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From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	mingo@kernel.org, joel@joelfernandes.org,
	gregkh@linuxfoundation.org, gustavo@embeddedor.com,
	tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org,
	mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com
Subject: Re: [PATCH 4/8] sched,rcu,tracing: Mark preempt_count_{add,sub}() notrace
Date: Wed, 12 Feb 2020 10:14:15 -0500	[thread overview]
Message-ID: <20200212101415.3615d66c@gandalf.local.home> (raw)
In-Reply-To: <20200212150211.GS14897@hirez.programming.kicks-ass.net>

On Wed, 12 Feb 2020 16:02:11 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, Feb 12, 2020 at 09:24:17AM -0500, Steven Rostedt wrote:
> > On Wed, 12 Feb 2020 10:32:14 +0100
> > Peter Zijlstra <peterz@infradead.org> wrote:
> >   
> > > Because of the requirement that no tracing happens until after we've
> > > incremented preempt_count, see nmi_enter() / trace_rcu_enter(), mark
> > > these functions as notrace.  
> > 
> > I actually depend on these function being traced.  
> 
> Why? They already have a tracepoint inside.

Only when enabled.

> 
> > We do have
> > "preempt_enable_notrace()" and "preempt_disable_notrace()" for places
> > that shouldn't be traced. Can't we use those? (or simply
> > __preempt_count_add()) in the nmi_enter() code instead? (perhaps create
> > a preempt_count_add_notrace()).  
> 
> My initial patch has __preempt_count_add/sub() in, but then I figured
> someone would go complain the tracepoint would go missing.

Fine, but what bug are you trying to fix? I haven't seen one mentioned
yet. Function tracing has recursion protection, and tracing
preempt_count in nmi_enter() causes no problems. What's the problem you
are trying to solve?

-- Steve

  reply	other threads:[~2020-02-12 15:14 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12  9:32 [PATCH 0/8] tracing vs rcu vs nmi Peter Zijlstra
2020-02-12  9:32 ` [PATCH 1/8] rcu: Rename rcu_irq_{enter,exit}_irqson() Peter Zijlstra
2020-02-12  9:32 ` [PATCH 2/8] rcu: Mark rcu_dynticks_curr_cpu_in_eqs() inline Peter Zijlstra
2020-02-12  9:32 ` [PATCH 3/8] rcu,tracing: Create trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-12  9:32 ` [PATCH 4/8] sched,rcu,tracing: Mark preempt_count_{add,sub}() notrace Peter Zijlstra
2020-02-12 14:24   ` Steven Rostedt
2020-02-12 15:02     ` Peter Zijlstra
2020-02-12 15:14       ` Steven Rostedt [this message]
2020-02-12 15:38         ` Peter Zijlstra
2020-02-12  9:32 ` [PATCH 5/8] x86,tracing: Mark debug_stack_{set_zero,reset)() notrace Peter Zijlstra
2020-02-12 14:25   ` Steven Rostedt
2020-02-12 15:04     ` Peter Zijlstra
2020-02-12 15:18       ` Steven Rostedt
2020-02-12 15:39         ` Peter Zijlstra
2020-02-12  9:32 ` [PATCH 6/8] perf,tracing: Prepare the perf-trace interface for RCU changes Peter Zijlstra
2020-02-12 14:26   ` Steven Rostedt
2020-02-12 15:07     ` Mathieu Desnoyers
2020-02-12  9:32 ` [PATCH 7/8] tracing: Employ trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-12  9:32 ` [PATCH 8/8] tracing: Remove regular RCU context for _rcuidle tracepoints (again) Peter Zijlstra
2020-02-12 14:29   ` Steven Rostedt
2020-02-12 15:12     ` Peter Zijlstra
2020-02-12 10:01 ` [PATCH 0/8] tracing vs rcu vs nmi Peter Zijlstra
2020-02-12 10:56   ` Will Deacon
2020-02-12 11:58     ` Peter Zijlstra
2020-02-12 14:32     ` Steven Rostedt
2020-02-12 15:21       ` Peter Zijlstra
2020-02-12 10:03 ` Peter Zijlstra
2020-02-12 10:07 ` Peter Zijlstra
2020-02-12 10:09 ` Peter Zijlstra

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