pci-sysfs: replace mutex_lock with mutex_trylock to avoid potential deadlock situation
PATCH RESEND 1/1 pci-sysfs: replace mutex_lock with mutex_trylock to avoid potential deadlock situation
There is a potential deadlock situation when we manipulate the pci-sysfs user interfaces from different bus hierarchy simultaneously, described as following:
path1: sysfs remove device: | path2: sysfs rescan device:
sysfs_schedule_callback_work() | sysfs_write_file()
remove_callback() | flush_write_buffer()
*1* mutex_lock(&pci_remove_rescan_mutex)|*2* sysfs_get_active(attr_sd)
... | dev_attr_store()
device_remove_file() | dev_rescan_store()
... |*4* mutex_lock(&pci_remove_rescan_mutex)
*3* sysfs_deactivate(sd) | ...
wait_for_completion() |*5* sysfs_put_active(attr_sd)*6* mutex_unlock(&pci_remove_rescan_mutex)
If path1 firstly holds the pci_remove_rescan_mutex at *1*, then another path called path2 actived and runs to *2* before path1 runs to *3*, we now runs to a deadlock situation:
Path1 holds the mutex waiting path2 to decrease sysfs_dirent's s_active counter at *5*, but path2 is blocked at *4* when trying to get the pci_remove_rescan_mutex. The mutex won't be put by path1 until it reach *6*, but it's now blocked at *3*.
The circumvent approach is if we find someone else is manipulating the pci-tree we simply abort current operation to avoid deadlock.
*dmesg ifno*:
(snip)
1000e 0000:1c:00.0: eth9: Intel(R) PRO/1000 Network Connection
sd 13:2:0:0: [sdb] Attached SCSI disk
e1000e 0000:1c:00.0: eth9: MAC: 0, PHY: 4, PBA No: D50228-005
e1000e 0000:1c:00.1: Disabling ASPM L1
e1000e 0000:1c:00.1: Interrupt Throttling Rate (ints/sec) set to dynamic conservative mode e1000e 0000:1c:00.1: irq 143 for MSI/MSI-X
e1000e 0000:1c:00.1: eth10: (PCI Express:2.5GT/s:Width x4) 00:15:17:cd:96:bf e1000e 0000:1c:00.1: eth10: Intel(R) PRO/1000 Network Connection
e1000e 0000:1c:00.1: eth10: MAC: 0, PHY: 4, PBA No: D50228-005
INFO: task bash:62982 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
bash D 0000000000000000 0 62982 62978 0x00000080
ffff88038b277db8 0000000000000082 ffff88038b277fd8 0000000000013940 ffff88038b276010 0000000000013940 0000000000013940 0000000000013940 ffff88038b277fd8 0000000000013940 ffff880377449e30 ffff8806e822c670
Call Trace: [<ffffffff8151ba79>] schedule+0x29/0x70 [<ffffffff8151bd6e>] schedule_preempt_disabled+0xe/0x10 [<ffffffff8151a4e3>] __mutex_lock_slowpath+0xd3/0x150 [<ffffffff8151a3eb>] mutex_lock+0x2b/0x50 [<ffffffff812821dc>] dev_rescan_store+0x5c/0x80 [<ffffffff81341800>] dev_attr_store+0x20/0x30 [<ffffffff811e3eef>] sysfs_write_file+0xef/0x170 [<ffffffff81173d08>] vfs_write+0xc8/0x190 [<ffffffff81173ed1>] sys_write+0x51/0x90 [<ffffffff81524b29>] system_call_fastpath+0x16/0x1b INFO: task bash:64141 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
bash D ffffffff81610460 0 64141 64136 0x00000080
ffff8803540e9db8 0000000000000086 ffff8803540e9fd8 0000000000013940 ffff8803540e8010 0000000000013940 0000000000013940 0000000000013940 ffff8803540e9fd8 0000000000013940 ffff8807db338a10 ffff8806f09abc60
Call Trace: [<ffffffff8151ba79>] schedule+0x29/0x70 [<ffffffff8151bd6e>] schedule_preempt_disabled+0xe/0x10 [<ffffffff8151a4e3>] __mutex_lock_slowpath+0xd3/0x150 [<ffffffff8151a3eb>] mutex_lock+0x2b/0x50 [<ffffffff812821dc>] dev_rescan_store+0x5c/0x80 [<ffffffff81341800>] dev_attr_store+0x20/0x30 [<ffffffff811e3eef>] sysfs_write_file+0xef/0x170 [<ffffffff81173d08>] vfs_write+0xc8/0x190 [<ffffffff81173ed1>] sys_write+0x51/0x90 [<ffffffff81524b29>] system_call_fastpath+0x16/0x1b INFO: task kworker/u:3:64451 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u:3 D ffffffff81610460 0 64451 2 0x00000080
