linux-kernel - Re: [PATCH rdma-next 1/5] RDMA/hns: Implement the disassociate

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Date:   Tue, 22 May 2018 14:21:41 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
Cc:     dledford@...hat.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, xavier.huwei@....com,
        lijun_nudt@....com
Subject: Re: [PATCH rdma-next 1/5] RDMA/hns: Implement the
 disassociate_ucontext API

On Sat, May 19, 2018 at 04:24:40PM +0800, Wei Hu (Xavier) wrote:
> 
> 
> 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@...wei.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?

My plan is to ask you to do it :)

Jason