All of lore.kernel.org
 help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Joel Fernandes <joel@joelfernandes.org>,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	rostedt@goodmis.org, mingo@kernel.org,
	gregkh@linuxfoundation.org, gustavo@embeddedor.com,
	tglx@linutronix.de, josh@joshtriplett.org,
	mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com
Subject: Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}()
Date: Thu, 13 Feb 2020 17:40:31 +0100	[thread overview]
Message-ID: <20200213164031.GH14914@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200213135138.GB2935@paulmck-ThinkPad-P72>

On Thu, Feb 13, 2020 at 05:51:38AM -0800, Paul E. McKenney wrote:

> The reason for the irq argument is to avoid invoking
> rcu_prepare_for_idle() and rcu_dynticks_task_enter() from NMI context
> from rcu_nmi_exit_common().  Similarly, we need to avoid invoking
> rcu_dynticks_task_exit() and rcu_cleanup_after_idle() from NMI context
> from rcu_nmi_enter_common().

Aaah, I see. I didn't grep hard enough earlier today (I only found
stubs). Yes, those take locks, we mustn't call them from NMI context.

> It might well be that I could make these functions be NMI-safe, but
> rcu_prepare_for_idle() in particular would be a bit ugly at best.
> So, before looking into that, I have a question.  Given these proposed
> changes, will rcu_nmi_exit_common() and rcu_nmi_enter_common() be able
> to just use in_nmi()?

That _should_ already be the case today. That is, if we end up in a
tracer and in_nmi() is unreliable we're already screwed anyway.

  reply	other threads:[~2020-02-13 16:40 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12 21:01 [PATCH v2 0/9] tracing vs rcu vs nmi Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 1/9] rcu: Rename rcu_irq_{enter,exit}_irqson() Peter Zijlstra
2020-02-12 22:38   ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 2/9] rcu: Mark rcu_dynticks_curr_cpu_in_eqs() inline Peter Zijlstra
2020-02-12 22:38   ` Joel Fernandes
2020-02-13  1:41     ` Steven Rostedt
2020-02-13 14:25       ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-12 23:20   ` Joel Fernandes
2020-02-13  8:27     ` Peter Zijlstra
2020-02-13 13:31       ` Joel Fernandes
2020-02-13 13:51       ` Paul E. McKenney
2020-02-13 16:40         ` Peter Zijlstra [this message]
2020-02-13 18:56           ` Paul E. McKenney
2020-02-13 20:44             ` Joel Fernandes
2020-02-13 20:54               ` Paul E. McKenney
2020-02-13 21:19                 ` Joel Fernandes
2020-02-13 21:38                   ` Steven Rostedt
2020-02-13 21:50                     ` Paul E. McKenney
2020-02-13 22:04                       ` Steven Rostedt
2020-02-13 22:39                         ` Paul E. McKenney
2020-02-14  6:19                           ` Masami Hiramatsu
2020-02-15 14:59                             ` Paul E. McKenney
2020-02-17  8:55                               ` Masami Hiramatsu
2020-02-17 16:31                                 ` Paul E. McKenney
2020-02-18  4:33                                   ` Masami Hiramatsu
2020-02-18 16:12                                     ` Paul E. McKenney
2020-02-18 16:15                                       ` Mathieu Desnoyers
2020-02-18 16:35                                       ` Steven Rostedt
2020-02-18 17:46                                     ` Steven Rostedt
2020-02-18 20:18                                       ` Paul E. McKenney
2020-02-19  2:45                                         ` Masami Hiramatsu
2020-03-06 18:01                                           ` Masami Hiramatsu
2020-03-06 18:47                                             ` Joel Fernandes
2020-03-06 19:11                                             ` Joel Fernandes
2020-03-07  1:58                                               ` Masami Hiramatsu
2020-03-06  0:42                     ` Thomas Gleixner
2020-02-13 21:48                   ` Paul E. McKenney
2020-02-13 22:58                     ` Joel Fernandes
2020-02-13 23:55                       ` Steven Rostedt
2020-02-18 19:58               ` Peter Zijlstra
2020-02-18 20:17                 ` Paul E. McKenney
2020-02-18 20:40                   ` Peter Zijlstra
2020-02-18 21:39                     ` Paul E. McKenney
2020-02-19  9:57                       ` Peter Zijlstra
2020-02-19 12:46                         ` Paul E. McKenney
2020-02-12 23:27   ` Joel Fernandes
2020-02-13  8:28     ` Peter Zijlstra
2020-02-13 18:39       ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 4/9] sched,rcu,tracing: Avoid tracing before in_nmi() is correct Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 5/9] x86,tracing: Add comments to do_nmi() Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 6/9] perf,tracing: Prepare the perf-trace interface for RCU changes Peter Zijlstra
2020-02-12 23:28   ` Joel Fernandes
2020-02-13  8:29     ` Peter Zijlstra
2020-02-13 18:38       ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 7/9] tracing: Employ trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 8/9] tracing: Remove regular RCU context for _rcuidle tracepoints (again) Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 9/9] perf,tracing: Allow function tracing when !RCU Peter Zijlstra
2020-02-14  2:28   ` Sergey Senozhatsky
2020-02-14  2:42     ` Sergey Senozhatsky
2020-02-14  3:32       ` Steven Rostedt
2020-02-14 20:38   ` Kim Phillips
2020-02-14 22:48     ` Steven Rostedt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200213164031.GH14914@hirez.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=gustavo@embeddedor.com \
    --cc=jiangshanlai@gmail.com \
    --cc=joel@joelfernandes.org \
    --cc=josh@joshtriplett.org \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mathieu.desnoyers@efficios.com \
    --cc=mingo@kernel.org \
    --cc=paulmck@kernel.org \
    --cc=rostedt@goodmis.org \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.