linux-kernel - Re: [RFC][PATCH 17/22] sched: add signaling overrunning -deadline tasks.

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Date:	Fri, 12 Nov 2010 17:04:46 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Raistlin <raistlin@...ux.it>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chris Friesen <cfriesen@...tel.com>, oleg@...hat.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	Darren Hart <darren@...art.com>,
	Johan Eker <johan.eker@...csson.com>,
	"p.faure" <p.faure@...tech.ch>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Claudio Scordino <claudio@...dence.eu.com>,
	michael trimarchi <trimarchi@...is.sssup.it>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	Tommaso Cucinotta <cucinotta@...up.it>,
	Juri Lelli <juri.lelli@...il.com>,
	Nicola Manica <nicola.manica@...i.unitn.it>,
	Luca Abeni <luca.abeni@...tn.it>,
	Dhaval Giani <dhaval@...is.sssup.it>,
	Harald Gustafsson <hgu1972@...il.com>,
	paulmck <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 17/22] sched: add signaling overrunning -deadline
 tasks.

On Fri, 2010-11-12 at 16:39 +0100, Raistlin wrote:
> On Thu, 2010-11-11 at 22:58 +0100, Peter Zijlstra wrote:
> > On Fri, 2010-10-29 at 08:40 +0200, Raistlin wrote:
> > > +static inline void __dl_signal(struct task_struct *tsk, int which)
> > > +{
> > > +       struct siginfo info;
> > > +       long long amount = which == SF_SIG_DMISS ? tsk->dl.stats.last_dmiss :
> > > +                          tsk->dl.stats.last_rorun;
> > > +
> > > +       info.si_signo = SIGXCPU;
> > > +       info.si_errno = which;
> > > +       info.si_code = SI_KERNEL;
> > > +       info.si_pid = 0;
> > > +       info.si_uid = 0;
> > > +       info.si_value.sival_int = (int)amount;
> > > +
> > > +       /* Correctly take the locks on task's sighand */
> > > +       __group_send_sig_info(SIGXCPU, &info, tsk);
> > > +       /* Log what happened to dmesg */
> > > +       printk(KERN_INFO "SCHED_DEADLINE: 0x%4x by %Ld [ns] in %d (%s)\n",
> > > +              which, amount, task_pid_nr(tsk), tsk->comm);
> > > +} 
> > 
> > This being a G-EDF like scheduler with a u<=1 schedulability test, we're
> > firmly in soft-rt territory which means the above will be very easy to
> > trigger.. Maybe not spam dmesg?
> >
> Ok, right. Maybe, if I add the SF_HARD_RT flag (and force the hard tasks
> to run on a single CPU they must specify) I can keep the notification
> for those tasks only. What do you think?

Sure.. that makes sense.
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