Fix: sessiond: freeze on channel creation on restart

[lttng-tools.git] / src / common / lockfile.cpp

diff --git a/src/common/lockfile.cpp b/src/common/lockfile.cpp
index 5dce37d6fd2f5aa7f5ad1bc763dad987957eb117..3e972fbac597baff8b915838553ae2581540baaa 100644 (file)
--- a/src/common/lockfile.cpp
+++ b/src/common/lockfile.cpp
@@ -10,49 +10,93 @@
 #include <common/lockfile.hpp>
 #include <common/macros.hpp>
 
+#include <fcntl.h>
+
 #ifdef HAVE_FLOCK
 
+#include <sys/file.h>
+
+static int lock_file(const char *filepath, int fd)
+{
+       int ret;
+
+       /*
+        * Attempt to lock the file. If this fails, there is
+        * already a process using the same lock file running
+        * and we should exit.
+        */
+       ret = flock(fd, LOCK_EX | LOCK_NB);
+       if (ret == -1) {
+               /* EWOULDBLOCK are expected if the file is locked: don't spam the logs. */
+               if (errno != EWOULDBLOCK) {
+                       PERROR("Failed to apply lock on lock file: file_path=`%s`", filepath);
+               }
+       }
+
+       return ret;
+}
+
 #else /* HAVE_FLOCK */
 
-#include <fcntl.h>
+static int lock_file(const char *filepath, int fd)
+{
+       int ret;
+       struct flock lock = {};
+
+       lock.l_whence = SEEK_SET;
+       lock.l_type = F_WRLCK;
+
+       /*
+        * Attempt to lock the file. If this fails, there is
+        * already a process using the same lock file running
+        * and we should exit.
+        */
+       ret = fcntl(fd, F_SETLK, &lock);
+       if (ret == -1) {
+               /* EAGAIN and EACCESS are expected if the file is locked: don't spam the logs. */
+               if (errno != EAGAIN && errno != EACCES) {
+                       PERROR("Failed to set lock on lock file: file_path=`%s`", filepath);
+               }
+       }
+
+       return ret;
+}
+
+#endif /* HAVE_FLOCK */
 
 int utils_create_lock_file(const char *filepath)
 {
-       int ret;
-       int fd;
-       struct flock lock;
+       int ret, fd;
 
        LTTNG_ASSERT(filepath);
 
-       memset(&lock, 0, sizeof(lock));
        fd = open(filepath, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
        if (fd < 0) {
-               PERROR("open lock file %s", filepath);
+               PERROR("Failed to open lock file `%s`", filepath);
                fd = -1;
                goto error;
        }
 
        /*
-        * Attempt to lock the file. If this fails, there is
-        * already a process using the same lock file running
-        * and we should exit.
+        * Attempt to lock the file. If this fails, there is already a process using the same lock
+        * file running and we should exit.
+        *
+        * lock_file is chosen based on the build configuration, see implementations above.
         */
-       lock.l_whence = SEEK_SET;
-       lock.l_type = F_WRLCK;
-
-       ret = fcntl(fd, F_SETLK, &lock);
+       ret = lock_file(filepath, fd);
        if (ret == -1) {
-               PERROR("fcntl lock file");
-               ERR("Could not get lock file %s, another instance is running.", filepath);
+               ERR("Could not get lock file `%s`, another instance is running.", filepath);
+
                if (close(fd)) {
-                       PERROR("close lock file");
+                       PERROR("Failed to close lock file fd: fd=%d", fd);
                }
+
                fd = ret;
                goto error;
        }
 
+       DBG_FMT("Acquired lock file: file_path={}", filepath);
+
 error:
        return fd;
-}
-
-#endif /* HAVE_FLOCK */
\ No newline at end of file
+}
\ No newline at end of file