[PATCH] libxl: Call setsid(2) before exec'ing device model

[PATCH] libxl: Call setsid(2) before exec'ing device model

[Jim Fehlig]

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While developing libvirt libxl driver I noticed that terminating the
client causes any qemu-dm processes indirectly started by the client to
also terminate.  Calling setsid(2) before exec'ing qemu-dm resolves the
issue but I'm not quite sure about the placement of the setsid() call or
any unforeseen side-affects of its use.  Comments welcome.

Regards,
Jim


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# HG changeset patch
# User Jim Fehlig <jfehlig@novell.com>
# Date 1299552244 25200
# Node ID 94fde77241912b634b492979ffc8cdb9516d6136
# Parent  d8a65dd15d703ba302b0141e9ffe447ff1cd2a64
Call setsid(2) before exec'ing device model

While doing development on libvirt libxenlight driver I noticed
that terminating a libxenlight client causes any qemu-dm
processes that were indirectly created by the client to also
terminate.  Calling setsid(2) before exec'ing qemu-dm resolves
the issue.

    Signed-off-by: Jim Fehlig <jfehlig@novell.com>

diff -r d8a65dd15d70 -r 94fde7724191 tools/libxl/libxl_dm.c
--- a/tools/libxl/libxl_dm.c	Thu Feb 17 11:21:47 2011 -0700
+++ b/tools/libxl/libxl_dm.c	Mon Mar 07 19:44:04 2011 -0700
@@ -681,6 +681,7 @@
     if (rc < 0)
         goto out_close;
     if (!rc) { /* inner child */
+        setsid();
         libxl__exec(null, logfile_w, logfile_w,
                    libxl__abs_path(&gc, info->device_model, libxl_libexec_path()),
                    args);

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Re: [PATCH] libxl: Call setsid(2) before exec'ing device model

[Ian Jackson]

Jim Fehlig writes ("[Xen-devel] [PATCH] libxl: Call setsid(2) before exec'ing device model"):
> While developing libvirt libxl driver I noticed that terminating the
> client causes any qemu-dm processes indirectly started by the client to
> also terminate.  Calling setsid(2) before exec'ing qemu-dm resolves the
> issue but I'm not quite sure about the placement of the setsid() call or
> any unforeseen side-affects of its use.  Comments welcome.

Thanks, I think your patch is correct, and has the setsid in the right
place.  libxl_spawn_spawn was another possibility but I think it's
probably better to do it in the caller.

Applied (with my and Stefano's ack) to 4.1 and unstable.

Ian.