This is a note to let you know that I've just added the patch titled percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: percpu-acquire-pcpu_lock-when-updating-pcpu_nr_empty_pop_pages.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 320661b08dd6f1746d5c7ab4eb435ec64b97cd45 Mon Sep 17 00:00:00 2001 From: Tahsin Erdogan <tahsin@xxxxxxxxxx> Date: Sat, 25 Feb 2017 13:00:19 -0800 Subject: percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages From: Tahsin Erdogan <tahsin@xxxxxxxxxx> commit 320661b08dd6f1746d5c7ab4eb435ec64b97cd45 upstream. Update to pcpu_nr_empty_pop_pages in pcpu_alloc() is currently done without holding pcpu_lock. This can lead to bad updates to the variable. Add missing lock calls. Fixes: b539b87fed37 ("percpu: implmeent pcpu_nr_empty_pop_pages and chunk->nr_populated") Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/percpu.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1010,8 +1010,11 @@ area_found: mutex_unlock(&pcpu_alloc_mutex); } - if (chunk != pcpu_reserved_chunk) + if (chunk != pcpu_reserved_chunk) { + spin_lock_irqsave(&pcpu_lock, flags); pcpu_nr_empty_pop_pages -= occ_pages; + spin_unlock_irqrestore(&pcpu_lock, flags); + } if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW) pcpu_schedule_balance_work(); Patches currently in stable-queue which might be from tahsin@xxxxxxxxxx are queue-4.9/percpu-acquire-pcpu_lock-when-updating-pcpu_nr_empty_pop_pages.patch