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Subject[PATCH 4/4] mm: Do periodic rescheduling when freeing objects in kmem_free_up_q()
Date
If the freeing queue has many objects, freeing all of them consecutively
may cause soft lockup especially on a debug kernel. So kmem_free_up_q()
is modified to call cond_resched() if running in the process context.

Signed-off-by: Waiman Long <longman@redhat.com>
---
mm/slab_common.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index dba20b4208f1..633a1d0f6d20 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1622,11 +1622,14 @@ EXPORT_SYMBOL_GPL(kmem_free_q_add);
* kmem_free_up_q - free all the objects in the freeing queue
* @head: freeing queue head
*
- * Free all the objects in the freeing queue.
+ * Free all the objects in the freeing queue. The caller cannot hold any
+ * non-sleeping locks.
*/
void kmem_free_up_q(struct kmem_free_q_head *head)
{
struct kmem_free_q_node *node, *next;
+ bool do_resched = !in_irq();
+ int cnt = 0;

for (node = head->first; node; node = next) {
next = node->next;
@@ -1634,6 +1637,12 @@ void kmem_free_up_q(struct kmem_free_q_head *head)
kmem_cache_free(node->cachep, node);
else
kfree(node);
+ /*
+ * Call cond_resched() every 256 objects freed when in
+ * process context.
+ */
+ if (do_resched && !(++cnt & 0xff))
+ cond_resched();
}
}
EXPORT_SYMBOL_GPL(kmem_free_up_q);
--
2.18.1
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