[Xen-devel] [PATCH 4/4] libxl: improve subprocess handling

[Jim Fehlig <jfehlig@xxxxxxxx>]

If available, let libxl handle reaping any children it creates by
specifying libxl_sigchld_owner_libxl_always_selective_reap.  This
feature was added to improve subprocess handling in libxl when used
in an application that does not install a SIGCHLD handler like
libvirt

http://lists.xen.org/archives/html/xen-devel/2014-01/msg01555.html

Prior to this patch, it is possible to hit asserts in libxl when
reaping subprocesses, particularly during simultaneous operations
on multiple domains.  With this patch, and the corresponding changes
to libxl, I no longer see the asserts.

Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
---

The libxl patch has not yet hit xen.git, but without it this patch
has no semantic change, only explicitly setting chldowner to the
default of libxl_sigchld_owner_libxl.

 src/libxl/libxl_domain.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
index fbd6cab..eb2e50e 100644
--- a/src/libxl/libxl_domain.c
+++ b/src/libxl/libxl_domain.c
@@ -358,6 +358,14 @@ virDomainDefParserConfig libxlDomainDefParserConfig = {
     .devicesPostParseCallback = libxlDomainDeviceDefPostParse,
 };
 
+static const libxl_childproc_hooks libxl_child_hooks = {
+#ifdef LIBXL_HAVE_SIGCHLD_OWNER_SELECTIVE_REAP
+    .chldowner = libxl_sigchld_owner_libxl_always_selective_reap,
+#else
+    .chldowner = libxl_sigchld_owner_libxl,
+#endif
+};
+
 int
 libxlDomainObjPrivateInitCtx(virDomainObjPtr vm)
 {
@@ -395,6 +403,7 @@ libxlDomainObjPrivateInitCtx(virDomainObjPtr vm)
     }
 
     libxl_osevent_register_hooks(priv->ctx, &libxl_event_callbacks, priv);
+    libxl_childproc_setmode(priv->ctx, &libxl_child_hooks, priv);
 
     ret = 0;
 
-- 
1.8.1.4


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