ffff8807d51b7a30 0000000000000046 ffff8807d51b7fd8 0000000000013940 ffff8807d51b6010 0000000000013940 0000000000013940 0000000000013940 ffff8807d51b7fd8 0000000000013940 ffff8807db339420 ffff88037744b250
Call Trace: [<ffffffff8151ba79>] schedule+0x29/0x70 [<ffffffff81519ded>] schedule_timeout+0x19d/0x220 [<ffffffff81165f92>] ? __slab_free+0x1f2/0x2f0 [<ffffffff8151b8fe>] wait_for_common+0x11e/0x190 [<ffffffff8108a6e0>] ? try_to_wake_up+0x2c0/0x2c0 [<ffffffff8151ba4d>] wait_for_completion+0x1d/0x20 [<ffffffff811e53e8>] sysfs_addrm_finish+0xb8/0xd0 [<ffffffff811e4320>] ? sysfs_schedule_callback+0x1e0/0x1e0 [<ffffffff811e33f0>] sysfs_hash_and_remove+0x60/0xb0 [<ffffffff811e43c9>] sysfs_remove_file+0x39/0x50 [<ffffffff81342cb7>] device_remove_file+0x17/0x20 [<ffffffff8134505c>] bus_remove_device+0xdc/0x180 [<ffffffff81342eb0>] device_del+0x120/0x1d0 [<ffffffff81342f82>] device_unregister+0x22/0x60 [<ffffffff8127ade4>] pci_stop_bus_device+0x94/0xa0 [<ffffffff8127ad90>] pci_stop_bus_device+0x40/0xa0 [<ffffffff8127ad90>] pci_stop_bus_device+0x40/0xa0 [<ffffffff8127ad90>] pci_stop_bus_device+0x40/0xa0 [<ffffffff8127af66>] pci_stop_and_remove_bus_device+0x16/0x30 [<ffffffff81282359>] remove_callback+0x29/0x40 [<ffffffff811e4344>] sysfs_schedule_callback_work+0x24/0x70 [<ffffffff81070009>] process_one_work+0x179/0x4b0 [<ffffffff8107210e>] worker_thread+0x12e/0x330 [<ffffffff81071fe0>] ? manage_workers+0x110/0x110 [<ffffffff8107705e>] kthread+0x9e/0xb0 [<ffffffff81525bc4>] kernel_thread_helper+0x4/0x10 [<ffffffff81076fc0>] ? kthread_freezable_should_stop+0x70/0x70 [<ffffffff81525bc0>] ? gs_change+0x13/0x13
--- drivers/pci/pci-sysfs.c | 42 ++++++++++++++++++++++++++---------------- 1 files changed, 26 insertions(+), 16 deletions(-)
drivers/pci/pci-sysfs.c +26 -16
@@ -295,10 +295,13 @@ static ssize_t bus_rescan_store(struct bus_type *bus, const char *buf,return -EINVAL ;if (val) { -mutex_lock (&pci_remove_rescan_mutex); -while ((b =pci_find_next_bus (b)) !=NULL ) -pci_rescan_bus (b); -mutex_unlock (&pci_remove_rescan_mutex); +if (mutex_trylock (&pci_remove_rescan_mutex)) { +while ((b =pci_find_next_bus (b)) !=NULL ) +pci_rescan_bus (b); +mutex_unlock (&pci_remove_rescan_mutex); + }else { +return 0 ; + } }return count; }
@@ -319,9 +322,12 @@ dev_rescan_store(struct device *dev, struct device_attribute *attr,return -EINVAL ;if (val) { -mutex_lock (&pci_remove_rescan_mutex); -pci_rescan_bus (pdev->bus); -mutex_unlock (&pci_remove_rescan_mutex); +if (mutex_trylock (&pci_remove_rescan_mutex)) { +pci_rescan_bus (pdev->bus); +mutex_unlock (&pci_remove_rescan_mutex); + }else { +return 0 ; + } }return count; }
@@ -330,9 +336,10 @@ static void remove_callback(struct device *dev) {struct pci_dev *pdev =to_pci_dev (dev); -mutex_lock (&pci_remove_rescan_mutex); -pci_stop_and_remove_bus_device (pdev); -mutex_unlock (&pci_remove_rescan_mutex); +if (mutex_trylock (&pci_remove_rescan_mutex)) { +pci_stop_and_remove_bus_device (pdev); +mutex_unlock (&pci_remove_rescan_mutex); + } } static ssize_t
@@ -366,12 +373,15 @@ dev_bus_rescan_store(struct device *dev, struct device_attribute *attr,return -EINVAL ;if (val) { -mutex_lock (&pci_remove_rescan_mutex); -if (!pci_is_root_bus (bus) &&list_empty (&bus->devices)) -pci_rescan_bus_bridge_resize (bus->self); -else -pci_rescan_bus (bus); -mutex_unlock (&pci_remove_rescan_mutex); +if (mutex_trylock (&pci_remove_rescan_mutex)) { +if (!pci_is_root_bus (bus) &&list_empty (&bus->devices)) +pci_rescan_bus_bridge_resize (bus->self); +else +pci_rescan_bus (bus); +mutex_unlock (&pci_remove_rescan_mutex); + }else { +return 0 ; + } }return count; }
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1.7.1