summaryrefslogtreecommitdiff
path: root/Documentation/ww-mutex-design.txt
diff options
context:
space:
mode:
authorKrzysztof Kozlowski <k.kozlowski@samsung.com>2014-10-13 15:34:30 +0200
committerSebastian Reichel <sre@kernel.org>2014-10-28 03:30:20 +0100
commitbdbe81445407644492b9ac69a24d35e3202d773b (patch)
tree3bd57525f83c469d8543e304925c6b056f24375f /Documentation/ww-mutex-design.txt
parentba9c91825d4a3bb49532d4a59c72e98b529b7eff (diff)
power: charger-manager: Fix accessing invalidated power supply after fuel gauge unbind
The charger manager obtained reference to fuel gauge power supply in probe with power_supply_get_by_name() for later usage. However if fuel gauge driver was removed and re-added then this reference would point to old power supply (from driver which was removed). This lead to accessing old (and probably invalid) memory which could be observed with: $ echo "12-0036" > /sys/bus/i2c/drivers/max17042/unbind $ echo "12-0036" > /sys/bus/i2c/drivers/max17042/bind $ cat /sys/devices/virtual/power_supply/battery/capacity [ 240.480084] INFO: task cat:1393 blocked for more than 120 seconds. [ 240.484799] Not tainted 3.17.0-next-20141007-00028-ge60b6dd79570 #203 [ 240.491782] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 240.499589] cat D c0469530 0 1393 1 0x00000000 [ 240.505947] [<c0469530>] (__schedule) from [<c0469d3c>] (schedule_preempt_disabled+0x14/0x20) [ 240.514449] [<c0469d3c>] (schedule_preempt_disabled) from [<c046af08>] (mutex_lock_nested+0x1bc/0x458) [ 240.523736] [<c046af08>] (mutex_lock_nested) from [<c0287a98>] (regmap_read+0x30/0x60) [ 240.531647] [<c0287a98>] (regmap_read) from [<c032238c>] (max17042_get_property+0x2e8/0x350) [ 240.540055] [<c032238c>] (max17042_get_property) from [<c03247d8>] (charger_get_property+0x264/0x348) [ 240.549252] [<c03247d8>] (charger_get_property) from [<c0320764>] (power_supply_show_property+0x48/0x1e0) [ 240.558808] [<c0320764>] (power_supply_show_property) from [<c027308c>] (dev_attr_show+0x1c/0x48) [ 240.567664] [<c027308c>] (dev_attr_show) from [<c0141fb0>] (sysfs_kf_seq_show+0x84/0x104) [ 240.575814] [<c0141fb0>] (sysfs_kf_seq_show) from [<c0140b18>] (kernfs_seq_show+0x24/0x28) [ 240.584061] [<c0140b18>] (kernfs_seq_show) from [<c0104574>] (seq_read+0x1b0/0x484) [ 240.591702] [<c0104574>] (seq_read) from [<c00e1e24>] (vfs_read+0x88/0x144) [ 240.598640] [<c00e1e24>] (vfs_read) from [<c00e1f20>] (SyS_read+0x40/0x8c) [ 240.605507] [<c00e1f20>] (SyS_read) from [<c000e760>] (ret_fast_syscall+0x0/0x48) [ 240.612952] 4 locks held by cat/1393: [ 240.616589] #0: (&p->lock){+.+.+.}, at: [<c01043f4>] seq_read+0x30/0x484 [ 240.623414] #1: (&of->mutex){+.+.+.}, at: [<c01417dc>] kernfs_seq_start+0x1c/0x8c [ 240.631086] #2: (s_active#31){++++.+}, at: [<c01417e4>] kernfs_seq_start+0x24/0x8c [ 240.638777] #3: (&map->mutex){+.+...}, at: [<c0287a98>] regmap_read+0x30/0x60 The charger-manager should get reference to fuel gauge power supply on each use of get_property callback. The thermal zone 'tzd' field of power supply should not be used because of the same reason. Additionally this change solves also the issue with nested thermal_zone_get_temp() calls and related false lockdep positive for deadlock for thermal zone's mutex [1]. When fuel gauge is used as source of temperature then the charger manager forwards its get_temp calls to fuel gauge thermal zone. So actually different mutexes are used (one for charger manager thermal zone and second for fuel gauge thermal zone) but for lockdep this is one class of mutex. The recursion is removed by retrieving temperature through power supply's get_property(). In case external thermal zone is used ('cm-thermal-zone' property is present in DTS) the recursion does not exist. Charger manager simply exports POWER_SUPPLY_PROP_TEMP_AMBIENT property (instead of POWER_SUPPLY_PROP_TEMP) thus no thermal zone is created for this power supply. [1] https://lkml.org/lkml/2014/10/6/309 Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> Cc: <stable@vger.kernel.org> Fixes: 3bb3dbbd56ea ("power_supply: Add initial Charger-Manager driver") Signed-off-by: Sebastian Reichel <sre@kernel.org>
Diffstat (limited to 'Documentation/ww-mutex-design.txt')
0 files changed, 0 insertions, 0 deletions