Re: [PATCH v12 3/3] tracing: Centralize preemptirq tracepoints and unify their usage

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Joel Fernandes <joelaf@google.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Cc: Android Kernel" <kernel-team@android.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Byungchul Park <byungchul.park@lge.com>,
	Ingo Molnar <mingo@redhat.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Glexiner <tglx@linutronix.de>,
	Tom Zanussi <tom.zanussi@linux.intel.com>,
	will.deacon@arm.com
Subject: Re: [PATCH v12 3/3] tracing: Centralize preemptirq tracepoints and unify their usage
Date: Wed, 8 Aug 2018 10:21:00 -0700	[thread overview]
Message-ID: <20180808172100.GW24813@linux.vnet.ibm.com> (raw)
In-Reply-To: <20180808122404.67bdb77b@gandalf.local.home>

On Wed, Aug 08, 2018 at 12:24:04PM -0400, Steven Rostedt wrote:
> On Wed, 8 Aug 2018 09:02:43 -0700
> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> 
> > > Which leaves us with sparc, arm, mips, sh and powerpc.
> > > 
> > > sh is almost dead, and powerpc can be fixed, which I guess leaves us
> > > with sparc, arm and mips.  
> > 
> > If we want to stick with the current srcu_read_lock() and srcu_read_unlock(),
> > you mean?  I would like that sort of outcome, at least assuming we are not
> > hammering any of the architectures.
> 
> I would go with the local_inc approach, and even add a
> srcu_read_un/lock_nmi() that does that if you want. Probably should add
> lockdep to detect if the _nmi calls is ever used along with non _nmi
> calls and complain about that.

Would it be reasonable to also add a check for non-_nmi calls being
used in both NMI and non-NMI contexts?

> But this will be something for the next merge window, not the one
> coming up.

Completely agreed!

							Thanx, Paul