From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 4/8] sched,rcu,tracing: Mark preempt_count_{add,sub}() notrace Date: Wed, 12 Feb 2020 16:02:11 +0100 Message-ID: <20200212150211.GS14897@hirez.programming.kicks-ass.net> References: <20200212093210.468391728@infradead.org> <20200212094107.838108888@infradead.org> <20200212092417.04c3da8c@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from bombadil.infradead.org ([198.137.202.133]:43304 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727231AbgBLPCh (ORCPT ); Wed, 12 Feb 2020 10:02:37 -0500 Content-Disposition: inline In-Reply-To: <20200212092417.04c3da8c@gandalf.local.home> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Steven Rostedt 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 On Wed, Feb 12, 2020 at 09:24:17AM -0500, Steven Rostedt wrote: > On Wed, 12 Feb 2020 10:32:14 +0100 > Peter Zijlstra 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. > 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.