Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755986AbYJAJDy (ORCPT ); Wed, 1 Oct 2008 05:03:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754703AbYJAI56 (ORCPT ); Wed, 1 Oct 2008 04:57:58 -0400 Received: from mtagate5.de.ibm.com ([195.212.29.154]:33580 "EHLO mtagate5.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754674AbYJAI5x (ORCPT ); Wed, 1 Oct 2008 04:57:53 -0400 Message-Id: <20081001084129.581466549@de.ibm.com> References: <20081001083317.782967473@de.ibm.com> User-Agent: quilt/0.46-1 Date: Wed, 01 Oct 2008 10:33:34 +0200 From: Martin Schwidefsky To: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Cc: Heiko Carstens , Martin Schwidefsky Subject: [patch 17/21] nohz: Fix __udelay. Content-Disposition: inline; filename=116-udelay-torture.diff Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4909 Lines: 165 From: Heiko Carstens rcutorture reveals that our __udelay implementation is still buggy, since it might schedule tasklets, but prevents their execution: NOHZ: local_softirq_pending 42 NOHZ: local_softirq_pending 02 NOHZ: local_softirq_pending 142 NOHZ: local_softirq_pending 02 To fix this we make sure that only the clock comparator interrupt is enabled when the enabled wait psw is loaded. Also no code gets called anymore which might schedule tasklets. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/time.c | 2 + arch/s390/lib/delay.c | 88 +++++++++++++++++++++++++++++------------------- 2 files changed, 56 insertions(+), 34 deletions(-) Index: quilt-2.6/arch/s390/kernel/time.c =================================================================== --- quilt-2.6.orig/arch/s390/kernel/time.c +++ quilt-2.6/arch/s390/kernel/time.c @@ -169,6 +169,8 @@ void init_cpu_timer(void) static void clock_comparator_interrupt(__u16 code) { + if (S390_lowcore.clock_comparator == -1ULL) + set_clock_comparator(S390_lowcore.clock_comparator); } static void etr_timing_alert(struct etr_irq_parm *); Index: quilt-2.6/arch/s390/lib/delay.c =================================================================== --- quilt-2.6.orig/arch/s390/lib/delay.c +++ quilt-2.6/arch/s390/lib/delay.c @@ -1,14 +1,9 @@ /* - * arch/s390/lib/delay.c * Precise Delay Loops for S390 * - * S390 version - * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation - * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com), - * - * Derived from "arch/i386/lib/delay.c" - * Copyright (C) 1993 Linus Torvalds - * Copyright (C) 1997 Martin Mares + * Copyright IBM Corp. 1999,2008 + * Author(s): Martin Schwidefsky , + * Heiko Carstens , */ #include @@ -29,30 +24,31 @@ void __delay(unsigned long loops) asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1)); } -/* - * Waits for 'usecs' microseconds using the TOD clock comparator. - */ -void __udelay(unsigned long usecs) +static void __udelay_disabled(unsigned long usecs) { - u64 end, time, old_cc = 0; - unsigned long flags, cr0, mask, dummy; - int irq_context; + unsigned long mask, cr0, cr0_saved; + u64 clock_saved; - irq_context = in_interrupt(); - if (!irq_context) - local_bh_disable(); - local_irq_save(flags); - if (raw_irqs_disabled_flags(flags)) { - old_cc = local_tick_disable(); - S390_lowcore.clock_comparator = -1ULL; - __ctl_store(cr0, 0, 0); - dummy = (cr0 & 0xffff00e0) | 0x00000800; - __ctl_load(dummy , 0, 0); - mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT; - } else - mask = psw_kernel_bits | PSW_MASK_WAIT | - PSW_MASK_EXT | PSW_MASK_IO; + clock_saved = local_tick_disable(); + set_clock_comparator(get_clock() + ((u64) usecs << 12)); + __ctl_store(cr0_saved, 0, 0); + cr0 = (cr0_saved & 0xffff00e0) | 0x00000800; + __ctl_load(cr0 , 0, 0); + mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT; + trace_hardirqs_on(); + __load_psw_mask(mask); + local_irq_disable(); + __ctl_load(cr0_saved, 0, 0); + local_tick_enable(clock_saved); + set_clock_comparator(S390_lowcore.clock_comparator); +} +static void __udelay_enabled(unsigned long usecs) +{ + unsigned long mask; + u64 end, time; + + mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO; end = get_clock() + ((u64) usecs << 12); do { time = end < S390_lowcore.clock_comparator ? @@ -62,13 +58,37 @@ void __udelay(unsigned long usecs) __load_psw_mask(mask); local_irq_disable(); } while (get_clock() < end); + set_clock_comparator(S390_lowcore.clock_comparator); +} - if (raw_irqs_disabled_flags(flags)) { - __ctl_load(cr0, 0, 0); - local_tick_enable(old_cc); +/* + * Waits for 'usecs' microseconds using the TOD clock comparator. + */ +void __udelay(unsigned long usecs) +{ + unsigned long flags; + + preempt_disable(); + local_irq_save(flags); + if (in_irq()) { + __udelay_disabled(usecs); + goto out; + } + if (in_softirq()) { + if (raw_irqs_disabled_flags(flags)) + __udelay_disabled(usecs); + else + __udelay_enabled(usecs); + goto out; } - if (!irq_context) + if (raw_irqs_disabled_flags(flags)) { + local_bh_disable(); + __udelay_disabled(usecs); _local_bh_enable(); - set_clock_comparator(S390_lowcore.clock_comparator); + goto out; + } + __udelay_enabled(usecs); +out: local_irq_restore(flags); + preempt_enable(); } -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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/