diff options
| author | Waiman Long <longman@redhat.com> | 2020-12-14 19:08:59 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-15 12:13:42 -0800 |
| commit | 0a7dd4e901b8a4ee040ba953900d1d7120b34ee5 (patch) | |
| tree | 3cb09b528dc96d2442cabd6a62b4415696eb1287 | |
| parent | e924d461f2c3ca3f31f48b0be421487d99fa2e5e (diff) | |
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@redhat.com
Fixes: e36176be1c39 ("mm/vmalloc: rework vmap_area_lock")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/vmalloc.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 5d310f510ee5..c4678ab25078 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3465,11 +3465,11 @@ static void *s_next(struct seq_file *m, void *p, loff_t *pos) } 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) |