X-Git-Url: http://git.annexia.org/?a=blobdiff_plain;f=src%2Fguestfs.pod;h=341321f136fe33201cb63a27f499935519a786ee;hb=d28d76b4fba3afe18757ab848346e8123a8bcae1;hp=915d8605a3759f94a7a0b854f1f7b9be03abecb9;hpb=2b5fbc882a0a79646b668c7b95442f0b3673d63a;p=libguestfs.git

diff --git a/src/guestfs.pod b/src/guestfs.pod
index 915d860..341321f 100644
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -1949,6 +1949,45 @@ this example, messages are directed to syslog:
      syslog (priority, "event 0x%lx: %s", event, buf);
  }
 
+=head1 CANCELLING LONG TRANSFERS
+
+Some operations can be cancelled by the caller while they are in
+progress.  Currently only operations that involve uploading or
+downloading data can be cancelled (technically: operations that have
+C<FileIn> or C<FileOut> parameters in the generator).
+
+=head2 guestfs_user_cancel
+
+ void guestfs_user_cancel (guestfs_h *g);
+
+C<guestfs_user_cancel> cancels the current upload or download
+operation.
+
+Unlike most other libguestfs calls, this function is signal safe and
+thread safe.  You can call it from a signal handler or from another
+thread, without needing to do any locking.
+
+The transfer that was in progress (if there is one) will stop shortly
+afterwards, and will return an error.  The errno (see
+L</guestfs_last_errno>) is set to C<EINTR>, so you can test for this
+to find out if the operation was cancelled or failed because of
+another error.
+
+No cleanup is performed: for example, if a file was being uploaded
+then after cancellation there may be a partially uploaded file.  It is
+the caller's responsibility to clean up if necessary.
+
+There are two common places that you might call C<guestfs_user_cancel>.
+
+In an interactive text-based program, you might call it from a
+C<SIGINT> signal handler so that pressing C<^C> cancels the current
+operation.  (You also need to call L</guestfs_set_pgroup> so that
+child processes don't receive the C<^C> signal).
+
+In a graphical program, when the main thread is displaying a progress
+bar with a cancel button, wire up the cancel button to call this
+function.
+
 =head1 PRIVATE DATA AREA
 
 You can attach named pieces of private data to the libguestfs handle,
@@ -2658,6 +2697,11 @@ Automated tests of the C API.
 The L<virt-cat(1)>, L<virt-filesystems(1)> and L<virt-ls(1)> commands
 and documentation.
 
+=item C<caution>
+
+Safety and liveness tests of components that libguestfs depends upon
+(not of libguestfs itself).  Mainly this is for qemu and the kernel.
+
 =item C<contrib>
 
 Outside contributions, experimental parts.