[019/147] mm, slub: make locking in deactivate_slab() irq-safe

Commit Message

Andrew Morton Sept. 8, 2021, 2:53 a.m. UTC

From: Vlastimil Babka <[e-mail]>
Subject: mm, slub: make locking in deactivate_slab() irq-safe

deactivate_slab() now no longer touches the kmem_cache_cpu structure, so
it will be possible to call it with irqs enabled.  Just convert the
spin_lock calls to their irq saving/restoring variants to make it
irq-safe.

Note we now have to use cmpxchg_double_slab() for irq-safe slab_lock(),
because in some situations we don't take the list_lock, which would
disable irqs.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Jesper Dangaard Brouer <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Cc: Qian Cai <[e-mail]>
Cc: Sebastian Andrzej Siewior <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/slub.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Patch

--- a/mm/slub.c~mm-slub-make-locking-in-deactivate_slab-irq-safe
+++ a/mm/slub.c
@@ -2223,6 +2223,7 @@  static void deactivate_slab(struct kmem_
 	enum slab_modes l = M_NONE, m = M_NONE;
 	void *nextfree, *freelist_iter, *freelist_tail;
 	int tail = DEACTIVATE_TO_HEAD;
+	unsigned long flags = 0;
 	struct page new;
 	struct page old;
 
@@ -2298,7 +2299,7 @@  redo:
 			 * that acquire_slab() will see a slab page that
 			 * is frozen
 			 */
-			spin_lock(&n->list_lock);
+			spin_lock_irqsave(&n->list_lock, flags);
 		}
 	} else {
 		m = M_FULL;
@@ -2309,7 +2310,7 @@  redo:
 			 * slabs from diagnostic functions will not see
 			 * any frozen slabs.
 			 */
-			spin_lock(&n->list_lock);
+			spin_lock_irqsave(&n->list_lock, flags);
 		}
 	}
 
@@ -2326,14 +2327,14 @@  redo:
 	}
 
 	l = m;
-	if (!__cmpxchg_double_slab(s, page,
+	if (!cmpxchg_double_slab(s, page,
 				old.freelist, old.counters,
 				new.freelist, new.counters,
 				"unfreezing slab"))
 		goto redo;
 
 	if (lock)
-		spin_unlock(&n->list_lock);
+		spin_unlock_irqrestore(&n->list_lock, flags);
 
 	if (m == M_PARTIAL)
 		stat(s, tail);