ctdb-common: Add routines to manage PID file

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12287

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>

1 files changed, 143 insertions, 0 deletions

diff --git a/ctdb/common/pidfile.c b/ctdb/common/pidfile.c
new file mode 100644
index 00000000000..b3f29e3f07d
--- /dev/null
+++ b/ctdb/common/pidfile.c
@@ -0,0 +1,143 @@
+/*
+   Create and remove pidfile
+
+   Copyright (C) Amitay Isaacs  2016
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "replace.h"
+#include "system/filesys.h"
+
+#include <talloc.h>
+
+#include "common/pidfile.h"
+
+struct pidfile_context {
+	const char *pidfile;
+	int fd;
+	pid_t pid;
+};
+
+static int pidfile_context_destructor(struct pidfile_context *pid_ctx);
+
+int pidfile_create(TALLOC_CTX *mem_ctx, const char *pidfile,
+		   struct pidfile_context **result)
+{
+	struct pidfile_context *pid_ctx;
+	struct flock lck;
+	char tmp[64];
+	int fd, ret = 0;
+	int len;
+	ssize_t nwritten;
+
+	pid_ctx = talloc_zero(mem_ctx, struct pidfile_context);
+	if (pid_ctx == NULL) {
+		return ENOMEM;
+	}
+
+	pid_ctx->pidfile = talloc_strdup(pid_ctx, pidfile);
+	if (pid_ctx->pidfile == NULL) {
+		ret = ENOMEM;
+		goto fail;
+	}
+
+	pid_ctx->pid = getpid();
+
+	fd = open(pidfile, O_CREAT|O_WRONLY|O_NONBLOCK, 0644);
+	if (fd == -1) {
+		ret = errno;
+		goto fail;
+	}
+
+	pid_ctx->fd = fd;
+
+	lck = (struct flock) {
+		.l_type = F_WRLCK,
+		.l_whence = SEEK_SET,
+	};
+
+	do {
+		ret = fcntl(fd, F_SETLK, &lck);
+	} while ((ret == -1) && (errno == EINTR));
+
+	if (ret != 0) {
+		ret = errno;
+		goto fail;
+	}
+
+	do {
+		ret = ftruncate(fd, 0);
+	} while ((ret == -1) && (errno == EINTR));
+
+	if (ret == -1) {
+		ret = EIO;
+		goto fail_unlink;
+	}
+
+	len = snprintf(tmp, sizeof(tmp), "%u\n", pid_ctx->pid);
+	if (len < 0) {
+		ret = EIO;
+		goto fail_unlink;
+	}
+
+	do {
+		nwritten = write(fd, tmp, len);
+	} while ((nwritten == -1) && (errno == EINTR));
+
+	if ((nwritten == -1) || (nwritten != len)) {
+		ret = EIO;
+		goto fail_unlink;
+	}
+
+	talloc_set_destructor(pid_ctx, pidfile_context_destructor);
+
+	*result = pid_ctx;
+	return 0;
+
+fail_unlink:
+	unlink(pidfile);
+	close(fd);
+
+fail:
+	talloc_free(pid_ctx);
+	return ret;
+}
+
+static int pidfile_context_destructor(struct pidfile_context *pid_ctx)
+{
+	struct flock lck;
+	int ret;
+
+	if (getpid() != pid_ctx->pid) {
+		return 0;
+	}
+
+	lck = (struct flock) {
+		.l_type = F_UNLCK,
+		.l_whence = SEEK_SET,
+	};
+
+	(void) unlink(pid_ctx->pidfile);
+
+	do {
+		ret = fcntl(pid_ctx->fd, F_SETLK, &lck);
+	} while ((ret == -1) && (errno == EINTR));
+
+	do {
+		ret = close(pid_ctx->fd);
+	} while ((ret == -1) && (errno == EINTR));
+
+	return 0;
+}