[CRIU] [PATCH 3/8] cr-restore: set cr_error to EEXIST if such pid already exists, v2

[Ruslan Kuprieiev]

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.

Signed-off-by: Ruslan Kuprieiev <kupruser at gmail.com>
---
 cr-restore.c       | 7 ++++++-
 include/cr-errno.h | 1 +
 include/rst_info.h | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/cr-restore.c b/cr-restore.c
index 93a6ca6..60641d9 100644
--- a/cr-restore.c
+++ b/cr-restore.c
@@ -85,6 +85,8 @@
 
 #include "asm/restore.h"
 
+#include "cr-errno.h"
+
 static struct pstree_item *current;
 
 static int restore_task_with_children(void *);
@@ -1412,6 +1414,7 @@ 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);
+		task_entries->cr_err = EEXIST;
 		goto err;
 	}
 
@@ -1535,8 +1538,10 @@ static int restore_wait_inprogress_tasks()
 
 	futex_wait_while_gt(np, 0);
 	ret = (int)futex_get(np);
-	if (ret < 0)
+	if (ret < 0) {
+		cr_errno = task_entries->cr_err;
 		return ret;
+	}
 
 	return 0;
 }
diff --git a/include/cr-errno.h b/include/cr-errno.h
index bec72a8..f86bba8 100644
--- a/include/cr-errno.h
+++ b/include/cr-errno.h
@@ -4,6 +4,7 @@ extern int cr_errno;
 /*
  * List of symbolic error names:
  * ESRCH	- no process can be found corresponding to that specified by pid
+ * EEXIST	- process with such pid already exists
  */
 
 #endif /* __CR_ERRNO_H__ */
diff --git a/include/rst_info.h b/include/rst_info.h
index 6b00c50..cec0144 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;
+	int cr_err;
 };
 
 struct fdt {
-- 
1.9.3