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authorPeter Zijlstra <peterz@infradead.org>2021-09-23 14:11:04 -0300
committerPeter Zijlstra <peterz@infradead.org>2021-10-07 13:51:11 +0200
commitbff7c57c2f50dca7b5e320f499e0898c3fb8a9ff (patch)
tree0e7e8366851e1f33ad0d929fb5e78e1ae026ff93 /kernel/futex
parenta046f1a0d3e320cfee6bdac336416a537f49e7c6 (diff)
downloadlinux-bff7c57c2f50dca7b5e320f499e0898c3fb8a9ff.tar.bz2
futex: Simplify double_lock_hb()
We need to make sure that all requeue operations take the hash bucket locks in the same order to avoid deadlock. Simplify the current double_lock_hb implementation by making sure hb1 is always the "smallest" bucket to avoid extra checks. [André: Add commit description] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: André Almeida <andrealmeid@collabora.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: André Almeida <andrealmeid@collabora.com> Link: https://lore.kernel.org/r/20210923171111.300673-16-andrealmeid@collabora.com
Diffstat (limited to 'kernel/futex')
-rw-r--r--kernel/futex/futex.h14
1 files changed, 6 insertions, 8 deletions
diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index fe847f57dad5..465f7bd5caef 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -239,14 +239,12 @@ extern int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked);
static inline void
double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
{
- if (hb1 <= hb2) {
- spin_lock(&hb1->lock);
- if (hb1 < hb2)
- spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
- } else { /* hb1 > hb2 */
- spin_lock(&hb2->lock);
- spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
- }
+ if (hb1 > hb2)
+ swap(hb1, hb2);
+
+ spin_lock(&hb1->lock);
+ if (hb1 != hb2)
+ spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
}
static inline void