[Xen-devel] [PATCH 4/6] libxl: events: Tear down SIGCHLD machinery on ctx destruction

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

We want to have no fd events registered when we are idle.
Also, we should put back the default SIGCHLD handler.  So:

 * In libxl_ctx_free, use libxl_childproc_setmode to set the mode to
   the default, which is libxl_sigchld_owner_libxl (ie `libxl owns
   SIGCHLD only when it has active children').

   But of course there are no active children at libxl teardown so
   this results in libxl__sigchld_notneeded: the ctx loses its
   interest in SIGCHLD (unsetting the SIGCHLD handler if we were the
   last ctx) and deregisters the per-ctx selfpipe fd.

 * assert that this is the case: ie that we are no longer interested
   in the selfpipe.

Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
---
 tools/libxl/libxl.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 12a1013..785253d 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -162,11 +162,12 @@ int libxl_ctx_free(libxl_ctx *ctx)
     while ((eject = LIBXL_LIST_FIRST(&CTX->disk_eject_evgens)))
         libxl__evdisable_disk_eject(gc, eject);
 
+    libxl_childproc_setmode(CTX,0,0);
     for (i = 0; i < ctx->watch_nslots; i++)
         assert(!libxl__watch_slot_contents(gc, i));
     assert(!libxl__ev_fd_isregistered(&ctx->watch_efd));
     libxl__ev_fd_deregister(gc, &ctx->evtchn_efd);
-    libxl__ev_fd_deregister(gc, &ctx->sigchld_selfpipe_efd);
+    assert(!libxl__ev_fd_isregistered(&ctx->sigchld_selfpipe_efd));
 
     /* Now there should be no more events requested from the application: */
 
-- 
1.7.10.4


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