Re: [PATCH] Battery: sysfs_remove_battery(): possible circularlocking

From: Sergey Senozhatsky
Date: Fri Aug 05 2011 - 03:22:03 EST

On (08/05/11 13:10), lan,Tianyu wrote:
> I think changing 'the marker' to 'battery->bat.name' will introduce
> problem.
> In the sysfs_add_battery(), when the 'battery->bat.name' is assigned,
> the power_supply_register() and device_create_file() have not been
> invoked. In this time, maybe sysfs_remove_battery() will be invoked and
> cause device_remove_file() and power_supply_unregister() invoked without
> device file created and power supply registered.
>

Hm, good point! It was ~3.30AM when I was writing the patch, so I
obviously didn't think carefully enought. Here the whole trace (I'll
get back to my laptop within 2 hours):

[14818.477168]
[14818.477170] =======================================================
[14818.477200] [ INFO: possible circular locking dependency detected ]
[14818.477221] 3.1.0-dbg-07865-g1280ea8-dirty #668
[14818.477236] -------------------------------------------------------
[14818.477257] s2ram/1599 is trying to acquire lock:
[14818.477276] (s_active#8){++++.+}, at: [<ffffffff81169147>] sysfs_addrm_finish+0x31/0x5a
[14818.477323]
[14818.477325] but task is already holding lock:
[14818.477350] (&battery->lock){+.+.+.}, at: [<ffffffffa0047278>] sysfs_remove_battery+0x10/0x4b [battery]
[14818.477395]
[14818.477397] which lock already depends on the new lock.
[14818.477399]
[14818.477433]
[14818.477435] the existing dependency chain (in reverse order) is:
[14818.477461]
[14818.477463] -> #1 (&battery->lock){+.+.+.}:
[14818.477497] [<ffffffff810718d2>] lock_acquire+0x138/0x1ac
[14818.477527] [<ffffffff8148b303>] mutex_lock_nested+0x5e/0x325
[14818.477558] [<ffffffffa00473bf>] acpi_battery_get_state+0x6a/0x16f [battery]
[14818.477592] [<ffffffffa00474f1>] acpi_battery_get_property+0x2d/0x1cf [battery]
[14818.477627] [<ffffffff813c7348>] power_supply_show_property+0x59/0x147
[14818.477662] [<ffffffff813c74fc>] power_supply_uevent+0x93/0x17f
[14818.477692] [<ffffffff81386f96>] dev_uevent+0x12f/0x155
[14818.477722] [<ffffffff813858b8>] show_uevent+0xa9/0xf4
[14818.477750] [<ffffffff81385d02>] dev_attr_show+0x22/0x49
[14818.477779] [<ffffffff81168690>] sysfs_read_file+0xb4/0x139
[14818.477809] [<ffffffff81109171>] vfs_read+0xaa/0x13a
[14818.477840] [<ffffffff81109246>] sys_read+0x45/0x6c
[14818.477867] [<ffffffff81492f92>] system_call_fastpath+0x16/0x1b
[14818.477899]
[14818.477900] -> #0 (s_active#8){++++.+}:
[14818.477938] [<ffffffff81070cb5>] __lock_acquire+0xfe4/0x164b
[14818.477968] [<ffffffff810718d2>] lock_acquire+0x138/0x1ac
[14818.477997] [<ffffffff81168a79>] sysfs_deactivate+0x9b/0xec
[14818.478026] [<ffffffff81169147>] sysfs_addrm_finish+0x31/0x5a
[14818.478055] [<ffffffff81167bc5>] sysfs_hash_and_remove+0x54/0x77
[14818.478086] [<ffffffff811681b9>] sysfs_remove_file+0x12/0x14
[14818.478115] [<ffffffff81385bf8>] device_remove_file+0x12/0x14
[14818.478145] [<ffffffff81386504>] device_del+0x119/0x17c
[14818.478172] [<ffffffff81386575>] device_unregister+0xe/0x1a
[14818.478201] [<ffffffff813c6ef9>] power_supply_unregister+0x23/0x27
[14818.478233] [<ffffffffa004729c>] sysfs_remove_battery+0x34/0x4b [battery]
[14818.478267] [<ffffffffa004778f>] battery_notify+0x2c/0x3a [battery]
[14818.478299] [<ffffffff8148fe82>] notifier_call_chain+0x74/0xa1
[14818.478330] [<ffffffff810624b4>] __blocking_notifier_call_chain+0x6c/0x89
[14818.478363] [<ffffffff810624e0>] blocking_notifier_call_chain+0xf/0x11
[14818.478394] [<ffffffff8107e40e>] pm_notifier_call_chain+0x15/0x27
[14818.478426] [<ffffffff8107ee1a>] enter_state+0xa7/0xd5
[14818.478454] [<ffffffff8107e341>] state_store+0xaa/0xc0
[14818.478482] [<ffffffff81248837>] kobj_attr_store+0x17/0x19
[14818.478511] [<ffffffff81167e27>] sysfs_write_file+0x103/0x13f
[14818.478541] [<ffffffff81109037>] vfs_write+0xad/0x13d
[14818.478568] [<ffffffff811092b2>] sys_write+0x45/0x6c
[14818.478595] [<ffffffff81492f92>] system_call_fastpath+0x16/0x1b
[14818.478626]
[14818.478628] other info that might help us debug this:
[14818.478630]
[14818.478665] Possible unsafe locking scenario:
[14818.478668]
[14818.478694] CPU0 CPU1
[14818.478713] ---- ----
[14818.478731] lock(&battery->lock);
[14818.478754] lock(s_active);
[14818.478782] lock(&battery->lock);
[14818.478810] lock(s_active);
[14818.478831]
[14818.478832] *** DEADLOCK ***
[14818.478835]
[14818.478868] 5 locks held by s2ram/1599:
[14818.478885] #0: (&buffer->mutex){+.+.+.}, at: [<ffffffff81167d5b>] sysfs_write_file+0x37/0x13f
[14818.478932] #1: (s_active#106){.+.+.+}, at: [<ffffffff81167e06>] sysfs_write_file+0xe2/0x13f
[14818.478980] #2: (pm_mutex){+.+...}, at: [<ffffffff8107ed9d>] enter_state+0x2a/0xd5
[14818.479021] #3: ((pm_chain_head).rwsem){++++..}, at: [<ffffffff8106249f>] __blocking_notifier_call_chain+0x57/0x89
[14818.479070] #4: (&battery->lock){+.+.+.}, at: [<ffffffffa0047278>] sysfs_remove_battery+0x10/0x4b [battery]
[14818.479119]
[14818.479121] stack backtrace:
[14818.479148] Pid: 1599, comm: s2ram Not tainted 3.1.0-dbg-07865-g1280ea8-dirty #668
[14818.479175] Call Trace:
[14818.479198] [<ffffffff814828c3>] print_circular_bug+0x293/0x2a4
[14818.479228] [<ffffffff81070cb5>] __lock_acquire+0xfe4/0x164b
[14818.479260] [<ffffffff81169147>] ? sysfs_addrm_finish+0x31/0x5a
[14818.479288] [<ffffffff810718d2>] lock_acquire+0x138/0x1ac
[14818.479316] [<ffffffff81169147>] ? sysfs_addrm_finish+0x31/0x5a
[14818.479345] [<ffffffff81168a79>] sysfs_deactivate+0x9b/0xec
[14818.479373] [<ffffffff81169147>] ? sysfs_addrm_finish+0x31/0x5a
[14818.479405] [<ffffffff81169147>] sysfs_addrm_finish+0x31/0x5a
[14818.479433] [<ffffffff81167bc5>] sysfs_hash_and_remove+0x54/0x77
[14818.479461] [<ffffffff811681b9>] sysfs_remove_file+0x12/0x14
[14818.479488] [<ffffffff81385bf8>] device_remove_file+0x12/0x14
[14818.479516] [<ffffffff81386504>] device_del+0x119/0x17c
[14818.479542] [<ffffffff81386575>] device_unregister+0xe/0x1a
[14818.479570] [<ffffffff813c6ef9>] power_supply_unregister+0x23/0x27
[14818.479601] [<ffffffffa004729c>] sysfs_remove_battery+0x34/0x4b [battery]
[14818.479632] [<ffffffffa004778f>] battery_notify+0x2c/0x3a [battery]
[14818.479662] [<ffffffff8148fe82>] notifier_call_chain+0x74/0xa1
[14818.479692] [<ffffffff810624b4>] __blocking_notifier_call_chain+0x6c/0x89
[14818.479722] [<ffffffff810624e0>] blocking_notifier_call_chain+0xf/0x11
[14818.479751] [<ffffffff8107e40e>] pm_notifier_call_chain+0x15/0x27
[14818.479770] [<ffffffff8107ee1a>] enter_state+0xa7/0xd5
[14818.479782] [<ffffffff8107e341>] state_store+0xaa/0xc0
[14818.479795] [<ffffffff8107e297>] ? pm_async_store+0x45/0x45
[14818.479807] [<ffffffff81248837>] kobj_attr_store+0x17/0x19
[14818.479820] [<ffffffff81167e27>] sysfs_write_file+0x103/0x13f
[14818.479834] [<ffffffff81109037>] vfs_write+0xad/0x13d
[14818.479847] [<ffffffff811092b2>] sys_write+0x45/0x6c
[14818.479860] [<ffffffff81492f92>] system_call_fastpath+0x16/0x1b


