test/others: refactor loop process

There are several problems with the loop.sh script. First, the code is
duplicated across tests in the so-called 'othres' category. Second, we
need to run it with the 'setsid' utility to make sure that it runs in
a new session. Third, we have to redirect the standard file descriptors
and use the '&' operator to make it run in the background. Finally,
obtaining the PID of the 'loop.sh' process resulted in race condition.

In this patch we replace the loop.sh script with a program that would
address all problems mentioned above. The requirements for this program
are as follows.
- It must be reusable across tests
- It must start a process that is detached from the current shell
- It must wait for the process to start and output its PID

Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>

test/others/.gitignore

@@ -0,0 +1 @@
+loop

test/others/Makefile

@@ -0,0 +1,2 @@
+loop:
+	gcc -Wall loop.c -o loop

test/others/crit/Makefile

@@ -1,4 +1,5 @@
 run: clean
+	@make -C .. loop
 	./test.sh
 
 clean:

test/others/crit/loop.sh

@@ -1,4 +0,0 @@
-#!/bin/bash
-while :; do
-	sleep 1
-done

test/others/crit/test.sh

@@ -8,8 +8,7 @@ source ../env.sh
 images_list=""
 
 function gen_imgs {
-	setsid ./loop.sh < /dev/null &> /dev/null &
-	PID=$!
+	PID=$(../loop)
 	if ! $CRIU dump -v4 -o dump.log -D ./ -t "$PID"; then
 		echo "Failed to checkpoint process $PID"
 		cat dump.log

test/others/criu-coredump/Makefile

@@ -1,4 +1,5 @@
 run: clean
+	@make -C .. loop
 	./test.sh
 
 clean:

test/others/criu-coredump/loop.sh

@@ -1,4 +0,0 @@
-#!/bin/bash
-while :; do
-	sleep 1
-done

test/others/criu-coredump/test.sh

@@ -1,8 +1,7 @@
 source ../env.sh
 
 function gen_imgs {
-	setsid ./loop.sh < /dev/null &> /dev/null &
-	PID=$!
+	PID=$(../loop)
 	if ! $CRIU dump -v4 -o dump.log -D ./ -t "$PID"; then
 		echo "Failed to checkpoint process $PID"
 		cat dump.log

test/others/loop.c

@@ -0,0 +1,63 @@
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+int main(void)
+{
+	pid_t pid;
+	pid_t sid;
+	int res = EXIT_FAILURE;
+	int start_pipe[2];
+
+	if (pipe(start_pipe)) {
+		perror("pipe failed!");
+		goto out;
+	}
+
+	pid = fork();
+	if (pid < 0) {
+		perror("fork failed!");
+		goto out;
+	}
+
+	if (pid == 0) {
+		close(start_pipe[0]);
+
+		sid = setsid();
+		if (sid < 0) {
+			perror("setsid failed!");
+			res = EXIT_FAILURE;
+			write(start_pipe[1], &res, sizeof(res));
+			close(start_pipe[1]);
+			exit(1);
+		}
+
+		// Create a file descriptor for "crit x ./ fds" test
+		open("/dev/null", O_RDONLY);
+
+		chdir("/");
+		close(STDIN_FILENO);
+		close(STDOUT_FILENO);
+		close(STDERR_FILENO);
+
+		res = EXIT_SUCCESS;
+		write(start_pipe[1], &res, sizeof(res));
+		close(start_pipe[1]);
+
+		while(1) {
+			sleep(1);
+		}
+	}
+
+	close(start_pipe[1]);
+	read(start_pipe[0], &res, sizeof(res));
+	close(start_pipe[0]);
+
+ out:
+	if (res == EXIT_SUCCESS)
+		printf("%d\n", pid);
+	return res;
+}

test/others/rpc/Makefile

@@ -7,6 +7,7 @@ LDLIBS +=  -lprotobuf-c
 PYTHON ?= python
 
 run: all
+	@make -C .. loop
 	mkdir -p build
 	chmod a+rwx build
 	rm -f build/status

test/others/rpc/loop.sh

@@ -1,4 +0,0 @@
-#!/bin/bash
-while :; do
-	sleep 1
-done

test/others/rpc/run.sh

@@ -44,12 +44,11 @@ function test_py {
 function test_restore_loop {
 	mkdir -p build/imgs_loop
 
-	title_print "Run loop.sh"
-	setsid ./loop.sh < /dev/null &> build/loop.log &
-	P=${!}
+	title_print "Run loop process"
+	P=$(../loop)
 	echo "pid ${P}"
 
-	title_print "Dump loop.sh"
+	title_print "Dump loop process"
 	# So theoretically '-j' (--shell-job) should not be necessary, but on alpine
 	# this test fails without it.
 	${CRIU} dump -j -v4 -o dump-loop.log -D build/imgs_loop -t ${P}