Re: [PATCH] powerpc/eeh: Fix race with driver un/bind

[Greg KH <greg@kroah.com>]

On Mon, Apr 23, 2018 at 11:03:30AM +1000, Michael Neuling wrote:
> 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")
> Cc: stable@vger.kernel.org # v4.9, v4.14
> 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>
> 
> ---
> Greg, this is a backport since the upstream patch didn't apply to v4.9
> and v4.14.

Now applied, thanks.

greg k-h