linux-kernel - Re: Warning from swake_up_all in 4.14.15-rt13 non-RT

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Message-ID: <20180312142933.GF4043@hirez.programming.kicks-ass.net>
Date:   Mon, 12 Mar 2018 15:29:33 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Corey Minyard <cminyard@...sta.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Tejun Heo <tj@...nel.org>
Subject: Re: Warning from swake_up_all in 4.14.15-rt13 non-RT

On Mon, Mar 12, 2018 at 03:11:07PM +0100, Sebastian Andrzej Siewior wrote:
> I assumed you complained about the unbounded list-walk with interrupts
> disabled (which is cheap but unbound is unbound). So here I suggested I
> move 20 entries off that list a time and enable interrupts again so an
> interrupt could set need_resched.
> But if we get invoked !preemptible then nothing changes.

Right, so any !preemptible invocation of wake_all is bad.