percpu: acquire pcpu_lock when updating pcpu_nr_empty_pop_pages

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@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # v3.18+

diff --git a/mm/percpu.c b/mm/percpu.c
index 5696039b5c0707eddcb652bc120a8556ca3cc58b..60a6488e9e6d49d5e9c5d4b611a5f5b037342316 100644 (file)
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1011,8 +1011,11 @@ 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();