Sergey






> sysfs_remove_battery() will be invoked in the battery_notify(),
> acpi_battery_refresh() and sysfs_remove_battery() which causes the
> situation. This is also the cause of bug 35642.
>
> > I've changed `the marker' from `battery->bat.dev' to `battery->bat.name', so
> > the basic idea should remain the same, now we just can release battery->lock
> > more quicker, before device_remove_file() call.
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> >
> > ---
> >
> > drivers/acpi/battery.c | 6 ++++--
> > 1 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> > index 87c0a8d..398cbfb 100644
> > --- a/drivers/acpi/battery.c
> > +++ b/drivers/acpi/battery.c
> > @@ -574,15 +574,17 @@ static int sysfs_add_battery(struct acpi_battery *battery)
> > static void sysfs_remove_battery(struct acpi_battery *battery)
> > {
> > mutex_lock(&battery->lock);
> > - if (!battery->bat.dev) {
> > + if (!battery->bat.name) {
> > mutex_unlock(&battery->lock);
> > return;
> > }
> >
> > + battery->bat.name = NULL;
> > + mutex_unlock(&battery->lock);
> > +
> > device_remove_file(battery->bat.dev, &alarm_attr);
> > power_supply_unregister(&battery->bat);
> > battery->bat.dev = NULL;
> > - mutex_unlock(&battery->lock);
> > }
> >
> > /*
> >
>
>
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