linux-kernel - [PATCH 4.4 098/137] dma-debug: add a schedule point in debug_dma_dump

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Date:   Thu,  2 Jan 2020 23:07:51 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Corentin Labbe <clabbe@...libre.com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 098/137] dma-debug: add a schedule point in debug_dma_dump_mappings()

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

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 51a76af25c66..173013f5e41b 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -427,6 +427,7 @@ 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