4.9-stable review patch. If anyone has any objections, please let me know.
------------------
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();