[CRIU] [PATCH] restorer: close log file before detaching from crtools

[Kinsbursky Stanislav]

There is a race between log close by process being restoring and opened file
desctriptors check in zdtm test suite - crtools can exit and compare file
descriptors before detached restored process will perform all the rest tasks
(including close of the log) and execute final system call:

--- dump/sleeping00/8578/dump.fd        2012-02-20 14:31:31.246096000 +0300
+++ dump/sleeping00/8578/restore.fd     2012-02-20 14:31:31.418095999 +0300
@@ -1,4 +1,5 @@

 0 -> /dev/null
 1 -> /dev/null
+1023 -> /root/crtools/test/dump/sleeping00/8578/restore.log
 2 -> /dev/null

The solution is to close log in restorer before final command received. But
this leads to another problem: we have to inform somehow about possible errors
afterwards This is done by forced segmentation fault and looks like this
(dmesg):

pipe00[17373]: segfault at 2ed ip 00000000000002ed sp ffffffffffffffff error
14

Where "ip" is restorer's line number and "sp" is the reason why we failed.

Signed-off-by: Stanislav Kinsbursky <skinsbursky at openvz.org>

---
 restorer.c |   21 +++++++++++++++------
 1 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/restorer.c b/restorer.c
index ea4af04..d25a571 100644
--- a/restorer.c
+++ b/restorer.c
@@ -336,7 +336,7 @@ static u64 restore_mapping(const struct vma_entry *vma_entry)
  */
 long restore_task(struct task_restore_core_args *args)
 {
-	long ret = -1;
+	long ret = -1, line;
 	struct task_entry *task_entry;
 	struct core_entry *core_entry;
 	struct vma_entry *vma_entry;
@@ -722,6 +722,9 @@ long restore_task(struct task_restore_core_args *args)
 	sys_sigaction(SIGCHLD, &args->sigchld_act, NULL);
 
 	cr_wait_dec(&args->task_entries->nr_in_progress);
+
+	sys_close(args->logfd);
+
 	cr_wait_while(&args->task_entries->start, CR_STATE_RESTORE_SIGCHLD);
 
 	/*
@@ -742,13 +745,10 @@ long restore_task(struct task_restore_core_args *args)
 
 	ret = sys_munmap(args->task_entries, TASK_ENTRIES_SIZE);
 	if (ret < 0) {
-		write_num_n(__LINE__);
-		write_num_n(ret);
-		goto core_restore_end;
+		line = __LINE__;
+		goto core_restore_failed;
 	}
 
-	sys_close(args->logfd);
-
 	/*
 	 * Sigframe stack.
 	 */
@@ -773,4 +773,13 @@ core_restore_end:
 	write_num_n(sys_getpid());
 	sys_exit(-1);
 	return -1;
+
+core_restore_failed:
+	asm volatile(
+		"movq %0, %%rsp				\n"
+		"jmp *%1				\n"
+		:
+		: "r"(ret), "r"(line)
+		: );
+	return ret;
 }