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authorWaiman Long <longman@redhat.com>2020-12-14 19:08:59 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-15 12:13:42 -0800
commit0a7dd4e901b8a4ee040ba953900d1d7120b34ee5 (patch)
tree3cb09b528dc96d2442cabd6a62b4415696eb1287
parente924d461f2c3ca3f31f48b0be421487d99fa2e5e (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.c4
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)