linux-kernel - [PATCH] dma-debug: add a schedule point in debug_dma_dump

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Date:   Mon, 28 Oct 2019 14:56:46 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Corentin Labbe <clabbe@...libre.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: [PATCH] dma-debug: add a schedule point in debug_dma_dump_mappings()

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>
---
 kernel/dma/debug.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 099002d84f466af0a8e421d035ac8eb119e08bd8..4ad74f5987ea9e95f9bb5e2d1592254e367d24fb 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -420,6 +420,7 @@ void debug_dma_dump_mappings(struct device *dev)
 		}
 
 		spin_unlock_irqrestore(&bucket->lock, flags);
+		cond_resched();
 	}
 }
 
-- 
2.24.0.rc0.303.g954a862665-goog