From: Sebastian Andrzej Siewior Date: Thu, 26 Jul 2018 18:52:00 +0200 Subject: [PATCH 224/342] crypto: cryptd - add a lock instead preempt_disable/local_bh_disable Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=a65b405a299e90f7a3a0de278af917a86e2c1f07 cryptd has a per-CPU lock which protected with local_bh_disable() and preempt_disable(). Add an explicit spin_lock to make the locking context more obvious and visible to lockdep. Since it is a per-CPU lock, there should be no lock contention on the actual spinlock. There is a small race-window where we could be migrated to another CPU after the cpu_queue has been obtain. This is not a problem because the actual ressource is protected by the spinlock. Signed-off-by: Sebastian Andrzej Siewior --- crypto/cryptd.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/crypto/cryptd.c b/crypto/cryptd.c index e0c8e907b086..e079f9a70201 100644 --- a/crypto/cryptd.c +++ b/crypto/cryptd.c @@ -39,6 +39,7 @@ MODULE_PARM_DESC(cryptd_max_cpu_qlen, "Set cryptd Max queue depth"); struct cryptd_cpu_queue { struct crypto_queue queue; struct work_struct work; + spinlock_t qlock; }; struct cryptd_queue { @@ -117,6 +118,7 @@ static int cryptd_init_queue(struct cryptd_queue *queue, cpu_queue = per_cpu_ptr(queue->cpu_queue, cpu); crypto_init_queue(&cpu_queue->queue, max_cpu_qlen); INIT_WORK(&cpu_queue->work, cryptd_queue_worker); + spin_lock_init(&cpu_queue->qlock); } pr_info("cryptd: max_cpu_qlen set to %d\n", max_cpu_qlen); return 0; @@ -141,8 +143,10 @@ static int cryptd_enqueue_request(struct cryptd_queue *queue, struct cryptd_cpu_queue *cpu_queue; atomic_t *refcnt; - cpu = get_cpu(); - cpu_queue = this_cpu_ptr(queue->cpu_queue); + cpu_queue = raw_cpu_ptr(queue->cpu_queue); + spin_lock_bh(&cpu_queue->qlock); + cpu = smp_processor_id(); + err = crypto_enqueue_request(&cpu_queue->queue, request); refcnt = crypto_tfm_ctx(request->tfm); @@ -158,7 +162,7 @@ static int cryptd_enqueue_request(struct cryptd_queue *queue, atomic_inc(refcnt); out_put_cpu: - put_cpu(); + spin_unlock_bh(&cpu_queue->qlock); return err; } @@ -174,16 +178,11 @@ static void cryptd_queue_worker(struct work_struct *work) cpu_queue = container_of(work, struct cryptd_cpu_queue, work); /* * Only handle one request at a time to avoid hogging crypto workqueue. - * preempt_disable/enable is used to prevent being preempted by - * cryptd_enqueue_request(). local_bh_disable/enable is used to prevent - * cryptd_enqueue_request() being accessed from software interrupts. */ - local_bh_disable(); - preempt_disable(); + spin_lock_bh(&cpu_queue->qlock); backlog = crypto_get_backlog(&cpu_queue->queue); req = crypto_dequeue_request(&cpu_queue->queue); - preempt_enable(); - local_bh_enable(); + spin_unlock_bh(&cpu_queue->qlock); if (!req) return;