From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v3 05/22] rcu: Make RCU IRQ enter/exit functions rely on in_nmi() Date: Wed, 19 Feb 2020 17:37:00 +0100 Message-ID: <20200219163700.GK18400@hirez.programming.kicks-ass.net> References: <20200219144724.800607165@infradead.org> <20200219150744.661923520@infradead.org> <20200219163156.GY2935@paulmck-ThinkPad-P72> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from merlin.infradead.org ([205.233.59.134]:33404 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726754AbgBSQh3 (ORCPT ); Wed, 19 Feb 2020 11:37:29 -0500 Content-Disposition: inline In-Reply-To: <20200219163156.GY2935@paulmck-ThinkPad-P72> Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org, mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, luto@kernel.org, tony.luck@intel.com, frederic@kernel.org, dan.carpenter@oracle.com, mhiramat@kernel.org On Wed, Feb 19, 2020 at 08:31:56AM -0800, Paul E. McKenney wrote: > On Wed, Feb 19, 2020 at 03:47:29PM +0100, Peter Zijlstra wrote: > > From: Paul E. McKenney > > > > The rcu_nmi_enter_common() and rcu_nmi_exit_common() functions take an > > "irq" parameter that indicates whether these functions are invoked from > > an irq handler (irq==true) or an NMI handler (irq==false). However, > > recent changes have applied notrace to a few critical functions such > > that rcu_nmi_enter_common() and rcu_nmi_exit_common() many now rely > > on in_nmi(). Note that in_nmi() works no differently than before, > > but rather that tracing is now prohibited in code regions where in_nmi() > > would incorrectly report NMI state. > > > > This commit therefore removes the "irq" parameter and inlines > > rcu_nmi_enter_common() and rcu_nmi_exit_common() into rcu_nmi_enter() > > and rcu_nmi_exit(), respectively. > > > > Signed-off-by: Paul E. McKenney > > Signed-off-by: Peter Zijlstra (Intel) > > Again, thank you. > > Would you like to also take the added comment for NOKPROBE_SYMBOL(), > or would you prefer that I carry that separately? (I dropped it for > now to avoid the conflict with the patch below.) > > Here is the latest version of that comment, posted by Steve Rostedt. > > Thanx, Paul > > /* > * All functions called in the breakpoint trap handler (e.g. do_int3() > * on x86), must not allow kprobes until the kprobe breakpoint handler > * is called, otherwise it can cause an infinite recursion. > * On some archs, rcu_nmi_enter() is called in the breakpoint handler > * before the kprobe breakpoint handler is called, thus it must be > * marked as NOKPROBE. > */ Oh right, let me stick that in a separate patch. Best we not loose that I suppose ;-)