[PATCH] device: separate all subsys mutexes
From: Michal Hocko
Date: Tue Mar 12 2013 - 12:18:28 EST
ca22e56d (driver-core: implement 'sysdev' functionality for regular
devices and buses) has introduced bus_register macro with a static
key to distinguish different subsys mutex classes.
This however doesn't work for different subsys which use a common
registering function. One example is subsys_system_register (and
mce_device and cpu_device).
In the end this leads to the following lockdep splat:
[ 207.271924] ======================================================
[ 207.271932] [ INFO: possible circular locking dependency detected ]
[ 207.271942] 3.9.0-rc1-0.7-default+ #34 Not tainted
[ 207.271948] -------------------------------------------------------
[ 207.271957] bash/10493 is trying to acquire lock:
[ 207.271963] (subsys mutex){+.+.+.}, at: [<ffffffff8134af27>] bus_remove_device+0x37/0x1c0
[ 207.271987]
[ 207.271987] but task is already holding lock:
[ 207.271995] (cpu_hotplug.lock){+.+.+.}, at: [<ffffffff81046ccf>] cpu_hotplug_begin+0x2f/0x60
[ 207.272012]
[ 207.272012] which lock already depends on the new lock.
[ 207.272012]
[ 207.272023]
[ 207.272023] the existing dependency chain (in reverse order) is:
[ 207.272033]
[ 207.272033] -> #4 (cpu_hotplug.lock){+.+.+.}:
[ 207.272044] [<ffffffff810ae329>] lock_acquire+0xe9/0x120
[ 207.272056] [<ffffffff814ad807>] mutex_lock_nested+0x37/0x360
[ 207.272069] [<ffffffff81046ba9>] get_online_cpus+0x29/0x40
[ 207.272082] [<ffffffff81185210>] drain_all_stock+0x30/0x150
[ 207.272094] [<ffffffff811853da>] mem_cgroup_reclaim+0xaa/0xe0
[ 207.272104] [<ffffffff8118775e>] __mem_cgroup_try_charge+0x51e/0xcf0
[ 207.272114] [<ffffffff81188486>] mem_cgroup_charge_common+0x36/0x60
[ 207.272125] [<ffffffff811884da>] mem_cgroup_newpage_charge+0x2a/0x30
[ 207.272135] [<ffffffff81150531>] do_wp_page+0x231/0x830
[ 207.272147] [<ffffffff8115151e>] handle_pte_fault+0x19e/0x8d0
[ 207.272157] [<ffffffff81151da8>] handle_mm_fault+0x158/0x1e0
[ 207.272166] [<ffffffff814b6153>] do_page_fault+0x2a3/0x4e0
[ 207.272178] [<ffffffff814b2578>] page_fault+0x28/0x30
[ 207.272189]
[ 207.272189] -> #3 (&mm->mmap_sem){++++++}:
[ 207.272199] [<ffffffff810ae329>] lock_acquire+0xe9/0x120
[ 207.272208] [<ffffffff8114c5ad>] might_fault+0x6d/0x90
[ 207.272218] [<ffffffff811a11e3>] filldir64+0xb3/0x120
[ 207.272229] [<ffffffffa013fc19>] call_filldir+0x89/0x130 [ext3]
[ 207.272248] [<ffffffffa0140377>] ext3_readdir+0x6b7/0x7e0 [ext3]
[ 207.272263] [<ffffffff811a1519>] vfs_readdir+0xa9/0xc0
[ 207.272273] [<ffffffff811a15cb>] sys_getdents64+0x9b/0x110
[ 207.272284] [<ffffffff814bb599>] system_call_fastpath+0x16/0x1b
[ 207.272296]
[ 207.272296] -> #2 (&type->i_mutex_dir_key#3){+.+.+.}:
[ 207.272309] [<ffffffff810ae329>] lock_acquire+0xe9/0x120
[ 207.272319] [<ffffffff814ad807>] mutex_lock_nested+0x37/0x360
[ 207.272329] [<ffffffff8119c254>] link_path_walk+0x6f4/0x9a0
