[2/3] watchdog: control hard lockup detection default

Message ID	1406196811-5384-3-git-send-email-drjones@redhat.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <kvm-owner@kernel.org> From: Andrew Jones <drjones@redhat.com> To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: uobergfe@redhat.com, dzickus@redhat.com, pbonzini@redhat.com, akpm@linux-foundation.org, mingo@redhat.com Subject: [PATCH 2/3] watchdog: control hard lockup detection default Date: Thu, 24 Jul 2014 12:13:30 +0200 Message-Id: <1406196811-5384-3-git-send-email-drjones@redhat.com> In-Reply-To: <1406196811-5384-1-git-send-email-drjones@redhat.com> References: <1406196811-5384-1-git-send-email-drjones@redhat.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk

diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 447775ee2c4b0..72aacf4e3d539 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -17,11 +17,20 @@ #if defined(CONFIG_HAVE_NMI_WATCHDOG) || defined(CONFIG_HARDLOCKUP_DETECTOR) #include <asm/nmi.h> extern void touch_nmi_watchdog(void); +extern void watchdog_enable_hardlockup_detector(bool val); +extern bool watchdog_hardlockup_detector_is_enabled(void); #else static inline void touch_nmi_watchdog(void) { touch_softlockup_watchdog(); } +static inline void watchdog_enable_hardlockup_detector(bool) +{ +} +static inline bool watchdog_hardlockup_detector_is_enabled(void) +{ + return true; +} #endif /* diff --git a/kernel/watchdog.c b/kernel/watchdog.c index c985a21926545..34eca29e28a4c 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -63,6 +63,25 @@ static unsigned long soft_lockup_nmi_warn; static int hardlockup_panic = CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE; +static bool hardlockup_detector_enabled = true; +/* + * We may not want to enable hard lockup detection by default in all cases, + * for example when running the kernel as a guest on a hypervisor. In these + * cases this function can be called to disable hard lockup detection. This + * function should only be executed once by the boot processor before the + * kernel command line parameters are parsed, because otherwise it is not + * possible to override this in hardlockup_panic_setup(). + */ +void watchdog_enable_hardlockup_detector(bool val) +{ + hardlockup_detector_enabled = val; +} + +bool watchdog_hardlockup_detector_is_enabled(void) +{ + return hardlockup_detector_enabled; +} + static int __init hardlockup_panic_setup(char *str) { if (!strncmp(str, "panic", 5)) @@ -71,6 +90,14 @@ static int __init hardlockup_panic_setup(char *str) hardlockup_panic = 0; else if (!strncmp(str, "0", 1)) watchdog_user_enabled = 0; + else if (!strncmp(str, "1", 1) || !strncmp(str, "2", 1)) { + /* + * Setting 'nmi_watchdog=1' or 'nmi_watchdog=2' (legacy option) + * has the same effect. + */ + watchdog_user_enabled = 1; + watchdog_enable_hardlockup_detector(true); + } return 1; } __setup("nmi_watchdog=", hardlockup_panic_setup); @@ -451,6 +478,15 @@ static int watchdog_nmi_enable(unsigned int cpu) struct perf_event_attr *wd_attr; struct perf_event *event = per_cpu(watchdog_ev, cpu); + /* + * Some kernels need to default hard lockup detection to + * 'disabled', for example a guest on a hypervisor. + */ + if (!watchdog_hardlockup_detector_is_enabled()) { + event = ERR_PTR(-ENOENT); + goto handle_err; + } + /* is it already setup and enabled? */ if (event && event->state > PERF_EVENT_STATE_OFF) goto out; @@ -465,6 +501,7 @@ static int watchdog_nmi_enable(unsigned int cpu) /* Try to register using hardware perf events */ event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); +handle_err: /* save cpu0 error for future comparision */ if (cpu == 0 && IS_ERR(event)) cpu0_err = PTR_ERR(event); @@ -610,11 +647,13 @@ int proc_dowatchdog(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int err, old_thresh, old_enabled; + bool old_hardlockup; static DEFINE_MUTEX(watchdog_proc_mutex); mutex_lock(&watchdog_proc_mutex); old_thresh = ACCESS_ONCE(watchdog_thresh); old_enabled = ACCESS_ONCE(watchdog_user_enabled); + old_hardlockup = watchdog_hardlockup_detector_is_enabled(); err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (err || !write) @@ -626,15 +665,17 @@ int proc_dowatchdog(struct ctl_table *table, int write, * disabled. The 'watchdog_running' variable check in * watchdog_*_all_cpus() function takes care of this. */ - if (watchdog_user_enabled && watchdog_thresh) + if (watchdog_user_enabled && watchdog_thresh) { + watchdog_enable_hardlockup_detector(true); err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh); - else + } else watchdog_disable_all_cpus(); /* Restore old values on failure */ if (err) { watchdog_thresh = old_thresh; watchdog_user_enabled = old_enabled; + watchdog_enable_hardlockup_detector(old_hardlockup); } out: mutex_unlock(&watchdog_proc_mutex);

[2/3] watchdog: control hard lockup detection default

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