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Subject[PATCH 3/4] pci aer: fix deadlock in do_recovery
Date
CPU0					CPU1
---------------------------------------------------------------------
__driver_attach()
device_lock(&dev->mutex) <--- device mutex lock here
driver_probe_device()
pci_enable_sriov()
pci_iov_add_virtfn()
pci_device_add()
aer_isr() <--- pci aer error
do_recovery()
broadcast_error_message()
pci_walk_bus()
down_read(&pci_bus_sem) <--- rd sem
down_write(&pci_bus_sem) <-- stuck on wr sem
report_error_detected()
device_lock(&dev->mutex)<--- DEAD LOCK

This can also happen when aer error occurs while pci_dev->sriov_config() is
called.

Only fix I could think of is to lock &pci_bus_sem and try locking all
device->mutex under that pci_bus. If it fails, unlock all device->mutex
and &pci_bus_sem and try again.

[ 70.984091] pcieport 0000:00:02.0: AER: Uncorrected (Non-Fatal) error received: id=0010
[ 70.984112] pcieport 0000:00:02.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, id=0010(Requester ID)
[ 70.984116] pcieport 0000:00:02.0: device [8086:3c04] error status/mask=00004000/00100000
[ 70.984120] pcieport 0000:00:02.0: [14] Completion Timeout (First)
...
[ 107.484190] INFO: task kworker/0:1:76 blocked for more than 30 seconds.
[ 107.563619] Not tainted 4.13.0+ #28
[ 107.611618] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 107.705368] kworker/0:1 D 0 76 2 0x80000000
[ 107.771050] Workqueue: events aer_isr
[ 107.814895] Call Trace:
[ 107.844181] __schedule+0x312/0xa40
[ 107.885928] schedule+0x3d/0x90
[ 107.923506] schedule_preempt_disabled+0x15/0x20
[ 107.978773] __mutex_lock+0x304/0xa30
[ 108.022594] ? dev_printk_emit+0x3b/0x50
[ 108.069534] ? report_error_detected+0xa6/0x210
[ 108.123770] mutex_lock_nested+0x1b/0x20
[ 108.170713] ? mutex_lock_nested+0x1b/0x20
[ 108.219730] report_error_detected+0xa6/0x210
[ 108.271881] ? aer_recover_queue+0xe0/0xe0
[ 108.320904] pci_walk_bus+0x46/0x90
[ 108.362645] ? aer_recover_queue+0xe0/0xe0
[ 108.411658] broadcast_error_message+0xc3/0xf0
[ 108.464835] do_recovery+0x34/0x220
[ 108.506569] ? get_device_error_info+0x92/0x130
[ 108.560785] aer_isr+0x28f/0x3b0
[ 108.599410] process_one_work+0x277/0x6c0
[ 108.647399] worker_thread+0x4d/0x3b0
[ 108.691218] kthread+0x171/0x190
[ 108.729830] ? process_one_work+0x6c0/0x6c0
[ 108.779888] ? kthread_create_on_node+0x40/0x40
[ 108.834110] ret_from_fork+0x2a/0x40
[ 108.876916] INFO: task kworker/0:2:205 blocked for more than 30 seconds.
[ 108.957129] Not tainted 4.13.0+ #28
[ 109.005114] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 109.098873] kworker/0:2 D 0 205 2 0x80000000
[ 109.164544] Workqueue: events work_for_cpu_fn
[ 109.216681] Call Trace:
[ 109.245943] __schedule+0x312/0xa40
[ 109.287687] ? rwsem_down_write_failed+0x308/0x4f0
[ 109.345021] schedule+0x3d/0x90
[ 109.382603] rwsem_down_write_failed+0x30d/0x4f0
[ 109.437869] ? __lock_acquire+0x75c/0x1410
[ 109.486910] call_rwsem_down_write_failed+0x17/0x30
[ 109.545287] ? call_rwsem_down_write_failed+0x17/0x30
[ 109.605752] down_write+0x88/0xb0
[ 109.645410] pci_device_add+0x158/0x240
[ 109.691313] pci_iov_add_virtfn+0x24f/0x340
[ 109.741375] pci_enable_sriov+0x32b/0x420
[ 109.789466] ? pci_read+0x2c/0x30
[ 109.829142] enic_probe+0x5d4/0xff0 [enic]
[ 109.878184] ? trace_hardirqs_on+0xd/0x10
[ 109.926180] local_pci_probe+0x42/0xa0
[ 109.971037] work_for_cpu_fn+0x14/0x20
[ 110.015898] process_one_work+0x277/0x6c0
[ 110.063884] worker_thread+0x1d6/0x3b0
[ 110.108750] kthread+0x171/0x190
[ 110.147363] ? process_one_work+0x6c0/0x6c0
[ 110.197426] ? kthread_create_on_node+0x40/0x40