[ 207.272339] [<ffffffff8119e7fa>] path_openat+0xba/0x470
[ 207.272349] [<ffffffff8119ecf8>] do_filp_open+0x48/0xa0
[ 207.272358] [<ffffffff8118d81c>] file_open_name+0xdc/0x110
[ 207.272369] [<ffffffff8118d885>] filp_open+0x35/0x40
[ 207.272378] [<ffffffff8135c76e>] _request_firmware+0x52e/0xb20
[ 207.272389] [<ffffffff8135cdd6>] request_firmware+0x16/0x20
[ 207.272399] [<ffffffffa03bdb91>] request_microcode_fw+0x61/0xd0 [microcode]
[ 207.272416] [<ffffffffa03bd554>] microcode_init_cpu+0x104/0x150 [microcode]
[ 207.272431] [<ffffffffa03bd61c>] mc_device_add+0x7c/0xb0 [microcode]
[ 207.272444] [<ffffffff8134a419>] subsys_interface_register+0xc9/0x100
[ 207.272457] [<ffffffffa04fc0f4>] 0xffffffffa04fc0f4
[ 207.272472] [<ffffffff81000202>] do_one_initcall+0x42/0x180
[ 207.272485] [<ffffffff810bbeff>] load_module+0x19df/0x1b70
[ 207.272499] [<ffffffff810bc376>] sys_init_module+0xe6/0x130
[ 207.272511] [<ffffffff814bb599>] system_call_fastpath+0x16/0x1b
[ 207.272523]
[ 207.272523] -> #1 (umhelper_sem){++++.+}:
[ 207.272537] [<ffffffff810ae329>] lock_acquire+0xe9/0x120
[ 207.272548] [<ffffffff814ae9c4>] down_read+0x34/0x50
[ 207.272559] [<ffffffff81062bff>] usermodehelper_read_trylock+0x4f/0x100
[ 207.272575] [<ffffffff8135c7dd>] _request_firmware+0x59d/0xb20
[ 207.272587] [<ffffffff8135cdd6>] request_firmware+0x16/0x20
[ 207.272599] [<ffffffffa03bdb91>] request_microcode_fw+0x61/0xd0 [microcode]
[ 207.272613] [<ffffffffa03bd554>] microcode_init_cpu+0x104/0x150 [microcode]
[ 207.272627] [<ffffffffa03bd61c>] mc_device_add+0x7c/0xb0 [microcode]
[ 207.272641] [<ffffffff8134a419>] subsys_interface_register+0xc9/0x100
[ 207.272654] [<ffffffffa04fc0f4>] 0xffffffffa04fc0f4
[ 207.272666] [<ffffffff81000202>] do_one_initcall+0x42/0x180
[ 207.272678] [<ffffffff810bbeff>] load_module+0x19df/0x1b70
[ 207.272690] [<ffffffff810bc376>] sys_init_module+0xe6/0x130
[ 207.272702] [<ffffffff814bb599>] system_call_fastpath+0x16/0x1b
[ 207.272715]
[ 207.272715] -> #0 (subsys mutex){+.+.+.}:
[ 207.272729] [<ffffffff810ae002>] __lock_acquire+0x13b2/0x15f0
[ 207.272740] [<ffffffff810ae329>] lock_acquire+0xe9/0x120
[ 207.272751] [<ffffffff814ad807>] mutex_lock_nested+0x37/0x360
[ 207.272763] [<ffffffff8134af27>] bus_remove_device+0x37/0x1c0
[ 207.272775] [<ffffffff81349114>] device_del+0x134/0x1f0
[ 207.272786] [<ffffffff813491f2>] device_unregister+0x22/0x60
[ 207.272798] [<ffffffff814a24ea>] mce_cpu_callback+0x15e/0x1ad
[ 207.272812] [<ffffffff814b6402>] notifier_call_chain+0x72/0x130
[ 207.272824] [<ffffffff81073d6e>] __raw_notifier_call_chain+0xe/0x10
[ 207.272839] [<ffffffff81498f76>] _cpu_down+0x1d6/0x350
[ 207.272851] [<ffffffff81499130>] cpu_down+0x40/0x60
[ 207.272862] [<ffffffff8149cc55>] store_online+0x75/0xe0
[ 207.272874] [<ffffffff813474a0>] dev_attr_store+0x20/0x30
[ 207.272886] [<ffffffff812090d9>] sysfs_write_file+0xd9/0x150
[ 207.272900] [<ffffffff8118e10b>] vfs_write+0xcb/0x130
