Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 21 May 2020 12:10:47 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Frederic Weisbecker <frederic@kernel.org>
Cc:     Qian Cai <cai@lca.pw>, "Paul E. McKenney" <paulmck@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Borislav Petkov <bp@alien8.de>
Subject: Re: Endless soft-lockups for compiling workload since next-20200519
Message-ID: <20200521101047.GH325280@hirez.programming.kicks-ass.net>
References: <CAG=TAF6jUsQrW-fjbS3vpjkMfn8=MUDsuQxjk3NMfvQa250RHA@mail.gmail.com>
 <20200520125056.GC325280@hirez.programming.kicks-ass.net>
 <20200521004035.GA15455@lenoir>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200521004035.GA15455@lenoir>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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..