[ 110.251642] ret_from_fork+0x2a/0x40
[ 110.294448] INFO: task systemd-udevd:492 blocked for more than 30 seconds.
[ 110.376742] Not tainted 4.13.0+ #28
[ 110.424715] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 110.518457] systemd-udevd D 0 492 444 0x80000180
[ 110.584116] Call Trace:
[ 110.613382] __schedule+0x312/0xa40
[ 110.655127] ? wait_for_completion+0x14a/0x1d0
[ 110.708302] schedule+0x3d/0x90
[ 110.745875] schedule_timeout+0x26e/0x5b0
[ 110.793887] ? wait_for_completion+0x14a/0x1d0
[ 110.847068] wait_for_completion+0x169/0x1d0
[ 110.898165] ? wait_for_completion+0x169/0x1d0
[ 110.951354] ? wake_up_q+0x80/0x80
[ 110.992060] flush_work+0x237/0x300
[ 111.033795] ? flush_workqueue_prep_pwqs+0x1b0/0x1b0
[ 111.093224] ? wait_for_completion+0x5a/0x1d0
[ 111.145363] ? flush_work+0x237/0x300
[ 111.189189] work_on_cpu+0x94/0xb0
[ 111.229894] ? work_is_static_object+0x20/0x20
[ 111.283070] ? pci_device_shutdown+0x60/0x60
[ 111.334173] pci_device_probe+0x17a/0x190
[ 111.382163] driver_probe_device+0x2ff/0x450
[ 111.433260] __driver_attach+0x103/0x140
[ 111.480195] ? driver_probe_device+0x450/0x450
[ 111.533381] bus_for_each_dev+0x74/0xb0
[ 111.579276] driver_attach+0x1e/0x20
[ 111.622056] bus_add_driver+0x1ca/0x270
[ 111.667955] ? 0xffffffffc039c000
[ 111.707616] driver_register+0x60/0xe0
[ 111.752472] ? 0xffffffffc039c000
[ 111.792126] __pci_register_driver+0x6b/0x70
[ 111.843275] enic_init_module+0x38/0x1000 [enic]
[ 111.898533] do_one_initcall+0x50/0x192
[ 111.944428] ? trace_hardirqs_on+0xd/0x10
[ 111.992408] do_init_module+0x5f/0x1f2
[ 112.037274] load_module+0x1740/0x1f70
[ 112.082148] SYSC_finit_module+0xd7/0xf0
[ 112.129083] ? SYSC_finit_module+0xd7/0xf0
[ 112.178106] SyS_finit_module+0xe/0x10
[ 112.222972] do_syscall_64+0x69/0x180
[ 112.266793] entry_SYSCALL64_slow_path+0x25/0x25
[ 112.322047] RIP: 0033:0x7f3da098b559
[ 112.364826] RSP: 002b:00007ffeb3306a38 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[ 112.455447] RAX: ffffffffffffffda RBX: 0000557fe41ed3d0 RCX: 00007f3da098b559
[ 112.540860] RDX: 0000000000000000 RSI: 00007f3da14c79c5 RDI: 0000000000000006
[ 112.626281] RBP: 00007f3da14c79c5 R08: 0000000000000000 R09: 00007ffeb3306b50
[ 112.711698] R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000000
[ 112.797114] R13: 0000557fe420e210 R14: 0000000000020000 R15: 0000557fe2c1ef4a
[ 112.882568]
Showing all locks held in the system:
[ 112.956545] 5 locks held by kworker/0:1/76:
[ 113.006616] #0: ("events"){+.+.}, at: [<ffffffffb00b10ed>] process_one_work+0x1ed/0x6c0
[ 113.104535] #1: ((&rpc->dpc_handler)){+.+.}, at: [<ffffffffb00b10ed>] process_one_work+0x1ed/0x6c0
[ 113.213894] #2: (&rpc->rpc_mutex){+.+.}, at: [<ffffffffb0505ca2>] aer_isr+0x32/0x3b0
[ 113.308711] #3: (pci_bus_sem){++++}, at: [<ffffffffb04ea18a>] pci_walk_bus+0x2a/0x90
[ 113.403501] #4: (&dev->mutex){....}, at: [<ffffffffb0505706>] report_error_detected+0xa6/0x210
[ 113.508715] 3 locks held by kworker/0:2/205:
[ 113.559808] #0: ("events"){+.+.}, at: [<ffffffffb00b10ed>] process_one_work+0x1ed/0x6c0
[ 113.657718] #1: ((&wfc.work)){+.+.}, at: [<ffffffffb00b10ed>] process_one_work+0x1ed/0x6c0
[ 113.758745] #2: (pci_bus_sem){++++}, at: [<ffffffffb04ec978>] pci_device_add+0x158/0x240
[ 113.857710] 1 lock held by khungtaskd/239:
[ 113.906729] #0: (tasklist_lock){.+.+}, at: [<ffffffffb00f07dd>] debug_show_all_locks+0x3d/0x1a0
[ 114.012972] 2 locks held by systemd-udevd/492:
[ 114.066148] #0: (&dev->mutex){....}, at: [<ffffffffb06254d5>] __driver_attach+0x55/0x140
[ 114.165107] #1: (&dev->mutex){....}, at: [<ffffffffb06254f2>] __driver_attach+0x72/0x140