[ 207.272911] [<ffffffff8118e924>] sys_write+0x64/0xa0
[ 207.272923] [<ffffffff814bb599>] system_call_fastpath+0x16/0x1b
[ 207.272936]
[ 207.272936] other info that might help us debug this:
[ 207.272936]
[ 207.272952] Chain exists of:
[ 207.272952] subsys mutex --> &mm->mmap_sem --> cpu_hotplug.lock
[ 207.272952]
[ 207.272973] Possible unsafe locking scenario:
[ 207.272973]
[ 207.272984] CPU0 CPU1
[ 207.272992] ---- ----
[ 207.273000] lock(cpu_hotplug.lock);
[ 207.273009] lock(&mm->mmap_sem);
[ 207.273020] lock(cpu_hotplug.lock);
[ 207.273031] lock(subsys mutex);
[ 207.273040]
[ 207.273040] *** DEADLOCK ***
[ 207.273040]
[ 207.273055] 5 locks held by bash/10493:
[ 207.273062] #0: (&buffer->mutex){+.+.+.}, at: [<ffffffff81209049>] sysfs_write_file+0x49/0x150
[ 207.273080] #1: (s_active#150){.+.+.+}, at: [<ffffffff812090c2>] sysfs_write_file+0xc2/0x150
[ 207.273099] #2: (x86_cpu_hotplug_driver_mutex){+.+.+.}, at: [<ffffffff81027557>] cpu_hotplug_driver_lock+0x17/0x20
[ 207.273121] #3: (cpu_add_remove_lock){+.+.+.}, at: [<ffffffff8149911c>] cpu_down+0x2c/0x60
[ 207.273140] #4: (cpu_hotplug.lock){+.+.+.}, at: [<ffffffff81046ccf>] cpu_hotplug_begin+0x2f/0x60
[ 207.273158]
[ 207.273158] stack backtrace:
[ 207.273170] Pid: 10493, comm: bash Not tainted 3.9.0-rc1-0.7-default+ #34
[ 207.273180] Call Trace:
[ 207.273192] [<ffffffff810ab373>] print_circular_bug+0x223/0x310
[ 207.273204] [<ffffffff810ae002>] __lock_acquire+0x13b2/0x15f0
[ 207.273216] [<ffffffff812086b0>] ? sysfs_hash_and_remove+0x60/0xc0
[ 207.273227] [<ffffffff810ae329>] lock_acquire+0xe9/0x120
[ 207.273239] [<ffffffff8134af27>] ? bus_remove_device+0x37/0x1c0
[ 207.273251] [<ffffffff814ad807>] mutex_lock_nested+0x37/0x360
[ 207.273263] [<ffffffff8134af27>] ? bus_remove_device+0x37/0x1c0
[ 207.273274] [<ffffffff812086b0>] ? sysfs_hash_and_remove+0x60/0xc0
[ 207.273286] [<ffffffff8134af27>] bus_remove_device+0x37/0x1c0
[ 207.273298] [<ffffffff81349114>] device_del+0x134/0x1f0
[ 207.273309] [<ffffffff813491f2>] device_unregister+0x22/0x60
[ 207.273321] [<ffffffff814a24ea>] mce_cpu_callback+0x15e/0x1ad
[ 207.273332] [<ffffffff814b6402>] notifier_call_chain+0x72/0x130
[ 207.273344] [<ffffffff81073d6e>] __raw_notifier_call_chain+0xe/0x10
[ 207.273356] [<ffffffff81498f76>] _cpu_down+0x1d6/0x350
[ 207.273368] [<ffffffff81027557>] ? cpu_hotplug_driver_lock+0x17/0x20
[ 207.273380] [<ffffffff81499130>] cpu_down+0x40/0x60
[ 207.273391] [<ffffffff8149cc55>] store_online+0x75/0xe0
[ 207.273402] [<ffffffff813474a0>] dev_attr_store+0x20/0x30
[ 207.273413] [<ffffffff812090d9>] sysfs_write_file+0xd9/0x150
[ 207.273425] [<ffffffff8118e10b>] vfs_write+0xcb/0x130
[ 207.273436] [<ffffffff8118e924>] sys_write+0x64/0xa0
[ 207.273447] [<ffffffff814bb599>] system_call_fastpath+0x16/0x1b
Which reports a false possitive deadlock because it sees:
1) load_module -> subsys_interface_register -> mc_deveice_add (*) -> subsys->p->mutex -> link_path_walk -> lookup_slow -> i_mutex
