linux-kernel - [PATCH v2 02/16] dmaengine: bcm-sba-raid: Reduce locking context in sba_alloc

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Message-Id: <1501583880-32072-3-git-send-email-anup.patel@broadcom.com>
Date:   Tue,  1 Aug 2017 16:07:46 +0530
From:   Anup Patel <anup.patel@...adcom.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Vinod Koul <vinod.koul@...el.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Scott Branden <sbranden@...adcom.com>,
        Ray Jui <rjui@...adcom.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        dmaengine@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        Anup Patel <anup.patel@...adcom.com>
Subject: [PATCH v2 02/16] dmaengine: bcm-sba-raid: Reduce locking context in sba_alloc_request()

We don't require to hold "sba->reqs_lock" for long-time
in sba_alloc_request() because lock protection is not
required when initializing members of "struct sba_request".

Signed-off-by: Anup Patel <anup.patel@...adcom.com>
---
 drivers/dma/bcm-sba-raid.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/dma/bcm-sba-raid.c b/drivers/dma/bcm-sba-raid.c
index 76999b7..f81d5ac 100644
--- a/drivers/dma/bcm-sba-raid.c
+++ b/drivers/dma/bcm-sba-raid.c
@@ -207,24 +207,24 @@ static struct sba_request *sba_alloc_request(struct sba_device *sba)
 	struct sba_request *req = NULL;
 
 	spin_lock_irqsave(&sba->reqs_lock, flags);
-
 	req = list_first_entry_or_null(&sba->reqs_free_list,
 				       struct sba_request, node);
 	if (req) {
 		list_move_tail(&req->node, &sba->reqs_alloc_list);
-		req->state = SBA_REQUEST_STATE_ALLOCED;
-		req->fence = false;
-		req->first = req;
-		INIT_LIST_HEAD(&req->next);
-		req->next_count = 1;
-		atomic_set(&req->next_pending_count, 1);
-
 		sba->reqs_free_count--;
-
-		dma_async_tx_descriptor_init(&req->tx, &sba->dma_chan);
 	}
-
 	spin_unlock_irqrestore(&sba->reqs_lock, flags);
+	if (!req)
+		return NULL;
+
+	req->state = SBA_REQUEST_STATE_ALLOCED;
+	req->fence = false;
+	req->first = req;
+	INIT_LIST_HEAD(&req->next);
+	req->next_count = 1;
+	atomic_set(&req->next_pending_count, 1);
+
+	dma_async_tx_descriptor_init(&req->tx, &sba->dma_chan);
 
 	return req;
 }
-- 
2.7.4