[PATCH 3.16 087/366] powerpc/eeh: Fix race with driver un/bind

Ben Hutchings
2018-10-14T23:38:34Z

From: Michael Neuling <mikey@neuling.org>

commit f0295e047fcf52ccb42561fb7de6942f5201b676 upstream.

The current EEH callbacks can race with a driver unbind. This can
result in a backtraces like this:

EEH: Frozen PHB#0-PE#1fc detected
EEH: PE location: S000009, PHB location: N/A
CPU: 2 PID: 2312 Comm: kworker/u258:3 Not tainted 4.15.6-openpower1 #2
Workqueue: nvme-wq nvme_reset_work [nvme]
Call Trace:
dump_stack+0x9c/0xd0 (unreliable)
eeh_dev_check_failure+0x420/0x470
eeh_check_failure+0xa0/0xa4
nvme_reset_work+0x138/0x1414 [nvme]
process_one_work+0x1ec/0x328
worker_thread+0x2e4/0x3a8
kthread+0x14c/0x154
ret_from_kernel_thread+0x5c/0xc8
nvme nvme1: Removing after probe failure status: -19
<snip>
cpu 0x23: Vector: 300 (Data Access) at [c000000ff50f3800]
pc: c0080000089a0eb0: nvme_error_detected+0x4c/0x90 [nvme]
lr: c000000000026564: eeh_report_error+0xe0/0x110
sp: c000000ff50f3a80
msr: 9000000000009033
dar: 400
dsisr: 40000000
current = 0xc000000ff507c000
paca = 0xc00000000fdc9d80 softe: 0 irq_happened: 0x01
pid = 782, comm = eehd
Linux version 4.15.6-openpower1 (smc@smc-desktop) (gcc version 6.4.0 (Buildroot 2017.11.2-00008-g4b6188e)) #2 SM P Tue Feb 27 12:33:27 PST 2018
enter ? for help
eeh_report_error+0xe0/0x110
eeh_pe_dev_traverse+0xc0/0xdc
eeh_handle_normal_event+0x184/0x4c4
eeh_handle_event+0x30/0x288
eeh_event_handler+0x124/0x170
kthread+0x14c/0x154
ret_from_kernel_thread+0x5c/0xc8

The first part is an EEH (on boot), the second half is the resulting
crash. nvme probe starts the nvme_reset_work() worker thread. This
worker thread starts touching the device which see a device error
(EEH) and hence queues up an event in the powerpc EEH worker
thread. nvme_reset_work() then continues and runs
nvme_remove_dead_ctrl_work() which results in unbinding the driver
from the device and hence releases all resources. At the same time,
the EEH worker thread starts doing the EEH .error_detected() driver
callback, which no longer works since the resources have been freed.

This fixes the problem in the same way the generic PCIe AER code (in
drivers/pci/pcie/aer/aerdrv_core.c) does. It makes the EEH code hold
the device_lock() while performing the driver EEH callbacks and
associated code. This ensures either the callbacks are no longer
register, or if they are registered the driver will not be removed
from underneath us.

This has been broken forever. The EEH call backs were first introduced
in 2005 (in 77bd7415610) but it's not clear if a lock was needed back
then.

Fixes: 77bd74156101 ("[PATCH] powerpc: PCI Error Recovery: PPC64 core recovery routines")
Signed-off-by: Michael Neuling <mikey@neuling.org>
Reviewed-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -198,18 +198,18 @@ static void *eeh_report_error(void *data

if (!dev || eeh_dev_removed(edev))
return NULL;
+
+ device_lock(&dev->dev);
dev->error_state = pci_channel_io_frozen;

driver = eeh_pcid_get(dev);
- if (!driver) return NULL;
+ if (!driver) goto out_no_dev;

eeh_disable_irq(dev);

if (!driver->err_handler ||
- !driver->err_handler->error_detected) {
- eeh_pcid_put(dev);
- return NULL;
- }
+ !driver->err_handler->error_detected)
+ goto out;

rc = driver->err_handler->error_detected(dev, pci_channel_io_frozen);

