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SubjectRe: [PATCH rdma-next 1/5] RDMA/hns: Implement the disassociate_ucontext API
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On 2018/5/17 23:00, Jason Gunthorpe wrote:
> On Thu, May 17, 2018 at 04:02:49PM +0800, Wei Hu (Xavier) wrote:
>> This patch Implements the IB core disassociate_ucontext API.
>>
>> Signed-off-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>
>> drivers/infiniband/hw/hns/hns_roce_main.c | 36 +++++++++++++++++++++++++++++++
>> 1 file changed, 36 insertions(+)
>>
>> diff --git a/drivers/infiniband/hw/hns/hns_roce_main.c b/drivers/infiniband/hw/hns/hns_roce_main.c
>> index 96fb6a9..7fafe9d 100644
>> +++ b/drivers/infiniband/hw/hns/hns_roce_main.c
>> @@ -33,6 +33,9 @@
>> #include <linux/acpi.h>
>> #include <linux/of_platform.h>
>> #include <linux/module.h>
>> +#include <linux/sched.h>
>> +#include <linux/sched/mm.h>
>> +#include <linux/sched/task.h>
>> #include <rdma/ib_addr.h>
>> #include <rdma/ib_smi.h>
>> #include <rdma/ib_user_verbs.h>
>> @@ -422,6 +425,38 @@ static int hns_roce_port_immutable(struct ib_device *ib_dev, u8 port_num,
>> return 0;
>> }
>>
>> +static void hns_roce_disassociate_ucontext(struct ib_ucontext *ibcontext)
>> +{
>> + struct task_struct *process;
>> + struct mm_struct *mm;
>> +
>> + process = get_pid_task(ibcontext->tgid, PIDTYPE_PID);
>> + if (!process)
>> + return;
>> +
>> + mm = get_task_mm(process);
>> + if (!mm) {
>> + pr_info("no mm, disassociate ucontext is pending task termination\n");
>> + while (1) {
>> + put_task_struct(process);
>> + usleep_range(1000, 2000);
>> + process = get_pid_task(ibcontext->tgid, PIDTYPE_PID);
>> + if (!process || process->state == TASK_DEAD) {
>> + pr_info("disassociate ucontext done, task was terminated\n");
>> + /* if task was dead, need to release the task
>> + * struct.
>> + */
>> + if (process)
>> + put_task_struct(process);
>> + return;
>> + }
>> + }
>> + }
> I don't want to see this boilerplate code copied into every
> driver. Hoist it into the core code, have the disassociate driver callback
> accept a mm_struct parameter, and refactor the other drivers using this.

When the userspace RDMA application process is suspended for some reason
without executing ibv_close_device function,
There will be calltrace as follows when rmmod roce kernel driver ko in
the current version.
It looks like a common problem to every driver and the code segment
above is suitable for every driver.
Pardon me for asking, but if you have any plan to do this?

root@(none)# rmmod
../ko/hns-roce-hw-v2.ko

[ 1222.676069] INFO: task rmmod:1996 blocked for more than 120
seconds.
[ 1222.682423] Not tainted 4.16.0-rc1-29112-ge237d0c-dirty
#15
[ 1222.688507] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[ 1222.696327] rmmod D 0 1996 1951
0x00000000

[ 1222.701807] Call
trace:

[ 1222.704252]
__switch_to+0x9c/0xd8

[ 1222.707644]
__schedule+0x1d8/0x854

[ 1222.711125]
schedule+0x3c/0x9c

[ 1222.714258]
schedule_timeout+0x1dc/0x3f8

[ 1222.718260]
wait_for_common+0x120/0x1e0

[ 1222.722174]
wait_for_completion+0x28/0x34

[ 1222.726264]
ib_uverbs_remove_one+0x29c/0x2bc

[ 1222.730614]
ib_unregister_device+0xe8/0x198

[ 1222.734888] hns_roce_exit+0xb4/0xc4
[hns_roce]

[ 1222.739414] hns_roce_hw_v2_uninit_instance+0x24/0x40
[hns_roce_hw_v2]
[ 1222.745934]
hclge_uninit_client_instance+0x88/0xb8

[ 1222.750803]
hnae3_match_n_instantiate+0xbc/0xd0

[ 1222.755411]
hnae3_unregister_client+0x50/0xb0

[ 1222.759850] hns_roce_hw_v2_exit+0x10/0xd48
[hns_roce_hw_v2]

[ 1222.765501]
SyS_delete_module+0x1e8/0x238

[ 1222.769589]
el0_svc_naked+0x30/0x34


Thanks, Jason

>> + mmput(mm);
>> + put_task_struct(process);
>> +}
> This can't be right, disassociate requires the driver to replace all
> the mmaps it make to user space with the 0 page, I see hns does use
> mmaps, so it must zap them here.
Ok, got it.
>
> Jason
>
> .
>


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