A deadlock triggered by a NONFATAL AER event during a sysfs "sriov_numvfs"
operation:
enable one VF
# echo 1 > /sys/devices/pci0000:74/0000:74:00.0/0000:75:00.0/sriov_numvfs
The sysfs "sriov_numvfs" side is:
sriov_numvfs_store
device_lock # hold the device_lock
...
pci_enable_sriov
sriov_enable
...
pci_device_add
down_write(&pci_bus_sem) # wait for the pci_bus_sem
The AER side is:
pcie_do_recovery
pci_walk_bus
down_read(&pci_bus_sem) # hold the pci_bus_sem
report_resume
device_lock # wait for device_unlock()
The calltrace is as below:
[ 258.411464] INFO: task kworker/0:1:13 blocked for more than 120 seconds.
[ 258.418139] Tainted: G C O 5.1.0-rc1-ge2e3ca0 #1
[ 258.424379] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 258.432172] kworker/0:1 D 0 13 2 0x00000028
[ 258.437640] Workqueue: events aer_recover_work_func
[ 258.442496] Call trace:
[ 258.444933] __switch_to+0xb4/0x1b8
[ 258.448409] __schedule+0x1ec/0x720
[ 258.451884] schedule+0x38/0x90
[ 258.455012] schedule_preempt_disabled+0x20/0x38
[ 258.459610] __mutex_lock.isra.1+0x150/0x518
[ 258.463861] __mutex_lock_slowpath+0x10/0x18
[ 258.468112] mutex_lock+0x34/0x40
[ 258.471413] report_resume+0x1c/0x78
[ 258.474973] pci_walk_bus+0x58/0xb0
[ 258.478451] pcie_do_recovery+0x18c/0x248
[ 258.482445] aer_recover_work_func+0xe0/0x118
[ 258.486783] process_one_work+0x1e4/0x468
[ 258.490776] worker_thread+0x40/0x450
[ 258.494424] kthread+0x128/0x130
[ 258.497639] ret_from_fork+0x10/0x1c
[ 258.501329] INFO: task flr.sh:4534 blocked for more than 120 seconds.
[ 258.507742] Tainted: G C O 5.1.0-rc1-ge2e3ca0 #1
[ 258.513980] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 258.521774] flr.sh D 0 4534 4504 0x00000000
[ 258.527235] Call trace:
[ 258.529671] __switch_to+0xb4/0x1b8
[ 258.533146] __schedule+0x1ec/0x720
[ 258.536619] schedule+0x38/0x90
[ 258.539749] rwsem_down_write_failed+0x14c/0x210
[ 258.544347] down_write+0x48/0x60
[ 258.547648] pci_device_add+0x1a0/0x290
[ 258.551469] pci_iov_add_virtfn+0x190/0x358
[ 258.555633] sriov_enable+0x24c/0x480
[ 258.559279] pci_enable_sriov+0x14/0x28
[ 258.563101] hisi_zip_sriov_configure+0x64/0x100 [hisi_zip]
[ 258.568649] sriov_numvfs_store+0xc4/0x190
[ 258.572728] dev_attr_store+0x18/0x28
[ 258.576375] sysfs_kf_write+0x3c/0x50
[ 258.580024] kernfs_fop_write+0x114/0x1d8
[ 258.584018] __vfs_write+0x18/0x38
[ 258.587404] vfs_write+0xa4/0x1b0
[ 258.590705] ksys_write+0x60/0xd8
[ 258.594007] __arm64_sys_write+0x18/0x20
[ 258.597914] el0_svc_common+0x5c/0x100
[ 258.601646] el0_svc_handler+0x2c/0x80
[ 258.605381] el0_svc+0x8/0xc
[ 379.243461] INFO: task kworker/0:1:13 blocked for more than 241 seconds.
[ 379.250134] Tainted: G C O 5.1.0-rc1-ge2e3ca0 #1
[ 379.256373] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Using the same locking order is a good way to solve this AB->BA kind of
deadlock. Adjust the locking order of the AER side, taking device_lock
firstly and then the pci_bus_sem, to make sure it's locking order is the
same as the sriov side. This patch solves the above deadlock issue only
with little changes.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=203981
Signed-off-by: Jay Fang <f.fangjian@xxxxxxxxxx>
---
drivers/pci/pcie/err.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index 773197a..dcc8638 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -50,7 +50,6 @@ static int report_error_detected(struct pci_dev *dev,
pci_ers_result_t vote;
const struct pci_error_handlers *err_handler;
- device_lock(&dev->dev);
if (!pci_dev_set_io_state(dev, state) ||
!dev->driver ||
!dev->driver->err_handler ||
@@ -71,7 +70,6 @@ static int report_error_detected(struct pci_dev *dev,
}
pci_uevent_ers(dev, vote);
*result = merge_result(*result, vote);
- device_unlock(&dev->dev);
return 0;
}
@@ -90,7 +88,6 @@ static int report_mmio_enabled(struct pci_dev *dev, void *data)
pci_ers_result_t vote, *result = data;
const struct pci_error_handlers *err_handler;
- device_lock(&dev->dev);
if (!dev->driver ||
!dev->driver->err_handler ||
!dev->driver->err_handler->mmio_enabled)
@@ -100,7 +97,6 @@ static int report_mmio_enabled(struct pci_dev *dev, void *data)
vote = err_handler->mmio_enabled(dev);
*result = merge_result(*result, vote);
out:
- device_unlock(&dev->dev);
return 0;
}
@@ -109,7 +105,6 @@ static int report_slot_reset(struct pci_dev *dev, void *data)
pci_ers_result_t vote, *result = data;
const struct pci_error_handlers *err_handler;
- device_lock(&dev->dev);
if (!dev->driver ||
!dev->driver->err_handler ||
!dev->driver->err_handler->slot_reset)
@@ -119,7 +114,6 @@ static int report_slot_reset(struct pci_dev *dev, void *data)
vote = err_handler->slot_reset(dev);
*result = merge_result(*result, vote);
out:
- device_unlock(&dev->dev);
return 0;
}
@@ -127,7 +121,6 @@ static int report_resume(struct pci_dev *dev, void *data)
{
const struct pci_error_handlers *err_handler;
- device_lock(&dev->dev);
if (!pci_dev_set_io_state(dev, pci_channel_io_normal) ||
!dev->driver ||
!dev->driver->err_handler ||
@@ -138,7 +131,6 @@ static int report_resume(struct pci_dev *dev, void *data)
err_handler->resume(dev);
out:
pci_uevent_ers(dev, PCI_ERS_RESULT_RECOVERED);
- device_unlock(&dev->dev);
return 0;
}
@@ -198,6 +190,8 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
dev = dev->bus->self;
bus = dev->subordinate;
+ device_lock(&dev->dev);
+
pci_dbg(dev, "broadcast error_detected message\n");
if (state == pci_channel_io_frozen)
pci_walk_bus(bus, report_frozen_detected, &status);
@@ -231,12 +225,14 @@ void pcie_do_recovery(struct pci_dev *dev, enum pci_channel_state state,
pci_dbg(dev, "broadcast resume message\n");
pci_walk_bus(bus, report_resume, &status);
+ device_unlock(&dev->dev);
pci_aer_clear_device_status(dev);
pci_cleanup_aer_uncorrect_error_status(dev);
pci_info(dev, "AER: Device recovery successful\n");
return;
failed:
+ device_unlock(&dev->dev);
pci_uevent_ers(dev, PCI_ERS_RESULT_DISCONNECT);
/* TODO: Should kernel panic here? */
--
2.8.1
