Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753025Ab3JSPCg (ORCPT ); Sat, 19 Oct 2013 11:02:36 -0400 Received: from mail7.hitachi.co.jp ([133.145.228.42]:54563 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751315Ab3JSPCf (ORCPT ); Sat, 19 Oct 2013 11:02:35 -0400 Message-ID: <52629F08.2010609@hitachi.com> Date: Sun, 20 Oct 2013 00:02:32 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Petr Mladek Cc: Steven Rostedt , Frederic Weisbecker , Jiri Kosina , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH 2/6] x86: allow to call text_poke_bp during boot References: <1382106445-31468-3-git-send-email-pmladek@suse.cz> In-Reply-To: <1382106445-31468-3-git-send-email-pmladek@suse.cz> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2554 Lines: 85 (2013/10/18 23:27), Petr Mladek wrote: > We would like to use text_poke_bp in ftrace. It might be called also during > boot when the interupts are disabled. We need to enable them for syncing > the cores on each CPU. Otherwise, there might be a deadlock, see the > warning in "smp_call_function_many", kernel/smp.c:371. Steven, is this really needed? I think if this is the special use(e.g. boottime test), we'd better to run it after boot... Thank you, > > This change is taken from the current code in arch/x86/kernel/ftrace.c. > > Signed-off-by: Petr Mladek > --- > arch/x86/kernel/alternative.c | 20 +++++++++++++++++--- > 1 file changed, 17 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c > index f714316..13cae15 100644 > --- a/arch/x86/kernel/alternative.c > +++ b/arch/x86/kernel/alternative.c > @@ -629,6 +629,20 @@ static void do_sync_core(void *info) > sync_core(); > } > > +static void run_sync(void) > +{ > + int enable_irqs = irqs_disabled(); > + > + /* We may be called with interrupts disbled (on bootup). */ > + if (enable_irqs) > + local_irq_enable(); > + > + on_each_cpu(do_sync_core, NULL, 1); > + > + if (enable_irqs) > + local_irq_disable(); > +} > + > static bool bp_patching_in_progress; > static void *bp_int3_handler, *bp_int3_addr; > > @@ -688,7 +702,7 @@ void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler) > > text_poke_part(addr, &int3, sizeof(int3)); > > - on_each_cpu(do_sync_core, NULL, 1); > + run_sync(); > > if (len - sizeof(int3) > 0) { > /* patch all but the first byte */ > @@ -700,13 +714,13 @@ void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler) > * not necessary and we'd be safe even without it. But > * better safe than sorry (plus there's not only Intel). > */ > - on_each_cpu(do_sync_core, NULL, 1); > + run_sync(); > } > > /* patch the first byte */ > text_poke_part(addr, opcode, sizeof(int3)); > > - on_each_cpu(do_sync_core, NULL, 1); > + run_sync(); > > bp_patching_in_progress = false; > smp_wmb(); > -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/