rrd_utils: Fix broken recusive directory creation in multithreaded context

Multithreaded applications can issue CREATE commands simultaneously
from several threads. Such commands may require to create directories
from the same root path.

Example:

Thread #1 creates /var/cache/rrd/data/switch/isw61/board0/chip1/port1
Thread #2 creates /var/cache/rrd/data/switch/isw61/board0/chip1/port3

If 2 threads attempt to create the above directories, one thread may
fail when creating a directory already created by the other thread.

The mkdir syscall fails with an error (errno = EEXIST), which causes
the whole CREATE transaction to fail.

Fixed by checking errno after invoking mkdir when creating
directories recursively.

diff --git a/src/rrd_utils.c b/src/rrd_utils.c
index 27b6c3bbde8ead138f39a7f214cd9c10a77fecff..430d92e7d7c9f3d68dfbfb867ae2291b8d2d6aab 100644 (file)
--- a/src/rrd_utils.c
+++ b/src/rrd_utils.c
@@ -222,7 +222,7 @@ int rrd_mkdir_p(const char *pathname_unsafe, mode_t mode)
         return -1;
     }
 #else
-    if (0 != mkdir(pathname, mode)) {
+    if ((mkdir(pathname, mode) != 0) && (errno != EEXIST)) {
         free(pathname);
         return -1;
     }