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Subject[PATCH] w1: Introduce a slave mutex for serializing IO.

w1 devices need a mutex to serial IO.
Most use master->mutex.

However that is used for other purposes and they can conflict.

In particular master->mutex is held while w1_attach_slave_device is
called.

For bq27000, this registers a 'powersupply' device which tries to
read the current status. The attempt to read will cause a deadlock on
master->mutex.

So create a new per-slave mutex and use that for serializing IO for
bq27000.

Signed-off-by: NeilBrown <neilb@suse.de>
---
drivers/w1/slaves/w1_bq27000.c | 4 ++--
drivers/w1/w1.c | 1 +
drivers/w1/w1.h | 1 +
3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/w1/slaves/w1_bq27000.c b/drivers/w1/slaves/w1_bq27000.c
index 52ad812..8755478 100644
--- a/drivers/w1/slaves/w1_bq27000.c
+++ b/drivers/w1/slaves/w1_bq27000.c
@@ -31,10 +31,10 @@ static int w1_bq27000_read(struct device *dev, unsigned int reg)
u8 val;
struct w1_slave *sl = container_of(dev->parent, struct w1_slave, dev);

- mutex_lock(&sl->master->mutex);
+ mutex_lock(&sl->mutex);
w1_write_8(sl->master, HDQ_CMD_READ | reg);
val = w1_read_8(sl->master);
- mutex_unlock(&sl->master->mutex);
+ mutex_unlock(&sl->mutex);

return val;
}
diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index 9761950..2173f83 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -688,6 +688,7 @@ static int w1_attach_slave_device(struct w1_master *dev, struct w1_reg_num *rn)
memcpy(&sl->reg_num, rn, sizeof(sl->reg_num));
atomic_set(&sl->refcnt, 0);
init_completion(&sl->released);
+ mutex_init(&sl->mutex);

spin_lock(&w1_flock);
f = w1_family_registered(rn->family);
diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index 4d012ca..8c8be38 100644
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -75,6 +75,7 @@ struct w1_slave
void *family_data;
struct device dev;
struct completion released;
+ struct mutex mutex;
};

typedef void (*w1_slave_found_callback)(struct w1_master *, u64);
--
1.7.10
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