[ovs-dev] [PATCH V6] windows: Added lockf function and lock PID file

Paul Boca pboca at cloudbasesolutions.com
Tue Jul 5 09:49:02 UTC 2016


If the PID file isn't locked then appctl.py detects it as stale and
bails out without doing anything. Because of this lots of Python tests fail.
Also this protects the PID file from being overwritten.

I used only shared lock, in order to be compatible with Python tests,
which try to acquire the lock exclusively. On Windows if the exclusive lock
is used, than the read access is denied too for other instances of this file.

Signed-off-by: Paul-Daniel Boca <pboca at cloudbasesolutions.com>
---
V2: No changes
V3: No changes
V4: No changes
V5: Removed this patch from Python series.
    Removed unused constants and defined 0xFFFF0000 as constant.
    Updated commit text.
V6: flock returns now the error of GetLastError.
    Also it uses fd parameter instead of the global filep_pidfile.
    Removed unused local variable and unnecessary error message.
---
 lib/daemon-windows.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/lib/daemon-windows.c b/lib/daemon-windows.c
index 8cf0fea..1ac7b12 100644
--- a/lib/daemon-windows.c
+++ b/lib/daemon-windows.c
@@ -18,6 +18,7 @@
 #include "daemon.h"
 #include "daemon-private.h"
 #include <stdio.h>
+#include <io.h>
 #include <stdlib.h>
 #include "dirs.h"
 #include "ovs-thread.h"
@@ -26,6 +27,13 @@
 
 VLOG_DEFINE_THIS_MODULE(daemon_windows);
 
+/* Constants for flock function */
+#define	LOCK_SH	0x0                         /* Shared lock. */
+#define	LOCK_UN	0x80000000                  /* Unlock. Custom value. */
+
+/* High-order 32 bits of byte range to lock */
+#define LOCK_MAX_SIZE 0xFFFF0000
+
 static bool service_create;          /* Was --service specified? */
 static bool service_started;         /* Have we dispatched service to start? */
 
@@ -414,6 +422,31 @@ unlink_pidfile(void)
     }
 }
 
+static int
+flock(FILE* fd, int operation)
+{
+    HANDLE hFile;
+    OVERLAPPED ov = {0};
+
+    hFile = (HANDLE)_get_osfhandle(fileno(fd));
+    if (hFile == INVALID_HANDLE_VALUE) {
+        VLOG_FATAL("Invalid handle value");
+        return ERROR_INVALID_HANDLE;
+    }
+
+    if (operation & LOCK_UN) {
+        if (UnlockFileEx(hFile, 0, 0, LOCK_MAX_SIZE, &ov) == 0) {
+            return GetLastError();
+        }
+    } else {
+        if (LockFileEx(hFile, operation, 0, 0, LOCK_MAX_SIZE, &ov) == FALSE) {
+            return GetLastError();
+        }
+    }
+
+    return ERROR_SUCCESS;
+}
+
 /* If a pidfile has been configured, creates it and stores the running
  * process's pid in it.  Ensures that the pidfile will be deleted when the
  * process exits. */
@@ -444,6 +477,13 @@ make_pidfile(void)
         VLOG_FATAL("Failed to write into the pidfile %s", pidfile);
     }
 
+    error = flock(filep_pidfile, LOCK_SH);
+    if (error) {
+        /* Looks like we failed to acquire the lock. */
+        VLOG_FATAL("%s: fcntl(F_SETLK) failed (%s)", pidfile,
+                   ovs_strerror(error));
+    }
+
     /* Don't close the pidfile till the process exits. */
 }
 
-- 
2.7.2.windows.1



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