linux-kernel - Applied "regmap: fix deadlock on _regmap_raw

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Message-Id: <E1bn1BY-0002KH-Oz@debutante>
Date:   Thu, 22 Sep 2016 11:24:56 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Nikita Yushchenko <nikita.yoush@...entembedded.com>
Cc:     Mark Brown <broonie@...nel.org>, Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Xiubo Li <lixiubo@...s.chinamobile.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Jon Ringle <jringle@...dpoint.com>,
        Chen-Yu Tsai <wens@...e.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, Chris Healy <cphealy@...il.com>
Subject: Applied "regmap: fix deadlock on _regmap_raw_write() error path" to the regmap tree

The patch

   regmap: fix deadlock on _regmap_raw_write() error path

has been applied to the regmap tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From f0aa1ce6259eb65f53f969b3250c1d0aac84f30b Mon Sep 17 00:00:00 2001
From: Nikita Yushchenko <nikita.yoush@...entembedded.com>
Date: Thu, 22 Sep 2016 12:02:25 +0300
Subject: [PATCH] regmap: fix deadlock on _regmap_raw_write() error path

Commit 815806e39bf6 ("regmap: drop cache if the bus transfer error")
added a call to regcache_drop_region() to error path in
_regmap_raw_write(). However that path runs with regmap lock taken,
and regcache_drop_region() tries to re-take it, causing a deadlock.
Fix that by calling map->cache_ops->drop() directly.

Signed-off-by: Nikita Yushchenko <nikita.yoush@...entembedded.com>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 drivers/base/regmap/regmap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 25d26bb18970..e964d068874d 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1475,7 +1475,11 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,

 		kfree(buf);
 	} else if (ret != 0 && !map->cache_bypass && map->format.parse_val) {
-		regcache_drop_region(map, reg, reg + 1);
+		/* regcache_drop_region() takes lock that we already have,
+		 * thus call map->cache_ops->drop() directly
+		 */
+		if (map->cache_ops && map->cache_ops->drop)
+			map->cache_ops->drop(map, reg, reg + 1);
 	}

 	trace_regmap_hw_write_done(map, reg, val_len / map->format.val_bytes);
-- 
2.8.1