The patch titled
Subject: mm/vmalloc: Fix unlock order in s_stop()
has been added to the -mm tree. Its filename is
mm-vmalloc-fix-unlock-order-in-s_stop.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-vmalloc-fix-unlock-order-in-s_stop.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmalloc-fix-unlock-order-in-s_stop.patch
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------------------------------------------------------
From: Waiman Long <longman@xxxxxxxxxx>
Subject: mm/vmalloc: Fix unlock order in s_stop()
When multiple locks are acquired, they should be released in reverse
order. For s_start() and s_stop() in mm/vmalloc.c, that is not the
case.
s_start: mutex_lock(&vmap_purge_lock); spin_lock(&vmap_area_lock);
s_stop : mutex_unlock(&vmap_purge_lock); spin_unlock(&vmap_area_lock);
This unlock sequence, though allowed, is not optimal. If a waiter is
present, mutex_unlock() will need to go through the slowpath of waking
up the waiter with preemption disabled. Fix that by releasing the
spinlock first before the mutex.
Link: https://lkml.kernel.org/r/20201213180843.16938-1-longman@xxxxxxxxxx
Fixes: e36176be1c39 ("mm/vmalloc: rework vmap_area_lock")
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmalloc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/vmalloc.c~mm-vmalloc-fix-unlock-order-in-s_stop
+++ a/mm/vmalloc.c
@@ -3465,11 +3465,11 @@ static void *s_next(struct seq_file *m,
}
static void s_stop(struct seq_file *m, void *p)
- __releases(&vmap_purge_lock)
__releases(&vmap_area_lock)
+ __releases(&vmap_purge_lock)
{
- mutex_unlock(&vmap_purge_lock);
spin_unlock(&vmap_area_lock);
+ mutex_unlock(&vmap_purge_lock);
}
static void show_numa_info(struct seq_file *m, struct vm_struct *v)
_
Patches currently in -mm which might be from longman@xxxxxxxxxx are
mm-vmalloc-fix-unlock-order-in-s_stop.patch
