[PATCH] mtd: lpddr: Fix a potential double mutex_lock

[Christophe JAILLET]

If 'chip->state == FL_SYNCING', we will 'goto retry' with the mutex
'&shared->lock' already taken.
In such a case, the 'mutex_lock' at line 927 can never succeed.

In order to avoid a deadlock, move the 'mutex_lock(&shared->lock)' at the
very end of the block.

This has been spotted with the following coccinelle script:

@find@
expression x, t;
@@

        mutex_lock(x);
        ... when != mutex_unlock(x)
        mutex_lock(t);

@@
expression find.t;
expression find.x;
@@

*       mutex_lock(t);
        ... when != mutex_unlock(t)
*       mutex_lock(x);


Fixes:  c68264711ca6 ("[MTD] LPDDR Command set driver")
Signed-off-by: Christophe JAILLET <christophe.jail...@wanadoo.fr>
---
Review carefuly, untested.
---
 drivers/mtd/lpddr/lpddr_cmds.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/lpddr/lpddr_cmds.c b/drivers/mtd/lpddr/lpddr_cmds.c
index 018c75faadb3..830dd0855ab3 100644
--- a/drivers/mtd/lpddr/lpddr_cmds.c
+++ b/drivers/mtd/lpddr/lpddr_cmds.c
@@ -237,7 +237,6 @@ static int get_chip(struct map_info *map, struct flchip 
*chip, int mode)
                                mutex_unlock(&contender->mutex);
                                return ret;
                        }
-                       mutex_lock(&shared->lock);
 
                        /* We should not own chip if it is already in FL_SYNCING
                         * state. Put contender and retry. */
@@ -247,6 +246,8 @@ static int get_chip(struct map_info *map, struct flchip 
*chip, int mode)
                                goto retry;
                        }
                        mutex_unlock(&contender->mutex);
+
+                       mutex_lock(&shared->lock);
                }
 
                /* Check if we have suspended erase on this chip.
-- 
2.14.1