feat(supervisor/posix): pid file

Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>

Author: casaroli

src/samples/supervisor/posix/server/CMakeLists.txt

@@ -13,6 +13,7 @@ add_executable(ocred
     handlers.c
     waiters.c
     runners.c
+    pid_file.c
     ../zcbor_helpers.c
     ../zcbor/src/zcbor_encode.c
     ../zcbor/src/zcbor_decode.c

src/samples/supervisor/posix/server/ocred.c

@@ -26,6 +26,7 @@
 #include "../zcbor_helpers.h"
 #include "waiters.h"
 #include "handlers.h"
+#include "pid_file.h"
 
 #define DEFAULT_PID_FILE   "ocre.pid"
 

src/samples/supervisor/posix/server/pid_file.c

@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/wait.h>
+
+#define BUF_SIZE 64
+
+static int pid_fd = -1;
+
+void ocre_pid_file_release(void)
+{
+	/* TODO: should we release the flock? */
+
+	if (pid_fd >= 0) {
+		close(pid_fd);
+		pid_fd = -1;
+	}
+}
+
+int ocre_pid_file_manage(const char *pid_file)
+{
+	int ret = -1;
+
+	pid_fd = open(pid_file, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
+	if (pid_fd < 0) {
+		fprintf(stderr, "Failed to open PID file '%s': %s\n", pid_file, strerror(errno));
+		return -1;
+	}
+
+	/* TODO: should we really set CLOEXEC? */
+
+	int flags = fcntl(pid_fd, F_GETFD);
+	if (flags < 0) {
+		fprintf(stderr, "Failed to get flags for PID file '%s': %s\n", pid_file, strerror(errno));
+		goto finish;
+	}
+
+	flags |= FD_CLOEXEC;
+
+	if (fcntl(pid_fd, F_SETFD, flags) < 0) {
+		fprintf(stderr, "Failed to set flags for PID file '%s': %s\n", pid_file, strerror(errno));
+		goto finish;
+	}
+
+	/* TODO: maybe check if the process is running? */
+
+	/* TODO: do we need the flock? */
+
+	struct flock fl = {
+		.l_type = F_WRLCK,
+		.l_whence = SEEK_SET,
+		.l_start = 0,
+		.l_len = 0,
+	};
+
+	if (fcntl(pid_fd, F_WRLCK, &fl) < 0) {
+		fprintf(stderr, "Failed to lock PID file '%s': %s\n", pid_file, strerror(errno));
+		goto finish;
+	}
+
+	if (ftruncate(pid_fd, 0) < 0) {
+		fprintf(stderr, "Failed to truncate PID file '%s': %s\n", pid_file, strerror(errno));
+		goto finish;
+	}
+
+	char buf[BUF_SIZE];
+
+	snprintf(buf, BUF_SIZE, "%ld\n", (long)getpid());
+	if (write(pid_fd, buf, strlen(buf)) != (ssize_t)strlen(buf)) {
+		fprintf(stderr, "Failed to write PID file '%s': %s\n", pid_file, strerror(errno));
+		goto finish;
+	}
+
+	ret = 0;
+
+finish:
+	ocre_pid_file_release();
+	return 0;
+}

src/samples/supervisor/posix/server/pid_file.h

@@ -0,0 +1 @@
+int ocre_pid_file_manage(const char *pid_file);