[ 114.281879] =============================================

Signed-off-by: Govindarajulu Varadarajan <gvaradar@cisco.com>
---
drivers/pci/pcie/aer/aerdrv_core.c | 50 ++++++++++++++++++++++++++++++--------
1 file changed, 40 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
index 890efcc574cb..a3869a3b6e82 100644
--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/drivers/pci/pcie/aer/aerdrv_core.c
@@ -26,6 +26,7 @@
#include <linux/slab.h>
#include <linux/kfifo.h>
#include "aerdrv.h"
+#include "../../pci.h"

#define PCI_EXP_AER_FLAGS (PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | \
PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE)
@@ -241,7 +242,6 @@ static int report_error_detected(struct pci_dev *dev, void *data)
struct aer_broadcast_data *result_data;
result_data = (struct aer_broadcast_data *) data;

- device_lock(&dev->dev);
dev->error_state = result_data->state;

if (!dev->driver ||
@@ -281,7 +281,6 @@ static int report_error_detected(struct pci_dev *dev, void *data)
}

result_data->result = merge_result(result_data->result, vote);
- device_unlock(&dev->dev);
return 0;
}

@@ -292,7 +291,6 @@ static int report_mmio_enabled(struct pci_dev *dev, void *data)
struct aer_broadcast_data *result_data;
result_data = (struct aer_broadcast_data *) data;

- device_lock(&dev->dev);
if (!dev->driver ||
!dev->driver->err_handler ||
!dev->driver->err_handler->mmio_enabled)
@@ -302,7 +300,6 @@ static int report_mmio_enabled(struct pci_dev *dev, void *data)
vote = err_handler->mmio_enabled(dev);
result_data->result = merge_result(result_data->result, vote);
out:
- device_unlock(&dev->dev);
return 0;
}

@@ -313,7 +310,6 @@ static int report_slot_reset(struct pci_dev *dev, void *data)
struct aer_broadcast_data *result_data;
result_data = (struct aer_broadcast_data *) data;

- device_lock(&dev->dev);
if (!dev->driver ||
!dev->driver->err_handler ||
!dev->driver->err_handler->slot_reset)
@@ -323,7 +319,6 @@ static int report_slot_reset(struct pci_dev *dev, void *data)
vote = err_handler->slot_reset(dev);
result_data->result = merge_result(result_data->result, vote);
out:
- device_unlock(&dev->dev);
return 0;
}

@@ -331,7 +326,6 @@ static int report_resume(struct pci_dev *dev, void *data)
{
const struct pci_error_handlers *err_handler;

- device_lock(&dev->dev);
dev->error_state = pci_channel_io_normal;

if (!dev->driver ||
@@ -342,10 +336,46 @@ static int report_resume(struct pci_dev *dev, void *data)
err_handler = dev->driver->err_handler;
err_handler->resume(dev);
out:
- device_unlock(&dev->dev);
return 0;
}

+static void aer_pci_walk_bus(struct pci_bus *bus,
+ int (*cb)(struct pci_dev *, void *),
+ struct aer_broadcast_data *res)
+{
+ bool locked;
+ uint8_t i;
+
+ for (i = 1; i; i++) {
+ /* PCI driver could hold device->mutex lock and call driver
+ * cb functions which may try to aquire pci_bus_sem.
+ * Trying to aquiring device->mutex lock holding pci_bus_sem
+ * could lead to deadlock.
+ *
+ * Holding pci_bus_sem lets try to aquire device->mutex lock.
+ * If trylock(device->mutex) fails, unlock pci_bus_sem and
+ * try again.
+ */
+ down_read(&pci_bus_sem);
+ locked = __pci_bus_trylock(bus, pci_device_trylock,
+ pci_device_unlock);
+ if (locked)
+ goto out;
+ up_read(&pci_bus_sem);
+ dev_info(&bus->self->dev, "Could not aquire device lock on all subordinates, trying again.");
+ msleep(25);
+ };
+
+ res->result = PCI_ERS_RESULT_NONE;
+ dev_err(&bus->self->dev, "Could not aquire lock. No aer recovery done.");
+ return;
+out:
+ /* all devices under this subordinate is locked */
+ __pci_walk_bus(bus, cb, res);
+ __pci_bus_unlock(bus, pci_device_unlock);
+ up_read(&pci_bus_sem);
+}
+
/**
* broadcast_error_message - handle message broadcast to downstream drivers
* @dev: pointer to from where in a hierarchy message is broadcasted down
@@ -380,7 +410,7 @@ static pci_ers_result_t broadcast_error_message(struct pci_dev *dev,
*/
if (cb == report_error_detected)
dev->error_state = state;
- pci_walk_bus(dev->subordinate, cb, &result_data);
+ aer_pci_walk_bus(dev->subordinate, cb, &result_data);
if (cb == report_resume) {
pci_cleanup_aer_uncorrect_error_status(dev);
dev->error_state = pci_channel_io_normal;
@@ -390,7 +420,7 @@ static pci_ers_result_t broadcast_error_message(struct pci_dev *dev,
* If the error is reported by an end point, we think this
* error is related to the upstream link of the end point.
*/
- pci_walk_bus(dev->bus, cb, &result_data);
+ aer_pci_walk_bus(dev->bus, cb, &result_data);
}

return result_data.result;
--
2.14.1
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