@@ -217,7 +217,10 @@ static void *eeh_report_error(void *data
if (rc == PCI_ERS_RESULT_NEED_RESET) *res = rc;
if (*res == PCI_ERS_RESULT_NONE) *res = rc;

+out:
eeh_pcid_put(dev);
+out_no_dev:
+ device_unlock(&dev->dev);
return NULL;
}

@@ -240,15 +243,14 @@ static void *eeh_report_mmio_enabled(voi
if (!dev || eeh_dev_removed(edev))
return NULL;

+ device_lock(&dev->dev);
driver = eeh_pcid_get(dev);
- if (!driver) return NULL;
+ if (!driver) goto out_no_dev;

if (!driver->err_handler ||
!driver->err_handler->mmio_enabled ||
- (edev->mode & EEH_DEV_NO_HANDLER)) {
- eeh_pcid_put(dev);
- return NULL;
- }
+ (edev->mode & EEH_DEV_NO_HANDLER))
+ goto out;

rc = driver->err_handler->mmio_enabled(dev);

@@ -256,7 +258,10 @@ static void *eeh_report_mmio_enabled(voi
if (rc == PCI_ERS_RESULT_NEED_RESET) *res = rc;
if (*res == PCI_ERS_RESULT_NONE) *res = rc;

+out:
eeh_pcid_put(dev);
+out_no_dev:
+ device_unlock(&dev->dev);
return NULL;
}

@@ -279,19 +284,19 @@ static void *eeh_report_reset(void *data

if (!dev || eeh_dev_removed(edev))
return NULL;
+
+ device_lock(&dev->dev);
dev->error_state = pci_channel_io_normal;

driver = eeh_pcid_get(dev);
- if (!driver) return NULL;
+ if (!driver) goto out_no_dev;

eeh_enable_irq(dev);

if (!driver->err_handler ||
!driver->err_handler->slot_reset ||
- (edev->mode & EEH_DEV_NO_HANDLER)) {
- eeh_pcid_put(dev);
- return NULL;
- }
+ (edev->mode & EEH_DEV_NO_HANDLER))
+ goto out;

rc = driver->err_handler->slot_reset(dev);
if ((*res == PCI_ERS_RESULT_NONE) ||
@@ -299,7 +304,10 @@ static void *eeh_report_reset(void *data
if (*res == PCI_ERS_RESULT_DISCONNECT &&
rc == PCI_ERS_RESULT_NEED_RESET) *res = rc;

+out:
eeh_pcid_put(dev);
+out_no_dev:
+ device_unlock(&dev->dev);
return NULL;
}

@@ -320,10 +328,12 @@ static void *eeh_report_resume(void *dat

if (!dev || eeh_dev_removed(edev))
return NULL;
+
+ device_lock(&dev->dev);
dev->error_state = pci_channel_io_normal;

driver = eeh_pcid_get(dev);
- if (!driver) return NULL;
+ if (!driver) goto out_no_dev;

eeh_enable_irq(dev);

@@ -331,13 +341,15 @@ static void *eeh_report_resume(void *dat
!driver->err_handler->resume ||
(edev->mode & EEH_DEV_NO_HANDLER)) {
edev->mode &= ~EEH_DEV_NO_HANDLER;
- eeh_pcid_put(dev);
- return NULL;
+ goto out;
}

driver->err_handler->resume(dev);

+out:
eeh_pcid_put(dev);
+out_no_dev:
+ device_unlock(&dev->dev);
return NULL;
}

@@ -357,22 +369,25 @@ static void *eeh_report_failure(void *da

if (!dev || eeh_dev_removed(edev))
return NULL;
+
+ device_lock(&dev->dev);
dev->error_state = pci_channel_io_perm_failure;

driver = eeh_pcid_get(dev);
- if (!driver) return NULL;
+ if (!driver) goto out_no_dev;

eeh_disable_irq(dev);

if (!driver->err_handler ||
- !driver->err_handler->error_detected) {
- eeh_pcid_put(dev);
- return NULL;
- }
+ !driver->err_handler->error_detected)
+ goto out;

driver->err_handler->error_detected(dev, pci_channel_io_perm_failure);

+out:
eeh_pcid_put(dev);
+out_no_dev:
+ device_unlock(&dev->dev);
return NULL;
}