Commit Graph

8 Commits

Author SHA1 Message Date
NeilBrown b02f8bede2 W1: split master mutex to avoid deadlocks.
The 'mutex' in struct w1_master is use for two very different
purposes.

Firstly it protects various data structures such as the list of all
slaves.

Secondly it protects the w1 buss against concurrent accesses.

This can lead to deadlocks when the ->probe code called while adding a
slave needs to talk on the bus, as is the case for power_supply
devices.
ds2780 and ds2781 drivers contain a work around to track which
process hold the lock simply to avoid this deadlock.  bq27000 doesn't
have that work around and so deadlocks.

There are other possible deadlocks involving sysfs.
When removing a device the sysfs s_active lock is held, so the lock
that protects the slave list must take precedence over s_active.
However when access power_supply attributes via sysfs, the s_active
lock must take precedence over the lock that protects accesses to
the bus.

So to avoid deadlocks between w1 slaves and sysfs, these must be
two separate locks.  Making them separate means that the work around
in ds2780 and ds2781 can be removed.

So this patch:
 - adds a new mutex: "bus_mutex" which serialises access to the bus.
 - takes in mutex in w1_search and ds1wm_search while they access
   the bus for searching.  The mutex is dropped before calling the
   callback which adds the slave.
 - changes all slaves to use bus_mutex instead of mutex to
   protect access to the bus
 - removes w1_ds2790_io_nolock and w1_ds2781_io_nolock, and the
   related code from drivers/power/ds278[01]_battery.c which
   calls them.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-13 16:38:40 -07:00
Greg Kroah-Hartman dd0aa67cd7 Revert "w1: introduce a slave mutex for serializing IO"
This reverts commit 59d4467be4.

Turns out it was the wrong version, will apply the correct version after
this.

Reported-by: NeilBrown <neilb@suse.de>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-13 16:33:54 -07:00
NeilBrown 59d4467be4 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>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-12 15:27:32 -07:00
NeilBrown f6e8a1d7b4 w1_bq27000: Only one thread can access the bq27000 at a time.
If multiple threads try, they trip over each other badly.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-02-24 14:25:50 -08:00
NeilBrown df7019f370 w1_bq27000 - remove w1_bq27000_write
The function is never used so remove it to avoid bit-rot.
It can trivially be re-added if there is ever a need.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-02-24 14:25:50 -08:00
NeilBrown b6c40b8581 w1_bq27000: remove unnecessary NULL test.
As recent change means that we now dereference 'dev' before testing
for NULL.

That means either the change was wrong, or the test isn't needed.
As this function is only called from one driver (bq27x000_battery) and
it always passed a non-NULL dev, it seems good to assume that the
test isn't needed.

So remove it.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-02-24 14:25:50 -08:00
NeilBrown 9f3519d2ed w1: Fix w1_bq27000
w1_bq27000 adds a bq27000-battery platform device but does not provide
platform data for it. This causes the bq27x00 driver to dereference a NULL
pointer.
So provide the appropriate platform data.  This requires modifying
w1_bq27000_read so that it find the w1 device as the parent of the bq device.

Also there is no point exporting w1_bq27000_read as nothing else uses it
or could use it.  So make it static.

Finally, as there is no way to track how many batteries have been found, and
we will probably only find one, use an id number of '-1' to assert that this
is a unique instance.

Signed-off-by: NeilBrown <neilb@suse.de>
Tested-by: Thomas Weber <weber@corscience.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-02-15 17:17:50 -08:00
Madhusudhan Chikkature cfbc619033 hdq: bQ27000 HDQ Slave Interface Driver
Provide the BQ27000 slave interface driver.

Signed-off-by: Madhusudhan Chikkature<madhu.cr@ti.com>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-11-12 17:17:18 -08:00