Merge tag 'trace-v4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

gregkh · gregkh · commit f21f7fa263ac · 2018-09-19T07:41:46.000+02:00
Steven writes:
  "Vaibhav Nagarnaik found that modifying the ring buffer size could cause
   a huge latency in the system because it does a while loop to free pages
   without releasing the CPU (on non preempt kernels). In a case where there
   are hundreds of thousands of pages to free it could actually cause a system
   stall. A properly place cond_resched() solves this issue."
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
@@ -1546,6 +1546,8 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
 	tmp_iter_page = first_page;
 
 	do {
+		cond_resched();
+
 		to_remove_page = tmp_iter_page;
 		rb_inc_page(cpu_buffer, &tmp_iter_page);
 
