linux-kernel - Re: [RFC PATCH 6/9] livepatch: create per-task consistency model

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Message-ID: <20150210145904.GC21643@treble.redhat.com>
Date:	Tue, 10 Feb 2015 08:59:04 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Seth Jennings <sjenning@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
	Vojtech Pavlik <vojtech@...e.cz>,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 6/9] livepatch: create per-task consistency model

On Tue, Feb 10, 2015 at 07:58:30PM +0900, Masami Hiramatsu wrote:
> (2015/02/10 2:31), Josh Poimboeuf wrote:
> > +/*
> > + * Try to safely transition a task to the universe goal.  If the task is
> > + * currently running or is sleeping on a to-be-patched or to-be-unpatched
> > + * function, return false.
> > + */
> > +static bool klp_transition_task(struct task_struct *t)
> > +{
> > +	struct rq *rq;
> > +	unsigned long flags;
> > +	int ret;
> > +	bool success = false;
> > +
> > +	if (t->klp_universe == klp_universe_goal)
> > +		return true;
> > +
> > +	rq = task_rq_lock(t, &flags);
> > +
> > +	if (task_running(rq, t) && t != current) {
> > +		pr_debug("%s: pid %d (%s) is running\n", __func__, t->pid,
> > +			 t->comm);
> > +		goto done;
> > +	}
> 
> Let me confirm that this always skips running tasks, and klp retries
> checking by using delayed worker, correct?

Correct.  Also, patch 9 of the series adds other ways to convert tasks,
using syscalls, irqs and signals.


-- 
Josh
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