Re: [Xen-devel] [PATCH 3 of 3] remus: handle exceptions while installing/unstalling net buffer

[Shriram Rajagopalan <rshriram@xxxxxxxxx>]

On Wed, Jun 22, 2011 at 9:37 AM, Shriram Rajagopalan <rshriram@xxxxxxxxx> wrote:

# HG changeset patch
# User Shriram Rajagopalan <rshriram@xxxxxxxxx>
# Date 1308749695 25200
# Node ID 9eed27800ff6a2e6d73f138f20af072c1b41925e
# Parent  794ead1a2be0578d70c38f006e7ab61c7abe9203
remus: handle exceptions while installing/unstalling net buffer

Signed-off-by: Shriram Rajagopalan <rshriram@xxxxxxxxx>

diff -r 794ead1a2be0 -r 9eed27800ff6 tools/python/xen/remus/device.py
--- a/tools/python/xen/remus/device.py  Tue Jun 21 12:11:44 2011 -0700
+++ b/tools/python/xen/remus/device.py  Wed Jun 22 06:34:55 2011 -0700
@@ -169,15 +169,25 @@
        self.vif = vif
        # voodoo from http://www.linuxfoundation.org/collaborate/workgroups/networking/ifb#Typical_Usage
        util.runcmd('ip link set %s up' % self.devname)
-        util.runcmd('tc qdisc add dev %s ingress' % vif.dev)
+        try:
+            util.runcmd('tc qdisc add dev %s ingress' % vif.dev)
+        except util.PipeException, e:
+            # check if error indicates that ingress qdisc
+            # already exists on the vif. If so, ignore it.
+            ignoreme = 'RTNETLINK answers: File exists'
+            if ignoreme in str(e):
+                pass
+            else:
+                raise e
        util.runcmd('tc filter add dev %s parent ffff: proto ip pref 10 '
                    'u32 match u32 0 0 action mirred egress redirect '
                    'dev %s' % (vif.dev, self.devname))

    def uninstall(self):
-        util.runcmd('tc filter del dev %s parent ffff: proto ip pref 10 u32' \
-                        % self.vif.dev)
-        util.runcmd('tc qdisc del dev %s ingress' % self.vif.dev)
+        try:
+            util.runcmd('tc qdisc del dev %s ingress' % self.vif.dev)
+        except util.PipeException, e:
+            pass
        util.runcmd('ip link set %s down' % self.devname)

 class IMQBuffer(Netbuf):
@@ -373,9 +383,15 @@

    def uninstall(self):
        if self.installed:
-            req = qdisc.delrequest(self.bufdevno, self.handle)
-            self.rth.talk(req.pack())
+            try:
+                req = qdisc.delrequest(self.bufdevno, self.handle)
+                self.rth.talk(req.pack())
+            except IOError, e:
+                pass
            self.installed = False

-        self.bufdev.uninstall()
-        self.pool.put(self.bufdev)
+            try:
+                self.bufdev.uninstall()
+            except util.PipeException, e:
+                pass
+            self.pool.put(self.bufdev)
diff -r 794ead1a2be0 -r 9eed27800ff6 tools/python/xen/remus/util.py
--- a/tools/python/xen/remus/util.py    Tue Jun 21 12:11:44 2011 -0700
+++ b/tools/python/xen/remus/util.py    Wed Jun 22 06:34:55 2011 -0700
@@ -65,8 +65,10 @@
        proc.wait()
        if proc.returncode:
            print ' '.join(args)
-            print stderr.strip()
-            raise PipeException('%s failed' % args[0], proc.returncode)
+            errmsg = stderr.strip()
+            print errmsg
+            raise PipeException('%s failed (errmsg: %s)' % (args[0], errmsg),
+                                proc.returncode)
        return stdout
    except (OSError, IOError), inst:
        raise PipeException('could not run %s' % args[0], inst.errno)

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As Brendan pointed out, 90% of what I proposed to remove
in patches 1 & 2 of this series might be useful for folks who want to hack on Remus
or live migration code. I ll do the clean up later, more carefully.

Ian, if you have no objection to this patch, could you take in this one alone and
reject patches 1 & 2? Or do you want me to send this one separately again?

shriram
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