libxc: suspend: Rename, improve xc_suspend_evtchn_init

xc_suspend_evtchn_init expects to eat the first event on the xce.  If
the xce is used for any other purpose then this can break.  Document
this fact and rename the function to xc_suspend_evtchn_init_exclusive.
(I haven't checked the call sites for improper shared use of the xce.)

Provide a corresponding xc_suspend_evtchn_init_sane which doesn't try
to eat an event, and instead leaves the caller the ability to
demultiplex.

Also document that xc_await_suspend needs exclusive use of the xce.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---
v3: Drop spurious addition of #include <assert.h>

diff --git a/tools/libxc/xc_suspend.c b/tools/libxc/xc_suspend.c
index 1ace411860cb9128702bf0ebd5b1369c1cfa41a0..eed3be22ed72b78dabf5f0df2d37494a084c1034 100644 (file)
--- a/tools/libxc/xc_suspend.c
+++ b/tools/libxc/xc_suspend.c
@@ -102,7 +102,7 @@ int xc_suspend_evtchn_release(xc_interface *xch, xc_evtchn *xce, int domid, int
     return unlock_suspend_event(xch, domid);
 }
 
-int xc_suspend_evtchn_init(xc_interface *xch, xc_evtchn *xce, int domid, int port)
+int xc_suspend_evtchn_init_sane(xc_interface *xch, xc_evtchn *xce, int domid, int port)
 {
     int rc, suspend_evtchn = -1;
 
@@ -121,9 +121,6 @@ int xc_suspend_evtchn_init(xc_interface *xch, xc_evtchn *xce, int domid, int por
         goto cleanup;
     }
 
-    /* event channel is pending immediately after binding */
-    xc_await_suspend(xch, xce, suspend_evtchn);
-
     return suspend_evtchn;
 
 cleanup:
@@ -132,3 +129,17 @@ cleanup:
 
     return -1;
 }
+
+int xc_suspend_evtchn_init_exclusive(xc_interface *xch, xc_evtchn *xce, int domid, int port)
+{
+    int suspend_evtchn;
+
+    suspend_evtchn = xc_suspend_evtchn_init_sane(xch, xce, domid, port);
+    if (suspend_evtchn < 0)
+        return suspend_evtchn;
+
+    /* event channel is pending immediately after binding */
+    xc_await_suspend(xch, xce, suspend_evtchn);
+
+    return suspend_evtchn;
+}

diff --git a/tools/libxc/xenguest.h b/tools/libxc/xenguest.h
index a0e30e1c986d7d69c54074560d1081e99887f0be..ce5456c1787b118d10b1c67e39a4476fcf2819cc 100644 (file)
--- a/tools/libxc/xenguest.h
+++ b/tools/libxc/xenguest.h
@@ -256,10 +256,21 @@ int xc_hvm_build_target_mem(xc_interface *xch,
 
 int xc_suspend_evtchn_release(xc_interface *xch, xc_evtchn *xce, int domid, int suspend_evtchn);
 
-int xc_suspend_evtchn_init(xc_interface *xch, xc_evtchn *xce, int domid, int port);
+/**
+ * This function eats the initial notification.
+ * xce must not be used for anything else
+ */
+int xc_suspend_evtchn_init_exclusive(xc_interface *xch, xc_evtchn *xce, int domid, int port);
 
+/* xce must not be used for anything else */
 int xc_await_suspend(xc_interface *xch, xc_evtchn *xce, int suspend_evtchn);
 
+/**
+ * The port will be signaled immediately after this call
+ * The caller should check the domain status and look for the next event
+ */
+int xc_suspend_evtchn_init_sane(xc_interface *xch, xc_evtchn *xce, int domid, int port);
+
 int xc_get_bit_size(xc_interface *xch,
                     const char *image_name, const char *cmdline,
                     const char *features, int *type);

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 55f74b23d8f49d870721bd31484ba869ecd678f6..4b4285613f19f4a98450b9d3adf6782825e44e06 100644 (file)
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -1358,7 +1358,7 @@ void libxl__domain_suspend(libxl__egc *egc, libxl__domain_suspend_state *dss)
 
         if (port >= 0) {
             dss->suspend_eventchn =
-                xc_suspend_evtchn_init(CTX->xch, dss->xce, dss->domid, port);
+                xc_suspend_evtchn_init_exclusive(CTX->xch, dss->xce, dss->domid, port);
 
             if (dss->suspend_eventchn < 0)
                 LOG(WARN, "Suspend event channel initialization failed");

diff --git a/tools/misc/xen-hptool.c b/tools/misc/xen-hptool.c
index f8570f25cd8d3c95694b0ec2324fa3ac1ab46d52..1923be93ba71d177a5af9e33e129aac414bfd5c6 100644 (file)
--- a/tools/misc/xen-hptool.c
+++ b/tools/misc/xen-hptool.c
@@ -111,7 +111,7 @@ static int suspend_guest(xc_interface *xch, xc_evtchn *xce, int domid, int *evtc
         fprintf(stderr, "DOM%d: No suspend port, try live migration\n", domid);
         goto failed;
     }
-    suspend_evtchn = xc_suspend_evtchn_init(xch, xce, domid, port);
+    suspend_evtchn = xc_suspend_evtchn_init_exclusive(xch, xce, domid, port);
     if (suspend_evtchn < 0)
     {
         fprintf(stderr, "Suspend evtchn initialization failed\n");

diff --git a/tools/python/xen/lowlevel/checkpoint/libcheckpoint.c b/tools/python/xen/lowlevel/checkpoint/libcheckpoint.c
index 01c0d47c126864bf4e52c08880973f7df06028db..817d2720dc1e7904a34d28183ec030911093f1d5 100644 (file)
--- a/tools/python/xen/lowlevel/checkpoint/libcheckpoint.c
+++ b/tools/python/xen/lowlevel/checkpoint/libcheckpoint.c
@@ -360,7 +360,7 @@ static int setup_suspend_evtchn(checkpoint_state* s)
     return -1;
   }
 
-  s->suspend_evtchn = xc_suspend_evtchn_init(s->xch, s->xce, s->domid, port);
+  s->suspend_evtchn = xc_suspend_evtchn_init_exclusive(s->xch, s->xce, s->domid, port);
   if (s->suspend_evtchn < 0) {
       s->errstr = "failed to bind suspend event channel";
       return -1;

diff --git a/tools/xcutils/xc_save.c b/tools/xcutils/xc_save.c
index 654c9c25cde12e594aa9925b0634266ba3674567..aaa09b0df79f58ab0e6000c8fa3201be0aeb2060 100644 (file)
--- a/tools/xcutils/xc_save.c
+++ b/tools/xcutils/xc_save.c
@@ -199,7 +199,7 @@ main(int argc, char **argv)
         else
         {
             si.suspend_evtchn =
-              xc_suspend_evtchn_init(si.xch, si.xce, si.domid, port);
+              xc_suspend_evtchn_init_exclusive(si.xch, si.xce, si.domid, port);
 
             if (si.suspend_evtchn < 0)
                 warnx("suspend event channel initialization failed, "