2) sys_write -> _cpu_down -> cpu_hotplug_begin -> cpu_hotplug.lock -> mce_cpu_callback -> mce_device_remove(**) -> device_unregister -> bus_remove_device -> subsys mutex
3) vfs_readdir -> i_mutex -> filldir64 -> might_fault -> might_lock_read(mmap_sem) -> page_fault -> mmap_sem -> drain_all_stock -> cpu_hotplug.lock
but
1) takes cpu_subsys subsys (*) but 2) takes mce_device subsys (**) so
the deadlock is not possible AFAICS.
The fix is quite simple. We can pull the key inside bus_type structure
because they are defined per device so the pointer will be unique as
well. bus_register doesn't need to be a macro anymore so change it
to the inline. We could get rid of __bus_register as there is no other
caller but maybe somebody will want to use a different key so keep it
around for now.
Reported-by: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
---
drivers/base/bus.c | 8 ++++----
include/linux/device.h | 12 +++---------
2 files changed, 7 insertions(+), 13 deletions(-)
diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 24eb078..4a299b3 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -898,18 +898,18 @@ static ssize_t bus_uevent_store(struct bus_type *bus,
static BUS_ATTR(uevent, S_IWUSR, NULL, bus_uevent_store);
/**
- * __bus_register - register a driver-core subsystem
+ * bus_register - register a driver-core subsystem
* @bus: bus to register
- * @key: lockdep class key
*
* Once we have that, we register the bus with the kobject
* infrastructure, then register the children subsystems it has:
* the devices and drivers that belong to the subsystem.
*/
-int __bus_register(struct bus_type *bus, struct lock_class_key *key)
+int bus_register(struct bus_type *bus)
{
int retval;
struct subsys_private *priv;
+ struct lock_class_key *key = &bus->lock_key;
priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);
if (!priv)
@@ -981,7 +981,7 @@ out:
bus->p = NULL;
return retval;
}
-EXPORT_SYMBOL_GPL(__bus_register);
+EXPORT_SYMBOL_GPL(bus_register);
/**
* bus_unregister - remove a bus from the system
diff --git a/include/linux/device.h b/include/linux/device.h
index 43dcda9..6793a19 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -110,17 +110,11 @@ struct bus_type {
struct iommu_ops *iommu_ops;
struct subsys_private *p;
+ struct lock_class_key lock_key;
};
-/* This is a #define to keep the compiler from merging different
- * instances of the __key variable */
-#define bus_register(subsys) \
-({ \
- static struct lock_class_key __key; \
- __bus_register(subsys, &__key); \
-})
-extern int __must_check __bus_register(struct bus_type *bus,
- struct lock_class_key *key);
+extern int __must_check bus_register(struct bus_type *bus);
+
extern void bus_unregister(struct bus_type *bus);
extern int __must_check bus_rescan_devices(struct bus_type *bus);
--
1.7.10.4
--
Michal Hocko
SUSE Labs
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