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From: Mark Rutland <mark.rutland@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	mingo@kernel.org, will@kernel.org, boqun.feng@gmail.com,
	tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com,
	x86@kernel.org, hpa@zytor.com, seanjc@google.com,
	pbonzini@redhat.com, jgross@suse.com, srivatsa@csail.mit.edu,
	amakhalov@vmware.com, pv-drivers@vmware.com, mhiramat@kernel.org,
	wanpengli@tencent.com, vkuznets@redhat.com,
	boris.ostrovsky@oracle.com, rafael@kernel.org,
	daniel.lezcano@linaro.org, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
	vschneid@redhat.com, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
	linux-trace-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
Date: Tue, 24 Jan 2023 17:12:14 +0000	[thread overview]
Message-ID: <Y9ARbgtYhxSuOIlZ@FVFF77S0Q05N> (raw)
In-Reply-To: <Y8/u00WHGElMDjoo@hirez.programming.kicks-ass.net>

On Tue, Jan 24, 2023 at 03:44:35PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 23, 2023 at 05:07:53PM -0500, Steven Rostedt wrote:
> 
> > Actually, perhaps we can just add this, and all you need to do is create
> > and set CONFIG_NO_RCU_TRACING (or some other name).
> 
> Elsewhere I've used CONFIG_ARCH_WANTS_NO_INSTR for this.

Yes please; if we use CONFIG_ARCH_WANTS_NO_INSTR then arm64 will get this "for
free" once we add the missing checks (which I assume we need) in our ftrace_prepare_return().

> Anyway, I took it for a spin and it .... doesn't seems to do the job.
> 
> With my patch the first splat is
> 
>   "RCU not on for: cpuidle_poll_time+0x0/0x70"
> 
> While with yours I seems to get the endless:
> 
>   "WARNING: suspicious RCU usage"
> 
> thing. Let me see if I can figure out where it goes side-ways.

Hmmm... for WARN_ONCE() don't we need to wake RCU first also? I thought we
needed that at least for the printk machinery?

Thanks,
Mark.

WARNING: multiple messages have this Message-ID (diff)
From: Mark Rutland <mark.rutland@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: juri.lelli@redhat.com, daniel.lezcano@linaro.org,
	wanpengli@tencent.com, kvm@vger.kernel.org, rafael@kernel.org,
	pv-drivers@vmware.com, dave.hansen@linux.intel.com,
	virtualization@lists.linux-foundation.org, bsegall@google.com,
	amakhalov@vmware.com, will@kernel.org, vschneid@redhat.com,
	hpa@zytor.com, x86@kernel.org, mingo@kernel.org, mgorman@suse.de,
	linux-trace-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	boqun.feng@gmail.com, Steven Rostedt <rostedt@goodmis.org>,
	bp@alien8.de, vincent.guittot@linaro.org,
	boris.ostrovsky@oracle.com, dietmar.eggemann@arm.com,
	jgross@suse.com, seanjc@google.com, linux-kernel@vger.kernel.org,
	tglx@linutronix.de, mhiramat@kernel.org, pbonzini@redhat.com,
	bristot@redhat.com
Subject: Re: [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled
Date: Tue, 24 Jan 2023 17:12:14 +0000	[thread overview]
Message-ID: <Y9ARbgtYhxSuOIlZ@FVFF77S0Q05N> (raw)
In-Reply-To: <Y8/u00WHGElMDjoo@hirez.programming.kicks-ass.net>

On Tue, Jan 24, 2023 at 03:44:35PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 23, 2023 at 05:07:53PM -0500, Steven Rostedt wrote:
> 
> > Actually, perhaps we can just add this, and all you need to do is create
> > and set CONFIG_NO_RCU_TRACING (or some other name).
> 
> Elsewhere I've used CONFIG_ARCH_WANTS_NO_INSTR for this.

Yes please; if we use CONFIG_ARCH_WANTS_NO_INSTR then arm64 will get this "for
free" once we add the missing checks (which I assume we need) in our ftrace_prepare_return().

> Anyway, I took it for a spin and it .... doesn't seems to do the job.
> 
> With my patch the first splat is
> 
>   "RCU not on for: cpuidle_poll_time+0x0/0x70"
> 
> While with yours I seems to get the endless:
> 
>   "WARNING: suspicious RCU usage"
> 
> thing. Let me see if I can figure out where it goes side-ways.

