linux-kernel - Re: [RFC] Deadlock via recursive wakeup via RCU with threadirqs

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Date:   Mon, 1 Jul 2019 05:23:05 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Scott Wood <swood@...hat.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        rcu <rcu@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [RFC] Deadlock via recursive wakeup via RCU with threadirqs

On Mon, Jul 01, 2019 at 12:24:42PM +0200, Sebastian Andrzej Siewior wrote:
> On 2019-07-01 11:42:15 [+0200], Peter Zijlstra wrote:
> > I'm not sure if smp_send_reschedule() can be used as self-IPI, some
> > hardware doesn't particularly like that IIRC. That is, hardware might
> > only have interfaces to IPI _other_ CPUs, but not self.
> > 
> > The normal scheduler code takes care to not call smp_send_reschedule()
> > to self.
> 
> and irq_work:
>   471ba0e686cb1 ("irq_work: Do not raise an IPI when queueing work on the local CPU")

OK, so it looks like I will need to use something else.  But thank you
for calling my attention to this commit.

							Thanx, Paul