crypto: mxs-dcp - Fix wait logic on chan threads

When compiling with CONFIG_DEBUG_ATOMIC_SLEEP=y the mxs-dcp driver
prints warnings such as:

WARNING: CPU: 0 PID: 120 at kernel/sched/core.c:7736 __might_sleep+0x98/0x9c
do not call blocking ops when !TASK_RUNNING; state=1 set at [<8081978c>] dcp_chan_thread_sha+0x3c/0x2ec

The problem is that blocking ops will manipulate current->state
themselves so it is not allowed to call them between
set_current_state(TASK_INTERRUPTIBLE) and schedule().

Fix this by converting the per-chan mutex to a spinlock (it only
protects tiny list ops anyway) and rearranging the wait logic so that
callbacks are called current->state as TASK_RUNNING. Those callbacks
will indeed call blocking ops themselves so this is required.

Cc: <stable@vger.kernel.org>
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/mxs-dcp.c

@@ -63,7 +63,7 @@ struct dcp {
 	struct dcp_coherent_block	*coh;
 
 	struct completion		completion[DCP_MAX_CHANS];
-	struct mutex			mutex[DCP_MAX_CHANS];
+	spinlock_t			lock[DCP_MAX_CHANS];
 	struct task_struct		*thread[DCP_MAX_CHANS];
 	struct crypto_queue		queue[DCP_MAX_CHANS];
 };
@@ -349,13 +349,20 @@ static int dcp_chan_thread_aes(void *data)
 
 	int ret;
 
-	do {
-		__set_current_state(TASK_INTERRUPTIBLE);
+	while (!kthread_should_stop()) {
+		set_current_state(TASK_INTERRUPTIBLE);
 
-		mutex_lock(&sdcp->mutex[chan]);
+		spin_lock(&sdcp->lock[chan]);
 		backlog = crypto_get_backlog(&sdcp->queue[chan]);
 		arq = crypto_dequeue_request(&sdcp->queue[chan]);
-		mutex_unlock(&sdcp->mutex[chan]);
+		spin_unlock(&sdcp->lock[chan]);
+
+		if (!backlog && !arq) {
+			schedule();
+			continue;
+		}
+
+		set_current_state(TASK_RUNNING);
 
 		if (backlog)
 			backlog->complete(backlog, -EINPROGRESS);
@@ -363,11 +370,8 @@ static int dcp_chan_thread_aes(void *data)
 		if (arq) {
 			ret = mxs_dcp_aes_block_crypt(arq);
 			arq->complete(arq, ret);
-			continue;
 		}
-
-		schedule();
-	} while (!kthread_should_stop());
+	}
 
 	return 0;
 }
@@ -409,9 +413,9 @@ static int mxs_dcp_aes_enqueue(struct ablkcipher_request *req, int enc, int ecb)
 	rctx->ecb = ecb;
 	actx->chan = DCP_CHAN_CRYPTO;
 
-	mutex_lock(&sdcp->mutex[actx->chan]);
+	spin_lock(&sdcp->lock[actx->chan]);
 	ret = crypto_enqueue_request(&sdcp->queue[actx->chan], &req->base);
-	mutex_unlock(&sdcp->mutex[actx->chan]);
+	spin_unlock(&sdcp->lock[actx->chan]);
 
 	wake_up_process(sdcp->thread[actx->chan]);
 
@@ -640,13 +644,20 @@ static int dcp_chan_thread_sha(void *data)
 	struct ahash_request *req;
 	int ret, fini;
 
-	do {
-		__set_current_state(TASK_INTERRUPTIBLE);
+	while (!kthread_should_stop()) {
+		set_current_state(TASK_INTERRUPTIBLE);
 
-		mutex_lock(&sdcp->mutex[chan]);
+		spin_lock(&sdcp->lock[chan]);
 		backlog = crypto_get_backlog(&sdcp->queue[chan]);
 		arq = crypto_dequeue_request(&sdcp->queue[chan]);
-		mutex_unlock(&sdcp->mutex[chan]);
+		spin_unlock(&sdcp->lock[chan]);
+
+		if (!backlog && !arq) {
+			schedule();
+			continue;
+		}
+
+		set_current_state(TASK_RUNNING);
 
 		if (backlog)
 			backlog->complete(backlog, -EINPROGRESS);
@@ -658,12 +669,8 @@ static int dcp_chan_thread_sha(void *data)
 			ret = dcp_sha_req_to_buf(arq);
 			fini = rctx->fini;
 			arq->complete(arq, ret);
-			if (!fini)
-				continue;
 		}
-
-		schedule();
-	} while (!kthread_should_stop());
+	}
 
 	return 0;
 }
@@ -721,9 +728,9 @@ static int dcp_sha_update_fx(struct ahash_request *req, int fini)
 		rctx->init = 1;
 	}
 
-	mutex_lock(&sdcp->mutex[actx->chan]);
+	spin_lock(&sdcp->lock[actx->chan]);
 	ret = crypto_enqueue_request(&sdcp->queue[actx->chan], &req->base);
-	mutex_unlock(&sdcp->mutex[actx->chan]);
+	spin_unlock(&sdcp->lock[actx->chan]);
 
 	wake_up_process(sdcp->thread[actx->chan]);
 	mutex_unlock(&actx->mutex);
@@ -997,7 +1004,7 @@ static int mxs_dcp_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, sdcp);
 
 	for (i = 0; i < DCP_MAX_CHANS; i++) {
-		mutex_init(&sdcp->mutex[i]);
+		spin_lock_init(&sdcp->lock[i]);
 		init_completion(&sdcp->completion[i]);
 		crypto_init_queue(&sdcp->queue[i], 50);
 	}