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SubjectRe: [patch 24/29] lockup_detector/perf: Implement init time perf validation
On Thu, Aug 31, 2017 at 09:16:22AM +0200, Thomas Gleixner wrote:
> 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 <tglx@linutronix.de>
> ---
> 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; }

hardlockup_detector_perf_init needs to be 'inline' otherwise fails to
compile with CONFIG_HARDLOCKUP_DETECTOR_PERF turned off.


Cheers,
Don

> +# 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;
> +}
>
>

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