From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:50934 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328AbdADOBT (ORCPT ); Wed, 4 Jan 2017 09:01:19 -0500 Subject: Patch "kernel/debug/debug_core.c: more properly delay for secondary CPUs" has been added to the 4.9-stable tree To: dianders@chromium.org, akpm@linux-foundation.org, briannorris@chromium.org, daniel.thompson@linaro.org, gregkh@linuxfoundation.org, jason.wessel@windriver.com, torvalds@linux-foundation.org Cc: , From: Date: Wed, 04 Jan 2017 15:00:24 +0100 Message-ID: <1483538424226228@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled kernel/debug/debug_core.c: more properly delay for secondary CPUs to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kernel-debug-debug_core.c-more-properly-delay-for-secondary-cpus.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 2d13bb6494c807bcf3f78af0e96c0b8615a94385 Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Wed, 14 Dec 2016 15:05:49 -0800 Subject: kernel/debug/debug_core.c: more properly delay for secondary CPUs From: Douglas Anderson commit 2d13bb6494c807bcf3f78af0e96c0b8615a94385 upstream. We've got a delay loop waiting for secondary CPUs. That loop uses loops_per_jiffy. However, loops_per_jiffy doesn't actually mean how many tight loops make up a jiffy on all architectures. It is quite common to see things like this in the boot log: Calibrating delay loop (skipped), value calculated using timer frequency.. 48.00 BogoMIPS (lpj=24000) In my case I was seeing lots of cases where other CPUs timed out entering the debugger only to print their stack crawls shortly after the kdb> prompt was written. Elsewhere in kgdb we already use udelay(), so that should be safe enough to use to implement our timeout. We'll delay 1 ms for 1000 times, which should give us a full second of delay (just like the old code wanted) but allow us to notice that we're done every 1 ms. [akpm@linux-foundation.org: simplifications, per Daniel] Link: http://lkml.kernel.org/r/1477091361-2039-1-git-send-email-dianders@chromium.org Signed-off-by: Douglas Anderson Reviewed-by: Daniel Thompson Cc: Jason Wessel Cc: Brian Norris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/debug/debug_core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -598,11 +598,11 @@ return_normal: /* * Wait for the other CPUs to be notified and be waiting for us: */ - time_left = loops_per_jiffy * HZ; + time_left = MSEC_PER_SEC; while (kgdb_do_roundup && --time_left && (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != online_cpus) - cpu_relax(); + udelay(1000); if (!time_left) pr_crit("Timed out waiting for secondary CPUs.\n"); Patches currently in stable-queue which might be from dianders@chromium.org are queue-4.9/kernel-debug-debug_core.c-more-properly-delay-for-secondary-cpus.patch