In pci_dev_lock(), we hold pci_lock for configuration access first,
then is device_lock. But in sriov enable routine, we hold device_lock
first and pci_lock subsequently. The inconsistent lock order will have
potential deadlock problem.
In pci_dev_lock():
pci_dev_lock()
pci_cfg_access_lock()
device_lock()
When adding VF by sysfs:
sriov_numvfs_store()
device_lock()
...
sriov_enable()
pci_cfg_access_lock()
Adjust the lock order in pci_dev_lock(), pci_dev_trylock() and
pci_dev_unlock() to avoid potential deadlock condition.
Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
---
I split this patch from the series sent in Jan as I reproduced the deadlock
contidion, by enable VFs of the function while perform flr through sysfs
interface.
The calltrace is like:
NFO: task kworker/0:2:404 blocked for more than 120 seconds.
[ 3517.118941] INFO: task kworker/0:2:404 blocked for more than 120 seconds.
[ 3517.125703] Tainted: G O 5.5.0-rc4-gda2956a #1
[ 3517.131946] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3517.139745] kworker/0:2 D 0 404 2 0x00000028
[ 3517.145216] Workqueue: events work_for_cpu_fn
[ 3517.149558] Call trace:
[ 3517.152004] __switch_to+0xb4/0x200
[ 3517.155484] __schedule+0x2e4/0x620
[ 3517.158963] schedule+0x80/0x120
[ 3517.162178] pci_wait_cfg+0x8c/0xd8
[ 3517.165654] pci_cfg_access_lock+0x34/0x58
[ 3517.169736] sriov_enable+0x1e4/0x430
[ 3517.173386] pci_enable_sriov+0x30/0x48
[ 3517.177215] hisi_qm_sriov_enable+0x60/0xf0 [hisi_qm]
[ 3517.182251] sec_probe+0x278/0x5f8 [hisi_sec2]
[ 3517.186680] local_pci_probe+0x44/0x98
[ 3517.190416] work_for_cpu_fn+0x20/0x30
[ 3517.194153] process_one_work+0x158/0x4b8
[ 3517.198149] worker_thread+0x21c/0x498
[ 3517.201885] kthread+0xfc/0x128
[ 3517.205016] ret_from_fork+0x10/0x1c
[ 3517.208708] INFO: task bash:7025 blocked for more than 120 seconds.
[ 3517.214951] Tainted: G O 5.5.0-rc4-gda2956a #1
[ 3517.221192] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3517.228989] bash D 0 7025 5082 0x00000200
[ 3517.234455] Call trace:
[ 3517.236897] __switch_to+0xb4/0x200
[ 3517.240373] __schedule+0x2e4/0x620
[ 3517.243850] schedule+0x80/0x120
[ 3517.247068] schedule_preempt_disabled+0x28/0x40
[ 3517.251668] __mutex_lock.isra.9+0x24c/0x560
[ 3517.255927] __mutex_lock_slowpath+0x24/0x30
[ 3517.260182] mutex_lock+0x5c/0x68
[ 3517.263487] pci_reset_function+0x38/0x80
[ 3517.267483] reset_store+0x70/0xc0
[ 3517.270870] dev_attr_store+0x44/0x60
[ 3517.274521] sysfs_kf_write+0x5c/0x78
[ 3517.278171] kernfs_fop_write+0x104/0x210
[ 3517.282168] __vfs_write+0x48/0x90
[ 3517.285560] vfs_write+0xbc/0x1c8
[ 3517.288864] ksys_write+0x74/0x100
[ 3517.292256] __arm64_sys_write+0x24/0x30
[ 3517.296167] el0_svc_common.constprop.3+0x110/0x200
[ 3517.301029] el0_svc_handler+0x34/0xa0
[ 3517.304765] el0_svc+0x14/0x40
[ 3517.307810] el0_sync_handler+0xb0/0x28c
[ 3517.311720] el0_sync+0x140/0x180
drivers/pci/pci.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d828ca8..4abfbad 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4880,18 +4880,19 @@ static int pci_dev_reset_slot_function(struct pci_dev *dev, int probe)
static void pci_dev_lock(struct pci_dev *dev)
{
- pci_cfg_access_lock(dev);
/* block PM suspend, driver probe, etc. */
device_lock(&dev->dev);
+
+ pci_cfg_access_lock(dev);
}
/* Return 1 on successful lock, 0 on contention */
static int pci_dev_trylock(struct pci_dev *dev)
{
- if (pci_cfg_access_trylock(dev)) {
- if (device_trylock(&dev->dev))
+ if (device_trylock(&dev->dev)) {
+ if (pci_cfg_access_trylock(dev))
return 1;
- pci_cfg_access_unlock(dev);
+ device_unlock(&dev->dev);
}
return 0;
@@ -4899,8 +4900,8 @@ static int pci_dev_trylock(struct pci_dev *dev)
static void pci_dev_unlock(struct pci_dev *dev)
{
- device_unlock(&dev->dev);
pci_cfg_access_unlock(dev);
+ device_unlock(&dev->dev);
}
static void pci_dev_save_and_disable(struct pci_dev *dev)
--
2.8.1
