From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752517AbdASMD4 (ORCPT ); Thu, 19 Jan 2017 07:03:56 -0500 Received: from mx2.suse.de ([195.135.220.15]:52357 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752233AbdASMDy (ORCPT ); Thu, 19 Jan 2017 07:03:54 -0500 From: Jiri Slaby To: mingo@kernel.org Cc: linux-kernel@vger.kernel.org, Jiri Slaby , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org Subject: [PATCH] x86: make delay work in earlier stages Date: Thu, 19 Jan 2017 12:47:30 +0100 Message-Id: <20170119114730.2670-1-jslaby@suse.cz> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a panic happens during bootup, "Rebooting in X seconds.." is shown, but reboot happens immediatelly. It is because panic uses mdelay and mdelay calls internally __const_udelay which is broken while booting. The per_cpu cpu_info.loops_per_jiffy is not initialized yet, so __const_udelay actually multiplies the number of loops by zero. This results in __const_udelay to delay the execution only by a nanosecond or so. So check whether cpu_info.loops_per_jiffy is zero and use loops_per_jiffy in that case. mdelay will not be so precise, but it works relatively good. From the original (mdelay in rest_init): [ 0.170039] delaying 100ms [ 0.170828] done I get: [ 0.214042] delaying 100ms [ 0.313974] done I do not think the added check matters given we are about to spin the processor in the next few hundred cycles. Signed-off-by: Jiri Slaby Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: --- arch/x86/lib/delay.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c index 073d1f1a620b..aca0988f0e14 100644 --- a/arch/x86/lib/delay.c +++ b/arch/x86/lib/delay.c @@ -156,13 +156,14 @@ EXPORT_SYMBOL(__delay); inline void __const_udelay(unsigned long xloops) { + unsigned long lpf = this_cpu_read(cpu_info.loops_per_jiffy) ? : + loops_per_jiffy; int d0; xloops *= 4; asm("mull %%edx" :"=d" (xloops), "=&a" (d0) - :"1" (xloops), "0" - (this_cpu_read(cpu_info.loops_per_jiffy) * (HZ/4))); + :"1" (xloops), "0" (lpf * (HZ / 4))); __delay(++xloops); } -- 2.11.0