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Subject[RFC v2 20/34] mm, slub: make locking in deactivate_slab() irq-safe
Date
dectivate_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.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/slub.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 8b0b975bfa36..bba18146def6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2163,6 +2163,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
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;

@@ -2238,7 +2239,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
* 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;
@@ -2249,7 +2250,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
* slabs from diagnostic functions will not see
* any frozen slabs.
*/
- spin_lock(&n->list_lock);
+ spin_lock_irqsave(&n->list_lock, flags);
}
}

@@ -2266,14 +2267,14 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
}

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);
--
2.31.1
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