Re: [PATCH] target/tcmu: Adds a timeout for the completion of netlink command reply

[Mike Christie <mchristi@redhat.com>]

On 09/13/2017 01:07 AM, Kenjiro Nakayama wrote:
> This patch adds a timeout for the completion of netlink command reply.
> 
> Current code waits for the netlink reply from userspace and the status
> change, but it hangs forever when userspace failed to reply. To fix
> this issue, this patch replace wait_for_completion with
> wait_for_completion_timeout.
> 
> Signed-off-by: Kenjiro Nakayama <nakayamakenjiro@gmail.com>
> ---
>  drivers/target/target_core_user.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
> index 942d094269fb..284294340167 100644
> --- a/drivers/target/target_core_user.c
> +++ b/drivers/target/target_core_user.c
> @@ -1333,7 +1333,12 @@ static int tcmu_wait_genl_cmd_reply(struct tcmu_dev *udev)
>  		return 0;
>  
>  	pr_debug("sleeping for nl reply\n");
> -	wait_for_completion(&nl_cmd->complete);
> +	ret = wait_for_completion_timeout(&nl_cmd->complete,
> +			msecs_to_jiffies(3000));
> +	if (!ret) {
> +		printk(KERN_ERR "timeout waiting for nl reply from userspace\n");
> +		return -ETIME;
> +	}
>  

30 sec is too short. You have to make this configurable, because tcmu
does not know how long it will take userspace to complete the requested
task. For a clustered device it can take a while.