From ae000eff9069efc2cc848b3e794d01496f81fdb2 Mon Sep 17 00:00:00 2001 From: Vaibhav Nagarnaik Date: Fri, 7 Sep 2018 15:31:29 -0700 Subject: [PATCH] ring-buffer: Allow for rescheduling when removing pages commit 83f365554e47997ec68dc4eca3f5dce525cd15c3 upstream. When reducing ring buffer size, pages are removed by scheduling a work item on each CPU for the corresponding CPU ring buffer. After the pages are removed from ring buffer linked list, the pages are free()d in a tight loop. The loop does not give up CPU until all pages are removed. In a worst case behavior, when lot of pages are to be freed, it can cause system stall. After the pages are removed from the list, the free() can happen while the work is rescheduled. Call cond_resched() in the loop to prevent the system hangup. Link: http://lkml.kernel.org/r/20180907223129.71994-1-vnagarnaik@google.com Fixes: 83f40318dab00 ("ring-buffer: Make removal of ring buffer pages atomic") Reported-by: Jason Behmer Signed-off-by: Vaibhav Nagarnaik Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Ben Hutchings --- kernel/trace/ring_buffer.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index ee01bb53e420..107e8ce1a87e 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1541,6 +1541,8 @@ 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);