[Xen-devel] [PATCH 29/29] libxl: cancellation: Make datacopiers cancellable

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

libxl__datacopier_* can now actually generate a callback with
rc==CANCELLED.

This provides cancellation during some corner cases, including (at
least) copying the device model data during the end of domain save.

Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
---
v2: New in this version of the series.
---
 tools/libxl/libxl_aoutils.c  |   16 ++++++++++++++++
 tools/libxl/libxl_internal.h |    1 +
 2 files changed, 17 insertions(+)

diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
index ece7981..919bf12 100644
--- a/tools/libxl/libxl_aoutils.c
+++ b/tools/libxl/libxl_aoutils.c
@@ -103,6 +103,7 @@ static void xswait_report_error(libxl__egc *egc, 
libxl__xswait_state *xswa,
 void libxl__datacopier_init(libxl__datacopier_state *dc)
 {
     assert(dc->ao);
+    libxl__ao_cancellable_init(&dc->cancel);
     libxl__ev_fd_init(&dc->toread);
     libxl__ev_fd_init(&dc->towrite);
     LIBXL_TAILQ_INIT(&dc->bufs);
@@ -113,6 +114,7 @@ void libxl__datacopier_kill(libxl__datacopier_state *dc)
     STATE_AO_GC(dc->ao);
     libxl__datacopier_buf *buf, *tbuf;
 
+    libxl__ao_cancellable_deregister(&dc->cancel);
     libxl__ev_fd_deregister(gc, &dc->toread);
     libxl__ev_fd_deregister(gc, &dc->towrite);
     LIBXL_TAILQ_FOREACH_SAFE(buf, &dc->bufs, entry, tbuf)
@@ -196,6 +198,15 @@ static int datacopier_pollhup_handled(libxl__egc *egc,
     return 0;
 }
 
+static void datacopier_cancel(libxl__egc *egc, libxl__ao_cancellable *cancel,
+                              int rc)
+{
+    libxl__datacopier_state *dc = CONTAINER_OF(cancel, *dc, cancel);
+    STATE_AO_GC(dc->ao);
+
+    datacopier_callback(egc, dc, rc, -1, 0);
+}
+
 static void datacopier_readable(libxl__egc *egc, libxl__ev_fd *ev,
                                 int fd, short events, short revents) {
     libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, toread);
@@ -312,6 +323,11 @@ int libxl__datacopier_start(libxl__datacopier_state *dc)
 
     libxl__datacopier_init(dc);
 
+    dc->cancel.ao = ao;
+    dc->cancel.callback = datacopier_cancel;
+    rc = libxl__ao_cancellable_register(&dc->cancel);
+    if (rc) goto out;
+
     rc = libxl__ev_fd_register(gc, &dc->toread, datacopier_readable,
                                dc->readfd, POLLIN);
     if (rc) goto out;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 29a612c..9d9f376 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2594,6 +2594,7 @@ struct libxl__datacopier_state {
     libxl__datacopier_callback *callback;
     libxl__datacopier_callback *callback_pollhup;
     /* remaining fields are private to datacopier */
+    libxl__ao_cancellable cancel;
     libxl__ev_fd toread, towrite;
     ssize_t used;
     LIBXL_TAILQ_HEAD(libxl__datacopier_bufs, libxl__datacopier_buf) bufs;
-- 
1.7.10.4


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