linux-kernel - [PATCH 6/6] dmaengine: at_hdmac: fix race while monitoring channel status

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Message-Id: <1294843150-6962-5-git-send-email-nicolas.ferre@atmel.com>
Date:	Wed, 12 Jan 2011 15:39:10 +0100
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	dan.j.williams@...el.com, linux-arm-kernel@...ts.infradead.org
Cc:	linux-kernel@...r.kernel.org, hong.xu@...el.com,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: [PATCH 6/6] dmaengine: at_hdmac: fix race while monitoring channel status

We were reading channel status then taking a lock. This lead to a race because
this lock may delay us and then make this channel not idle anymore.

Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
---
 drivers/dma/at_hdmac.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index 99942a5..3d7d705 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -853,11 +853,11 @@ static void atc_issue_pending(struct dma_chan *chan)
 
 	dev_vdbg(chan2dev(chan), "issue_pending\n");
 
+	spin_lock_bh(&atchan->lock);
 	if (!atc_chan_is_enabled(atchan)) {
-		spin_lock_bh(&atchan->lock);
 		atc_advance_work(atchan);
-		spin_unlock_bh(&atchan->lock);
 	}
+	spin_unlock_bh(&atchan->lock);
 }
 
 /**
-- 
1.7.3

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