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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH 1/3] tracepoints: Do not use call_rcu_sched() before early_initcall()
Date: Sun, 14 Dec 2014 17:29:28 +0000 (UTC)
Message-ID: <759389895.27358.1418578168225.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20141214122136.1664e104@gandalf.local.home>

----- Original Message -----
> From: "Steven Rostedt" <rostedt@goodmis.org>
> To: "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>
> Cc: linux-kernel@vger.kernel.org, "Linus Torvalds" <torvalds@linux-foundation.org>, "Ingo Molnar" <mingo@kernel.org>,
> "Andrew Morton" <akpm@linux-foundation.org>, "Thomas Gleixner" <tglx@linutronix.de>, "Paul E. McKenney"
> <paulmck@linux.vnet.ibm.com>
> Sent: Sunday, December 14, 2014 12:21:36 PM
> Subject: Re: [PATCH 1/3] tracepoints: Do not use call_rcu_sched() before early_initcall()
> 
> On Sun, 14 Dec 2014 12:14:57 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > If IRQ setup, or other core pieces of code can use this, then I would
> > agree that rcu should be changed. But until then, I rather not add
> > another conditional to the core RCU code.
> 
> Also, call_rcu*() is called from several hot paths. This location is
> not a hot path, and actually, it is in fact rather slow. That's another
> reason not to add the logic into the RCU code if just adding it to
> tracepoints is sufficient.

Given that your reason for having this RCU-specific logic in tracepoint.c
rather than within call_rcu*() is not slowing down a fast-path, how about
creating a new call_rcu_early() and call_rcu_sched_early() which can be
called in normal operation and at early boot ?

This would allow us to keep the RCU logic within the RCU implementation
rather than strongly coupling it with the tracepoint code.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-14 16:41 [PATCH 0/3] tracing: Enable tracepoints early and allow printk to use them Steven Rostedt
2014-12-14 16:41 ` [PATCH 1/3] tracepoints: Do not use call_rcu_sched() before early_initcall() Steven Rostedt
2014-12-14 16:53   ` Steven Rostedt
2014-12-14 18:08     ` Paul E. McKenney
2014-12-14 18:15       ` Steven Rostedt
2014-12-14 18:18         ` Paul E. McKenney
2014-12-14 18:25           ` Steven Rostedt
2014-12-14 20:23             ` Paul E. McKenney
2014-12-14 17:05   ` Mathieu Desnoyers
2014-12-14 17:14     ` Steven Rostedt
2014-12-14 17:21       ` Steven Rostedt
2014-12-14 17:29         ` Mathieu Desnoyers [this message]
2014-12-14 17:44           ` Steven Rostedt
2014-12-14 18:13             ` Paul E. McKenney
2014-12-14 16:41 ` [PATCH 2/3] tracing: Move enabling tracepoints to just after mm_init() Steven Rostedt
2014-12-14 18:14   ` Paul E. McKenney
2014-12-14 18:20     ` Steven Rostedt
2014-12-14 20:26       ` Paul E. McKenney
2014-12-14 16:41 ` [PATCH 3/3] tracing: Add tp_printk cmdline to have tracepoints go to printk() Steven Rostedt
2014-12-14 17:07 ` [PATCH 0/3] tracing: Enable tracepoints early and allow printk to use them Steven Rostedt

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