Hmmm... for WARN_ONCE() don't we need to wake RCU first also? I thought we
needed that at least for the printk machinery?

Thanks,
Mark.
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Virtualization@lists.linux-foundation.org
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  reply	other threads:[~2023-01-24 17:12 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-23 20:50 [PATCH 0/6] A few cpuidle vs rcu fixes Peter Zijlstra
2023-01-23 20:50 ` Peter Zijlstra
2023-01-23 20:50 ` [PATCH 1/6] x86: Always inline arch_atomic64 Peter Zijlstra
2023-01-23 20:50   ` Peter Zijlstra
2023-01-23 20:50 ` [PATCH 2/6] x86/pvclock: improve atomic update of last_value in pvclock_clocksource_read Peter Zijlstra
2023-01-23 20:50   ` Peter Zijlstra
2023-01-23 20:50 ` [PATCH 3/6] ftrace/x86: Warn and ignore graph tracing when RCU is disabled Peter Zijlstra
2023-01-23 20:50   ` Peter Zijlstra
2023-01-23 21:53   ` Steven Rostedt
2023-01-23 21:53     ` Steven Rostedt
2023-01-23 22:07     ` Steven Rostedt
2023-01-23 22:07       ` Steven Rostedt
2023-01-24 14:44       ` Peter Zijlstra
2023-01-24 14:44         ` Peter Zijlstra
2023-01-24 17:12         ` Mark Rutland [this message]
2023-01-24 17:12           ` Mark Rutland
2023-01-25  9:37           ` Peter Zijlstra
2023-01-25  9:37             ` Peter Zijlstra
2023-01-25 10:47           ` Peter Zijlstra
2023-01-25 10:47             ` Peter Zijlstra
2023-01-25 11:32             ` Mark Rutland
2023-01-25 11:32               ` Mark Rutland
2023-01-25 18:46             ` Paul E. McKenney
2023-01-26  9:28               ` Peter Zijlstra
2023-01-26  9:28                 ` Peter Zijlstra
2023-01-28 19:12                 ` Paul E. McKenney
2023-01-23 20:50 ` [PATCH 4/6] x86: Mark sched_clock() noinstr Peter Zijlstra
2023-01-23 20:50   ` Peter Zijlstra
2023-01-23 20:50 ` [PATCH 5/6] sched/clock: Make local_clock() noinstr Peter Zijlstra
2023-01-23 20:50   ` Peter Zijlstra
2023-01-23 20:50 ` [PATCH 6/6] cpuidle: Fix poll_idle() noinstr annotation Peter Zijlstra
2023-01-23 20:50   ` Peter Zijlstra
2023-01-24 14:24   ` Rafael J. Wysocki
2023-01-24 14:24     ` Rafael J. Wysocki
2023-01-24 16:34 ` [PATCH 0/6] A few cpuidle vs rcu fixes Mark Rutland
2023-01-24 16:34   ` Mark Rutland
2023-01-24 17:30   ` Mark Rutland
2023-01-24 17:30     ` Mark Rutland
2023-01-24 18:39     ` Mark Rutland
2023-01-24 18:39       ` Mark Rutland
2023-01-25  9:35       ` Peter Zijlstra
2023-01-25  9:35         ` Peter Zijlstra
2023-01-25  9:40         ` Peter Zijlstra
2023-01-25  9:40           ` Peter Zijlstra
2023-01-25 10:23           ` Mark Rutland
2023-01-25 10:23             ` Mark Rutland
2023-01-31 14:22           ` [tip: sched/core] cpuidle: tracing, preempt: Squash _rcuidle tracing tip-bot2 for Peter Zijlstra
2023-01-25  9:31   ` [PATCH 0/6] A few cpuidle vs rcu fixes Peter Zijlstra
2023-01-25  9:31     ` Peter Zijlstra
2023-01-25  9:36     ` Mark Rutland
2023-01-25  9:36       ` Mark Rutland
2023-01-25 15:20 ` Mark Rutland
2023-01-25 15:20   ` Mark Rutland

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