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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
        Corentin Labbe <clabbe@baylibre.com>,
        Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 120/171] dma-debug: add a schedule point in debug_dma_dump_mappings()
Date:   Thu,  2 Jan 2020 23:07:31 +0100
Message-Id: <20200102220603.732883004@linuxfoundation.org>
In-Reply-To: <20200102220546.960200039@linuxfoundation.org>
References: <20200102220546.960200039@linuxfoundation.org>
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From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 9ff6aa027dbb98755f0265695354f2dd07c0d1ce ]

debug_dma_dump_mappings() can take a lot of cpu cycles :

lpk43:/# time wc -l /sys/kernel/debug/dma-api/dump
163435 /sys/kernel/debug/dma-api/dump

real	0m0.463s
user	0m0.003s
sys	0m0.459s

Let's add a cond_resched() to avoid holding cpu for too long.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Corentin Labbe <clabbe@baylibre.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 lib/dma-debug.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 8971370bfb16..4435bec55fb5 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -435,6 +435,7 @@ void debug_dma_dump_mappings(struct device *dev)
 		}
 
 		spin_unlock_irqrestore(&bucket->lock, flags);
+		cond_resched();
 	}
 }
 EXPORT_SYMBOL(debug_dma_dump_mappings);
-- 
2.20.1