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| author | Peter Zijlstra <peterz@infradead.org> | 2021-09-23 19:11:04 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-10-07 13:51:11 +0200 |
| commit | bff7c57c2f50dca7b5e320f499e0898c3fb8a9ff (patch) | |
| tree | 0e7e8366851e1f33ad0d929fb5e78e1ae026ff93 /kernel/futex/futex.h | |
| parent | futex: Split out wait/wake (diff) | |
| download | linux-bff7c57c2f50dca7b5e320f499e0898c3fb8a9ff.tar.xz linux-bff7c57c2f50dca7b5e320f499e0898c3fb8a9ff.zip | |
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/futex.h')
| -rw-r--r-- | kernel/futex/futex.h | 14 |
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 |