[PATCH v3 1/3] virpidfile: Add virPidFileReadPathIfLocked func
The function will attempt to read a pid from @path, and store it in
@pid. The @pid will only be set, however, if @path is locked by
virFileLock() at byte 0 and the pid in @path is running.
Signed-off-by: Vasiliy Ulyanov <vulyanov(a)suse.de>
---
src/libvirt_private.syms | 1 +
src/util/virpidfile.c | 34 ++++++++++++++++++++++++++++++++++
src/util/virpidfile.h | 2 ++
3 files changed, 37 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 9bc3d9530b..447ba9d82b 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3070,6 +3070,7 @@ virPidFileRead;
virPidFileReadIfAlive;
virPidFileReadPath;
virPidFileReadPathIfAlive;
+virPidFileReadPathIfLocked;
virPidFileRelease;
virPidFileReleasePath;
virPidFileWrite;
diff --git a/src/util/virpidfile.c b/src/util/virpidfile.c
index 7069f8343d..b8bb455e5e 100644
--- a/src/util/virpidfile.c
+++ b/src/util/virpidfile.c
@@ -302,6 +302,40 @@ int virPidFileReadIfAlive(const char *dir,
return 0;
}
+/**
+ * virPidFileReadPathIfLocked:
+ * @path: path to pidfile
+ * @pid: variable to return pid in
+ *
+ * This will attempt to read a pid from @path, and store it
+ * in @pid. The @pid will only be set, however, if the
+ * pid in @path is running, and @path is locked by virFileLock()
+ * at byte 0. This adds protection against returning a stale pid.
+ *
+ * Returns -1 upon error, or zero on successful
+ * reading of the pidfile. If @path is not locked
+ * or if the PID was not still alive, zero will
+ * be returned, but @pid will be set to -1.
+ */
+int virPidFileReadPathIfLocked(const char *path, pid_t *pid)
+{
+ VIR_AUTOCLOSE fd = -1;
+
+ if ((fd = open(path, O_RDWR)) < 0)
+ return -1;
+
+ if (virFileLock(fd, false, 0, 1, false) >= 0) {
+ /* The file isn't locked. PID is stale. */
+ *pid = -1;
+ return 0;
+ }
+
+ if (virPidFileReadPathIfAlive(path, pid, NULL) < 0)
+ return -1;
+
+ return 0;
+}
+
int virPidFileDeletePath(const char *pidfile)
{
diff --git a/src/util/virpidfile.h b/src/util/virpidfile.h
index fd8013c41e..e84542f298 100644
--- a/src/util/virpidfile.h
+++ b/src/util/virpidfile.h
@@ -48,6 +48,8 @@ int virPidFileReadIfAlive(const char *dir,
const char *name,
pid_t *pid,
const char *binpath) G_GNUC_WARN_UNUSED_RESULT;
+int virPidFileReadPathIfLocked(const char *path,
+ pid_t *pid) G_GNUC_WARN_UNUSED_RESULT;
int virPidFileDeletePath(const char *path);
int virPidFileDelete(const char *dir,
--
2.34.1