From: Greg Kurz <groug@kaod.org>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
qemu-stable@nongnu.org, qemu-devel@nongnu.org,
Eduardo Habkost <ehabkost@redhat.com>
Subject: Re: [PATCH v3 2/2] accel/tcg: Register a force_rcu notifier
Date: Tue, 9 Nov 2021 18:24:07 +0100 [thread overview]
Message-ID: <20211109182407.75f623f8@bahia> (raw)
In-Reply-To: <8a184041-39ad-1207-f32b-673e2b8da0f2@linaro.org>
On Tue, 9 Nov 2021 09:21:27 +0100
Richard Henderson <richard.henderson@linaro.org> wrote:
> On 11/9/21 8:54 AM, Richard Henderson wrote:
> > On 11/8/21 12:33 PM, Greg Kurz wrote:
> >> +static void rr_force_rcu(Notifier *notify, void *data)
> >> +{
> >> + /*
> >> + * Called with rcu_registry_lock held, using async_run_on_cpu() ensures
> >> + * that there are no deadlocks.
> >> + */
> >> + async_run_on_cpu(first_cpu, do_nothing, RUN_ON_CPU_NULL);
> >> +}
> >
> > Should first_cpu really be rr_current_cpu?
> > It's not clear to me that this will work for -smp 2 -cpu thread=single.
>
Why wouldn't it work ? IIUC we always have a first_cpu and
async_run_on_cpu() will kick any vCPU currently run by the
RR thread... or am I missing something ?
Anyway, it seems more explicit to use rr_current_cpu.
> Alternately, no async_run_on_cpu at all, just rr_kick_next_cpu().
>
Heh, this looks even better ! I'll try this right away.
Thanks Richard !
--
Greg
>
> r~
>
next prev parent reply other threads:[~2021-11-09 17:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-08 11:33 [PATCH v3 0/2] accel/tcg: Fix monitor deadlock Greg Kurz
2021-11-08 11:33 ` [PATCH v3 1/2] rcu: Introduce force_rcu notifier Greg Kurz
2021-11-08 11:33 ` [PATCH v3 2/2] accel/tcg: Register a " Greg Kurz
2021-11-09 7:54 ` Richard Henderson
2021-11-09 8:21 ` Richard Henderson
2021-11-09 17:24 ` Greg Kurz [this message]
2021-11-09 18:03 ` Paolo Bonzini
2021-11-09 18:29 ` Greg Kurz
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