Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751913AbdHaHeA (ORCPT ); Thu, 31 Aug 2017 03:34:00 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:58938 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751309AbdHaHbw (ORCPT ); Thu, 31 Aug 2017 03:31:52 -0400 Message-Id: <20170831073054.911861725@linutronix.de> User-Agent: quilt/0.63-1 Date: Thu, 31 Aug 2017 09:16:22 +0200 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Ingo Molnar , Andrew Morton , Borislav Petkov , Sebastian Siewior , Nicholas Piggin , Don Zickus , Chris Metcalf , Ulrich Obergfell Subject: [patch 24/29] lockup_detector/perf: Implement init time perf validation References: <20170831071558.995235362@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=lockup_detector-perf--Implement-init-time-perf-validation.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2876 Lines: 90 The watchdog tries to create perf events even after it figured out that perf is not functional or the requested event is not supported. That's braindead as this can be done once at init time and if not supported the NMI watchdog can be turned off unconditonally. Implement the perf hardlockup detector functionality for that. This creates a new event create function, which will replace the unholy mess of the existing one in later patches. Signed-off-by: Thomas Gleixner --- include/linux/nmi.h | 8 ++++++-- kernel/watchdog_hld.c | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+), 2 deletions(-) --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -93,14 +93,18 @@ extern void hardlockup_detector_perf_sto extern void hardlockup_detector_perf_restart(void); extern void hardlockup_detector_perf_disable(void); extern void hardlockup_detector_perf_cleanup(void); +extern int hardlockup_detector_perf_init(void); #else static inline void hardlockup_detector_perf_stop(void) { } static inline void hardlockup_detector_perf_restart(void) { } static inline void hardlockup_detector_perf_disable(void) { } static inline void hardlockup_detector_perf_cleanup(void) { } -#if !defined(CONFIG_HAVE_NMI_WATCHDOG) +# if !defined(CONFIG_HAVE_NMI_WATCHDOG) +static int hardlockup_detector_perf_init(void) { return -ENODEV; } static inline void arch_touch_nmi_watchdog(void) {} -#endif +# else +static int hardlockup_detector_perf_init(void) { return 0; } +# endif #endif void watchdog_nmi_reconfigure(bool run); --- a/kernel/watchdog_hld.c +++ b/kernel/watchdog_hld.c @@ -238,6 +238,27 @@ int watchdog_nmi_enable(unsigned int cpu return 0; } +static int hardlockup_detector_event_create(void) +{ + unsigned int cpu = smp_processor_id(); + struct perf_event_attr *wd_attr; + struct perf_event *evt; + + wd_attr = &wd_hw_attr; + wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); + + /* Try to register using hardware perf events */ + evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL, + watchdog_overflow_callback, NULL); + if (IS_ERR(evt)) { + pr_info("Perf event create on CPU %d failed with %ld\n", cpu, + PTR_ERR(evt)); + return PTR_ERR(evt); + } + this_cpu_write(watchdog_ev, evt); + return 0; +} + /** * hardlockup_detector_perf_disable - Disable the local event */ @@ -315,3 +336,19 @@ void __init hardlockup_detector_perf_res perf_event_enable(event); } } + +/** + * hardlockup_detector_perf_init - Probe whether NMI event is available at all + */ +int __init hardlockup_detector_perf_init(void) +{ + int ret = hardlockup_detector_event_create(); + + if (ret) { + pr_info("Perf NMI watchdog permanetely disabled\n"); + } else { + perf_event_release_kernel(this_cpu_read(watchdog_ev)); + this_cpu_write(watchdog_ev, NULL); + } + return ret; +}