On Wed, 2016-04-20 at 17:18 +0200, Jakub Hrozek wrote:
On Wed, Apr 20, 2016 at 09:43:05AM -0400, Simo Sorce wrote:
> On Wed, 2016-04-20 at 11:12 +0200, Jakub Hrozek wrote:
> > On Wed, Apr 20, 2016 at 10:32:59AM +0200, Jakub Hrozek wrote:
> > > > > From 0dff46755af6063ed4b0339020ae5bb686692de1 Mon Sep 17
> > > > > From: Simo Sorce <simo(a)redhat.com>
> > > > > Date: Tue, 12 Jan 2016 20:13:28 -0500
> > > > > Subject: [PATCH 02/15] Server: Enable Watchdog in all daemons
> > > > >
> > > > > This allows the services to self monitor.
> > > > >
> > > > > Related:
> > > > > https://fedorahosted.org/sssd/ticket/2921
> > > >
> > > > Is it intentional that we also enable the watchdog in monitor? I
> > > > seen the sssd process being stuck and if it does, we probably have
> > > > bigger issues, so it's probably fine, I just need to remember to
> > > > SIGSTOP sssd when testing anymore :)
> > > >
> > > > Otherwise ack.
> > >
> > > Actually, more questions...
> > >
> > > Can you help me test this patch? I tried to inject sleep() into sssd_be
> > > code and the sleep was just interrupted by the SIGRT delivery. With SSSD,
> > > most of the time the process was stuck was because it was writing a lot
> > > data with fsync()/fdatasync(). I can't find any information in the
> > > fsync manpage on how fsync behaves wrt signals. openpub manpages indicate
> > > that fsync would return EINTR, which worries me a bit..
> > Hmm, sorry, I was not being careful enough. man 7 signal also says:
> > """
> > The sleep(3) function is also never restarted if interrupted by a
> > handler, but gives a success return: the number of seconds remaining to
> > sleep.
> > """
> > so the sleep testcase was wrong even though CatchSignal uses SA_RESTART.
> > But do you know how would write() or fsync() behave here? The signal
> > manpage is a bit unclar to me as it talks about "slow" devices..
> > Or can you think of some easy way to test this?
> The fsync manpage here says:
> "The call blocks until the device reports that the transfer has
> And does not report EINTR as a possible error.
> That said I am a bit unclear what you want to test actually ?
I want to actually test that the service can be restarted if stuck and
reconnects fine. So far I haven't been lucky - SIGSTOP-ing the service
stopped delivery of the signals, so did attaching gdb and waiting.
gdb it, do *not* cont, but tell gdb to not block signals, iirc you do
that with: handle SIGRTMIN nostop noprint pass
if you then wait in gdb the timers will fire and eventually the process
will be killed because you are blocking the main loop and not resetting
But most importantly I want to make sure that if tdb is writing a
transaction and the signal is delivered, then we don't fsync() in tdb
doesn't get interrupted and doesn't corrupt the database. From all the
cases where users complained about a service being restarted, it was
always about tdb writing stuff to disk...
I'm inquiring about this.
Simo Sorce * Red Hat, Inc * New York