[CRIU] [PATCH 03/9] cr-restore: set cr_error to EEXIST if such pid already, exists, v4

[Ruslan Kuprieiev]

Drop it too, please.

19.12.2014 20:14, Ruslan Kuprieiev пишет:
> This is a very common error when using criu.
>
> The problem here is that we need to somehow transfer cr_errno
> from one process to another. I suggest using pipe to give
> one end to children and read cr_errno on other after restore
> is finished.
>
> v2, Pavel suggested putting errno into shared task_entries.
> v3. and he also suggested using cmpxchg
> v4, introduce cr_err helpers in a separate patch
>
> Signed-off-by: Ruslan Kuprieiev <kupruser at gmail.com>
> ---
>   cr-restore.c       | 8 +++++++-
>   include/cr-errno.h | 1 +
>   include/rst_info.h | 1 +
>   3 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/cr-restore.c b/cr-restore.c
> index 93a6ca6..52670fa 100644
> --- a/cr-restore.c
> +++ b/cr-restore.c
> @@ -84,6 +84,9 @@
>   #include "protobuf/siginfo.pb-c.h"
>
>   #include "asm/restore.h"
> +#include "asm/atomic.h"
> +
> +#include "cr-errno.h"
>
>   static struct pstree_item *current;
>
> @@ -1412,6 +1415,7 @@ static int restore_task_with_children(void *_arg)
>   	pid = getpid();
>   	if (current->pid.virt != pid) {
>   		pr_err("Pid %d do not match expected %d\n", pid, current->pid.virt);
> +		set_task_cr_err(EEXIST);
>   		goto err;
>   	}
>
> @@ -1535,8 +1539,10 @@ static int restore_wait_inprogress_tasks()
>
>   	futex_wait_while_gt(np, 0);
>   	ret = (int)futex_get(np);
> -	if (ret < 0)
> +	if (ret < 0) {
> +		set_cr_errno(get_task_cr_err());
>   		return ret;
> +	}
>
>   	return 0;
>   }
> diff --git a/include/cr-errno.h b/include/cr-errno.h
> index 31ddccb..1fd94a0 100644
> --- a/include/cr-errno.h
> +++ b/include/cr-errno.h
> @@ -7,6 +7,7 @@ int get_cr_errno(void);
>   /*
>    * List of symbolic error names:
>    * ESRCH	- no process can be found corresponding to that specified by pid
> + * EEXIST	- process with such pid already exists
>    */
>
>   #define set_task_cr_err(new_err)	atomic_cmpxchg(&task_entries->cr_err, 0, new_err)
> diff --git a/include/rst_info.h b/include/rst_info.h
> index 6b00c50..d509c0c 100644
> --- a/include/rst_info.h
> +++ b/include/rst_info.h
> @@ -10,6 +10,7 @@ struct task_entries {
>   	futex_t nr_in_progress;
>   	futex_t start;
>   	mutex_t	zombie_lock;
> +	atomic_t cr_err;
>   };
>
>   struct fdt {
>