From: Vaibhav Nagarnaik Date: Fri, 7 Sep 2018 22:31:29 +0000 (-0700) Subject: ring-buffer: Allow for rescheduling when removing pages X-Git-Tag: Ubuntu-5.2.0-15.16~3557^2 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=83f365554e47997ec68dc4eca3f5dce525cd15c3;p=mirror_ubuntu-eoan-kernel.git ring-buffer: Allow for rescheduling when removing pages 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 Cc: stable@vger.kernel.org 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) --- diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 1d92d4a982fd..65bd4616220d 100644 --- 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);