linux-kernel - Re: Endless soft-lockups for compiling workload since next-20200519

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Message-ID: <20200521101047.GH325280@hirez.programming.kicks-ass.net>
Date:   Thu, 21 May 2020 12:10:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     Qian Cai <cai@....pw>, "Paul E. McKenney" <paulmck@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: Endless soft-lockups for compiling workload since next-20200519

On Thu, May 21, 2020 at 02:40:36AM +0200, Frederic Weisbecker wrote:

>                                                        atomic_fetch_or(...., nohz_flags(0))
>     softirq() {                                        #VMEXIT or anything that could stop a CPU for a while
>         run_rebalance_domain() {
>             nohz_idle_balance() {
>                 atomic_andnot(NOHZ_KICK_MASK, nohz_flag(0))

I'm an idiot and didn't have enough wake-up-juice; I missed that andnot
clearing the flag again.

Yes, fun fun fun..