Work around LVM related race condition when using --force with LVM

If an "lvremove" is immediately followed by an "lvcreate" for an LV
with the same name, "mkswap" (and maybe other commands) occasionally
fail with "Device or resource busy".

Work around it by using sync and sleep.

NEWS.markdown

@@ -23,6 +23,11 @@ Bug Fixes
   Thanks Santiago Vila for the bug report and patch! (Closes Debian
   bug report #764625)
 * Fixes typo found by Lintian.
+* Work around LVM related race condition when using --force with LVM:
+  If an "lvremove" is immediately followed by an "lvcreate" for an LV
+  with the same name, "mkswap" (and maybe other commands) occasionally
+  fail with "Device or resource busy". Work around it by using sync
+  and sleep.
 
 Distribution Releases Changes
 -----------------------------

bin/xen-create-image

@@ -3066,6 +3066,10 @@ sub createLVMBits
                     logprint(
                         "Removing $lvm_disk - since we're forcing the install\n");
                     runCommand("lvremove --force $lvm_disk", \%CONFIG);
+                    runCommand("sync", \%CONFIG);
+                    logprint(
+                        "Sleeping a few seconds to avoid LVM race conditions...\n");
+                    sleep(3);
                 } else {
                     fail("ERROR: Xen guest $CONFIG{'hostname'} appears to be running.\nAborting.\n");
                 }

debian/changelog

@@ -21,6 +21,7 @@ xen-tools (4.6.3~dev-1) UNRELEASED; urgency=medium
     + Support situations where distributions (e.g. Squeeze) might be EoL,
       but its archive signing key is still not removed from the default
       keyring.
+    + Workaround LVM related race condition when using --force with LVM.
   * Declare compliance with Debian Policy 3.9.8. (No changes needed.)
   * Use NEWS.markdown as upstream changelog, don't install it as docs.
   * Switch many URLs (upstream and in packaging) to https:// and update