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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_battery.c which calls them. Signed-off-by: NeilBrown <firstname.lastname@example.org> Acked-by: Evgeniy Polyakov <email@example.com> Signed-off-by: Greg Kroah-Hartman <firstname.lastname@example.org>
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Showing with 57 additions and 95 deletions.
- +1 −10 drivers/power/ds2780_battery.c
- +1 −11 drivers/power/ds2781_battery.c
- +4 −0 drivers/w1/masters/ds1wm.c
- +2 −2 drivers/w1/slaves/w1_bq27000.c
- +12 −12 drivers/w1/slaves/w1_ds2408.c
- +2 −2 drivers/w1/slaves/w1_ds2423.c
- +4 −4 drivers/w1/slaves/w1_ds2431.c
- +4 −4 drivers/w1/slaves/w1_ds2433.c
- +4 −4 drivers/w1/slaves/w1_ds2760.c
- +4 −18 drivers/w1/slaves/w1_ds2780.c
- +0 −2 drivers/w1/slaves/w1_ds2780.h
- +4 −18 drivers/w1/slaves/w1_ds2781.c
- +0 −2 drivers/w1/slaves/w1_ds2781.h
- +5 −5 drivers/w1/slaves/w1_therm.c
- +8 −1 drivers/w1/w1.c
- +1 −0 drivers/w1/w1.h
- +1 −0 drivers/w1/w1_int.c
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