libxl: In domain death search, start search at first domid we want

From: Ian Jackson <Ian.Jackson@eu.citrix.com>

When domain_death_xswatch_callback needed a further call to
xc_domain_getinfolist it would restart it with the last domain it
found rather than the first one it wants.

If it only wants one it will also only ask for one domain.  The result
would then be that it gets the previous domain again (ie, the previous
one to the one it wants), which still doesn't reveal the answer to the
question, and it would therefore loop again.

It's completely unclear to me why I thought it was a good idea to
start the xc_domain_getinfolist with the last domain previously found
rather than the first one left un-confirmed.  The code has been that
way since it was introduced.

Instead, start each xc_domain_getinfolist at the next domain whose
status we need to check.

We also need to move the test for !evg into the loop, we now need evg
to compute the arguments to getinfolist.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Reported-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Jim Fehlig <jfehlig@suse.com>
Tested-by: Jim Fehlig <jfehlig@suse.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index ad69a8a7197c87bc8ddbd7c9c9bf08eda634f3ae..c904e71cfa6eb2b8f4a1a9cf7e09095327e121ff 100644 (file)
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1168,22 +1168,20 @@ static void domain_death_xswatch_callback(libxl__egc *egc, libxl__ev_xswatch *w,
                                         const char *wpath, const char *epath) {
     EGC_GC;
     libxl_evgen_domain_death *evg;
-    uint32_t domid;
     int rc;
 
     CTX_LOCK;
 
     evg = LIBXL_TAILQ_FIRST(&CTX->death_list);
-    if (!evg) goto out;
-
-    domid = evg->domid;
 
     for (;;) {
+        if (!evg) goto out;
+
         int nentries = LIBXL_TAILQ_NEXT(evg, entry) ? 200 : 1;
         xc_domaininfo_t domaininfos[nentries];
         const xc_domaininfo_t *got = domaininfos, *gotend;
 
-        rc = xc_domain_getinfolist(CTX->xch, domid, nentries, domaininfos);
+        rc = xc_domain_getinfolist(CTX->xch, evg->domid, nentries, domaininfos);
         if (rc == -1) {
             LIBXL__EVENT_DISASTER(egc, "xc_domain_getinfolist failed while"
                                   " processing @releaseDomain watch event",
@@ -1193,8 +1191,10 @@ static void domain_death_xswatch_callback(libxl__egc *egc, libxl__ev_xswatch *w,
         gotend = &domaininfos[rc];
 
         LIBXL__LOG(CTX, LIBXL__LOG_DEBUG, "[evg=%p:%"PRIu32"]"
-                   " from domid=%"PRIu32" nentries=%d rc=%d",
-                   evg, evg->domid, domid, nentries, rc);
+                   " nentries=%d rc=%d %ld..%ld",
+                   evg, evg->domid, nentries, rc,
+                   rc>0 ? (long)domaininfos[0].domain : 0,
+                   rc>0 ? (long)domaininfos[rc-1].domain : 0);
 
         for (;;) {
             if (!evg) {
@@ -1257,7 +1257,6 @@ static void domain_death_xswatch_callback(libxl__egc *egc, libxl__ev_xswatch *w,
         }
 
         assert(rc); /* rc==0 results in us eating all evgs and quitting */
-        domid = gotend[-1].domain;
     }
  all_reported:
  out: