linux-kernel - [PATCH V1] Fix Regmap Block Write single-rw Mutex Deadlock

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Message-ID: <201310091646.r99Gk3N9015896@swsrvapps-02.lan>
Date:	Wed, 9 Oct 2013 17:44:38 +0100
From:	Anthony Olech <anthony.olech.opensource@...semi.com>
To:	Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	David Dajun Chen <david.chen@...semi.com>
Subject: [PATCH V1] Fix Regmap Block Write single-rw Mutex Deadlock

This patch is relative to linux-next repository tag next-20130927

When regmap_bulk_write() is called with the map->use_single_rw flag set
an immediate mutex deadlock happens because regmap_raw_write() is called
after obtaining the mutex and regmap_raw_write() itself then tries to
obtain the mutex as well.

It is obvious that no one other than myself tried it with a real device.
I did, but only for the purposes of an experiment and demonstration.

But even if this situation will never ever happen with a real device, it
is a bug and therefore should be fixed.

Signed-off-by: Anthony Olech <anthony.olech.opensource@...semi.com>
---
 drivers/base/regmap/regmap.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 00152bf..6bd9294 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1488,10 +1488,11 @@ int regmap_bulk_write(struct regmap *map, unsigned int reg, const void *val,
 	 */
 	if (map->use_single_rw) {
 		for (i = 0; i < val_count; i++) {
-			ret = regmap_raw_write(map,
-					       reg + (i * map->reg_stride),
-					       val + (i * val_bytes),
-					       val_bytes);
+			ret = _regmap_raw_write(map,
+						reg + (i * map->reg_stride),
+						val + (i * val_bytes),
+						val_bytes,
+						false);
 			if (ret != 0)
 				return ret;
 		}
-- 
end-of-patch for Fix Regmap Block Write single-rw Mutex Deadlock V1

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