update_marker_trace(struct trace_array *tr, int enabled)
 	lockdep_assert_held(&event_mutex);
 
 	if (enabled) {
-		if (!list_empty(&tr->marker_list))
+		if (tr->trace_flags & TRACE_ITER(COPY_MARKER))
 			return false;
 
 		list_add_rcu(&tr->marker_list, &marker_copies);
@@ -563,10 +563,10 @@ static bool update_marker_trace(struct trace_array *tr, int enabled)
 		return true;
 	}
 
-	if (list_empty(&tr->marker_list))
+	if (!(tr->trace_flags & TRACE_ITER(COPY_MARKER)))
 		return false;
 
-	list_del_init(&tr->marker_list);
+	list_del_rcu(&tr->marker_list);
 	tr->trace_flags &= ~TRACE_ITER(COPY_MARKER);
 	return true;
 }
@@ -6784,6 +6784,23 @@ char *trace_user_fault_read(struct trace_user_buf_info *tinfo,
 
 	do {
 		/*
+		 * It is possible that something is trying to migrate this
+		 * task. What happens then, is when preemption is enabled,
+		 * the migration thread will preempt this task, try to
+		 * migrate it, fail, then let it run again. That will
+		 * cause this to loop again and never succeed.
+		 * On failures, enabled and disable preemption with
+		 * migration enabled, to allow the migration thread to
+		 * migrate this task.
+		 */
+		if (trys) {
+			preempt_enable_notrace();
+			preempt_disable_notrace();
+			cpu = smp_processor_id();
+			buffer = per_cpu_ptr(tinfo->tbuf, cpu)->buf;
+		}
+
+		/*
 		 * If for some reason, copy_from_user() always causes a context
 		 * switch, this would then cause an infinite loop.
 		 * If this task is preempted by another user space task, it
@@ -9744,18 +9761,19 @@ static int __remove_instance(struct trace_array *tr)
 
 	list_del(&tr->list);
 
-	/* Disable all the flags that were enabled coming in */
-	for (i = 0; i < TRACE_FLAGS_MAX_SIZE; i++) {
-		if ((1ULL << i) & ZEROED_TRACE_FLAGS)
-			set_tracer_flag(tr, 1ULL << i, 0);
-	}
-
 	if (printk_trace == tr)
 		update_printk_trace(&global_trace);
 
+	/* Must be done before disabling all the flags */
 	if (update_marker_trace(tr, 0))
 		synchronize_rcu();
 
+	/* Disable all the flags that were enabled coming in */
+	for (i = 0; i < TRACE_FLAGS_MAX_SIZE; i++) {
+		if ((1ULL << i) & ZEROED_TRACE_FLAGS)
+			set_tracer_flag(tr, 1ULL << i, 0);
+	}
+
 	tracing_set_nop(tr);
 	clear_ftrace_function_probes(tr);
 	event_trace_del_tracer(tr);