Re: [PATCH] IB: fix task hanging on error recovery

Kleber Sacilotto de Souza
2012-11-01T17:53:55Z

On 11/01/2012 01:30 PM, Hal Rosenstock wrote:
> On 11/1/2012 11:12 AM, Or Gerlitz wrote:
>> On 19/10/2012 23:58, Kleber Sacilotto de Souza wrote:
>>> During PCI error recovery, the calls to wait_for_completion() in the
>>> infiniband core path can hang waiting for some tasks that will never
>>> complete, since the hardware is nonfunctional.
>>>
>>> INFO: task eehd:16029 blocked for more than 120 seconds.
>>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
>>> message.
>>> eehd D 0000000000000000 9664 16029 3093 0x00000080
>>> Call Trace:
>>> [c0000000af8430e0] [c0000000be05e200] 0xc0000000be05e200 (unreliable)
>>> [c0000000af8432b0] [c000000000014070] .__switch_to+0x130/0x250
>>> [c0000000af843360] [c000000000777c5c] .__schedule+0x40c/0x920
>>> [c0000000af843600] [c000000000775a10] .schedule_timeout+0x210/0x260
>>> [c0000000af8436e0] [c000000000777658] .wait_for_common+0xf8/0x210
>>> [c0000000af8437c0] [d000000004113538]
>>> .ib_unregister_mad_agent+0x498/0x690 [ib_mad]
>>> [c0000000af8438c0] [d0000000042c01f4] .ib_sa_remove_one+0xe4/0x180
>>> [ib_sa]
>>> [c0000000af843970] [d0000000040952e8] .ib_unregister_device+0x78/0x170
>>> [ib_core]
>>> [c0000000af843a10] [d000000004183290] .mlx4_ib_remove+0x40/0x1f0
>>> [mlx4_ib]
>>> [c0000000af843ab0] [d000000003f6ab54] .mlx4_remove_device+0xd4/0x110
>>> [mlx4_core]
>>> [c0000000af843b40] [d000000003f6abfc]
>>> .mlx4_unregister_device+0x6c/0xf0 [mlx4_core]
>>> [c0000000af843be0] [d000000003f6f19c] .mlx4_remove_one+0x10c/0x3a0
>>> [mlx4_core]
>>> [c0000000af843c80] [d000000003f6f448] .mlx4_pci_err_detected+0x18/0x40
>>> [mlx4_core]
>>> [c0000000af843d00] [c000000000058a50] .eeh_report_error+0x70/0xe0
>>> [c0000000af843d90] [c0000000003e4d94] .pci_walk_bus+0xa4/0x140
>>> [c0000000af843e50] [c000000000058628] .handle_eeh_events+0x1f8/0x480
>>> [c0000000af843f00] [c000000000058dfc] .eeh_event_handler+0x13c/0x1e0
>>> [c0000000af843f90] [c00000000002031c] .kernel_thread+0x54/0x70
>>>
>>> This patch fixes the issue by replacing the calls to
>>> wait_for_completion() by wait_for_completion_timeout(), providing a
>>> timeout of 5 seconds to wait for the normal completion of the task.
>>>
>>> Signed-off-by: Kleber Sacilotto de Souza<klebers-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
>>> ---
>>> drivers/infiniband/core/addr.c | 2 +-
>>> drivers/infiniband/core/cm.c | 2 +-
>>> drivers/infiniband/core/cma.c | 4 ++--
>>> drivers/infiniband/core/iwcm.c | 2 +-
>>> drivers/infiniband/core/mad.c | 4 ++--
>>> drivers/infiniband/core/mad_rmpp.c | 2 +-
>>> drivers/infiniband/core/multicast.c | 4 ++--
>>> drivers/infiniband/core/sa_query.c | 2 +-
>> for all the above files, your patch makes sense, since the
>> completion/refcount logic
>> relate to waiting for event that needs to come from the device.
> Is this a fix or a workaround for some other underlying issue which
> needs fixing ?
>
> What happens when modules are reloaded after this ? Do things still work
> ? Are resources lost ?

After the error is recovered, the IB devices resume their normal operations,
and the modules can be reloaded successfully.

>
> -- Hal
>
>>> drivers/infiniband/core/ucm.c | 2 +-
>>> drivers/infiniband/core/ucma.c | 2 +-
>> On these files, as far as I understand this code from quick looking, I'm
>> not sure on what
>> exactly the completion objects protects, Sean?
>>
>> Or.
>>
>>> drivers/infiniband/core/uverbs_main.c | 4 ++--
>>
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--
Kleber Sacilotto de Souza
IBM Linux Technology Center