[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 15/36] cpuidle,cpu_pm: Remove RCU fiddling from cpu_pm_{enter,exit}()
- To: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- From: Mark Rutland <mark.rutland@xxxxxxx>
- Date: Tue, 14 Jun 2022 17:53:25 +0100
- Cc: rth@xxxxxxxxxxx, ink@xxxxxxxxxxxxxxxxxxxx, mattst88@xxxxxxxxx, vgupta@xxxxxxxxxx, linux@xxxxxxxxxxxxxxx, ulli.kroll@xxxxxxxxxxxxxx, linus.walleij@xxxxxxxxxx, shawnguo@xxxxxxxxxx, Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>, kernel@xxxxxxxxxxxxxx, festevam@xxxxxxxxx, linux-imx@xxxxxxx, tony@xxxxxxxxxxx, khilman@xxxxxxxxxx, catalin.marinas@xxxxxxx, will@xxxxxxxxxx, guoren@xxxxxxxxxx, bcain@xxxxxxxxxxx, chenhuacai@xxxxxxxxxx, kernel@xxxxxxxxxx, geert@xxxxxxxxxxxxxx, sammy@xxxxxxxxx, monstr@xxxxxxxxx, tsbogend@xxxxxxxxxxxxxxxx, dinguyen@xxxxxxxxxx, jonas@xxxxxxxxxxxx, stefan.kristiansson@xxxxxxxxxxxxx, shorne@xxxxxxxxx, James.Bottomley@xxxxxxxxxxxxxxxxxxxxx, deller@xxxxxx, mpe@xxxxxxxxxxxxxx, benh@xxxxxxxxxxxxxxxxxxx, paulus@xxxxxxxxx, paul.walmsley@xxxxxxxxxx, palmer@xxxxxxxxxxx, aou@xxxxxxxxxxxxxxxxx, hca@xxxxxxxxxxxxx, gor@xxxxxxxxxxxxx, agordeev@xxxxxxxxxxxxx, borntraeger@xxxxxxxxxxxxx, svens@xxxxxxxxxxxxx, ysato@xxxxxxxxxxxxxxxxxxxx, dalias@xxxxxxxx, davem@xxxxxxxxxxxxx, richard@xxxxxx, anton.ivanov@xxxxxxxxxxxxxxxxxx, johannes@xxxxxxxxxxxxxxxx, tglx@xxxxxxxxxxxxx, mingo@xxxxxxxxxx, bp@xxxxxxxxx, dave.hansen@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, hpa@xxxxxxxxx, acme@xxxxxxxxxx, alexander.shishkin@xxxxxxxxxxxxxxx, jolsa@xxxxxxxxxx, namhyung@xxxxxxxxxx, jgross@xxxxxxxx, srivatsa@xxxxxxxxxxxxx, amakhalov@xxxxxxxxxx, pv-drivers@xxxxxxxxxx, boris.ostrovsky@xxxxxxxxxx, chris@xxxxxxxxxx, jcmvbkbc@xxxxxxxxx, rafael@xxxxxxxxxx, lenb@xxxxxxxxxx, pavel@xxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, mturquette@xxxxxxxxxxxx, sboyd@xxxxxxxxxx, daniel.lezcano@xxxxxxxxxx, lpieralisi@xxxxxxxxxx, sudeep.holla@xxxxxxx, agross@xxxxxxxxxx, bjorn.andersson@xxxxxxxxxx, anup@xxxxxxxxxxxxxx, thierry.reding@xxxxxxxxx, jonathanh@xxxxxxxxxx, jacob.jun.pan@xxxxxxxxxxxxxxx, Arnd Bergmann <arnd@xxxxxxxx>, yury.norov@xxxxxxxxx, andriy.shevchenko@xxxxxxxxxxxxxxx, linux@xxxxxxxxxxxxxxxxxx, rostedt@xxxxxxxxxxx, pmladek@xxxxxxxx, senozhatsky@xxxxxxxxxxxx, john.ogness@xxxxxxxxxxxxx, paulmck@xxxxxxxxxx, frederic@xxxxxxxxxx, quic_neeraju@xxxxxxxxxxx, josh@xxxxxxxxxxxxxxxx, mathieu.desnoyers@xxxxxxxxxxxx, jiangshanlai@xxxxxxxxx, joel@xxxxxxxxxxxxxxxxx, juri.lelli@xxxxxxxxxx, vincent.guittot@xxxxxxxxxx, dietmar.eggemann@xxxxxxx, bsegall@xxxxxxxxxx, mgorman@xxxxxxx, bristot@xxxxxxxxxx, vschneid@xxxxxxxxxx, jpoimboe@xxxxxxxxxx, linux-alpha@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-snps-arc@xxxxxxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-omap@xxxxxxxxxxxxxxx, linux-csky@xxxxxxxxxxxxxxx, linux-hexagon@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-m68k@xxxxxxxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxxx, openrisc@xxxxxxxxxxxxxxxxxxxx, linux-parisc@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, linux-riscv@xxxxxxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, linux-um@xxxxxxxxxxxxxxxxxxx, linux-perf-users@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-xtensa@xxxxxxxxxxxxxxxx, linux-acpi@xxxxxxxxxxxxxxx, linux-pm@xxxxxxxxxxxxxxx, linux-clk@xxxxxxxxxxxxxxx, linux-arm-msm@xxxxxxxxxxxxxxx, linux-tegra@xxxxxxxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, rcu@xxxxxxxxxxxxxxx
- Delivery-date: Wed, 15 Jun 2022 04:05:42 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Tue, Jun 14, 2022 at 06:42:14PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 14, 2022 at 05:13:16PM +0100, Mark Rutland wrote:
> > On Wed, Jun 08, 2022 at 04:27:38PM +0200, Peter Zijlstra wrote:
> > > All callers should still have RCU enabled.
> >
> > IIUC with that true we should be able to drop the RCU_NONIDLE() from
> > drivers/perf/arm_pmu.c, as we only needed that for an invocation via a pm
> > notifier.
> >
> > I should be able to give that a spin on some hardware.
> >
> > >
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> > > ---
> > > kernel/cpu_pm.c | 9 ---------
> > > 1 file changed, 9 deletions(-)
> > >
> > > --- a/kernel/cpu_pm.c
> > > +++ b/kernel/cpu_pm.c
> > > @@ -30,16 +30,9 @@ static int cpu_pm_notify(enum cpu_pm_eve
> > > {
> > > int ret;
> > >
> > > - /*
> > > - * This introduces a RCU read critical section, which could be
> > > - * disfunctional in cpu idle. Copy RCU_NONIDLE code to let RCU know
> > > - * this.
> > > - */
> > > - rcu_irq_enter_irqson();
> > > rcu_read_lock();
> > > ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL);
> > > rcu_read_unlock();
> > > - rcu_irq_exit_irqson();
> >
> > To make this easier to debug, is it worth adding an assertion that RCU is
> > watching here? e.g.
> >
> > RCU_LOCKDEP_WARN(!rcu_is_watching(),
> > "cpu_pm_notify() used illegally from EQS");
> >
>
> My understanding is that rcu_read_lock() implies something along those
> lines when PROVE_RCU.
Ah, duh. Given that:
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Mark.
|