[Xen-devel] [PATCH 26/28] libxl: cancellation: Cancel libxc save/restore

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

Register the the save/restore helper interface with the cancellation
machinery.  When we are informed that save/restore should be
cancelled, we make a note of the that in our rc variable, and send the
helper a SIGTERM.  It will die in due course.

Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
v2: New in this version of the series.
---
 tools/libxl/libxl_internal.h     |    1 +
 tools/libxl/libxl_save_callout.c |   25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 465cdda..883daae 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2638,6 +2638,7 @@ typedef struct libxl__save_helper_state {
     int rc;
     int completed; /* retval/errnoval valid iff completed */
     int retval, errnoval; /* from xc_domain_save / xc_domain_restore */
+    libxl__ao_cancellable cancel;
     libxl__carefd *pipes[2]; /* 0 = helper's stdin, 1 = helper's stdout */
     libxl__ev_fd readable;
     libxl__ev_child child;
diff --git a/tools/libxl/libxl_save_callout.c b/tools/libxl/libxl_save_callout.c
index 1d584f1..d9fa0d2 100644
--- a/tools/libxl/libxl_save_callout.c
+++ b/tools/libxl/libxl_save_callout.c
@@ -32,6 +32,7 @@ static void run_helper(libxl__egc *egc, 
libxl__save_helper_state *shs,
                        const unsigned long *argnums, int num_argnums);
 
 static void helper_failed(libxl__egc*, libxl__save_helper_state *shs, int rc);
+static void helper_cancel(libxl__egc *egc, libxl__ao_cancellable*, int rc);
 static void helper_stdout_readable(libxl__egc *egc, libxl__ev_fd *ev,
                                    int fd, short events, short revents);
 static void helper_exited(libxl__egc *egc, libxl__ev_child *ch,
@@ -166,9 +167,15 @@ static void run_helper(libxl__egc *egc, 
libxl__save_helper_state *shs,
     shs->rc = 0;
     shs->completed = 0;
     shs->pipes[0] = shs->pipes[1] = 0;
+    libxl__ao_cancellable_init(&shs->cancel);
     libxl__ev_fd_init(&shs->readable);
     libxl__ev_child_init(&shs->child);
 
+    shs->cancel.ao = shs->ao;
+    shs->cancel.callback = helper_cancel;
+    rc = libxl__ao_cancellable_register(&shs->cancel);
+    if (rc) goto out;
+
     shs->stdin_what = GCSPRINTF("domain %"PRIu32" save/restore helper"
                                 " stdin pipe", domid);
     shs->stdout_what = GCSPRINTF("domain %"PRIu32" save/restore helper"
@@ -262,6 +269,23 @@ static void helper_failed(libxl__egc *egc, 
libxl__save_helper_state *shs,
     sendsig(gc, shs, SIGKILL);
 }
 
+static void helper_cancel(libxl__egc *egc, libxl__ao_cancellable *cancel,
+                          int rc)
+{
+    libxl__save_helper_state *shs = CONTAINER_OF(cancel, *shs, cancel);
+    STATE_AO_GC(shs->ao);
+
+    if (!libxl__ev_child_inuse(&shs->child)) {
+        helper_failed(egc, shs, rc);
+        return;
+    }
+
+    if (!shs->rc)
+        shs->rc = rc;
+
+    sendsig(gc, shs, SIGTERM);
+}
+
 static void helper_stdout_readable(libxl__egc *egc, libxl__ev_fd *ev,
                                    int fd, short events, short revents)
 {
@@ -332,6 +356,7 @@ static void helper_done(libxl__egc *egc, 
libxl__save_helper_state *shs)
 {
     STATE_AO_GC(shs->ao);
 
+    libxl__ao_cancellable_deregister(&shs->cancel);
     libxl__ev_fd_deregister(gc, &shs->readable);
     libxl__carefd_close(shs->pipes[0]);  shs->pipes[0] = 0;
     libxl__carefd_close(shs->pipes[1]);  shs->pipes[1] = 0;
-- 
1.7.10.4


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