Each CPU should be monitored for hardlockups every watchdog_thresh seconds. Since all the CPUs in the system are monitored by the same timer and the timer interrupt is rotated among the monitored CPUs, the timer must expire every watchdog_thresh/N seconds; where N is the number of monitored CPUs. Use the new member of struct hld_data, ticks_per_cpu, to store the aforementioned quantity.
The ticks-per-CPU quantity is updated every time the number of monitored CPUs changes: when the watchdog is enabled or disabled for a specific CPU. If the timer is used in periodic mode, it needs to be adjusted to reflect the new expected expiration. Cc: Ashok Raj <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Tony Luck <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Jacob Pan <[email protected]> Cc: "Rafael J. Wysocki" <[email protected]> Cc: Don Zickus <[email protected]> Cc: Nicholas Piggin <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Babu Moger <[email protected]> Cc: Mathieu Desnoyers <[email protected]> Cc: Masami Hiramatsu <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Philippe Ombredanne <[email protected]> Cc: Colin Ian King <[email protected]> Cc: Byungchul Park <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: "Luis R. Rodriguez" <[email protected]> Cc: Waiman Long <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Randy Dunlap <[email protected]> Cc: Davidlohr Bueso <[email protected]> Cc: Marc Zyngier <[email protected]> Cc: Kai-Heng Feng <[email protected]> Cc: Konrad Rzeszutek Wilk <[email protected]> Cc: David Rientjes <[email protected]> Cc: Stephane Eranian <[email protected]> Cc: Suravee Suthikulpanit <[email protected]> Cc: "Ravi V. Shankar" <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Ricardo Neri <[email protected]> --- arch/x86/include/asm/hpet.h | 1 + arch/x86/kernel/watchdog_hld_hpet.c | 46 +++++++++++++++++++++++++++-- 2 files changed, 44 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/hpet.h b/arch/x86/include/asm/hpet.h index 31fc27508cf3..64acacce095d 100644 --- a/arch/x86/include/asm/hpet.h +++ b/arch/x86/include/asm/hpet.h @@ -114,6 +114,7 @@ struct hpet_hld_data { bool has_periodic; u32 num; u64 ticks_per_second; + u64 ticks_per_cpu; u32 handling_cpu; u32 enabled_cpus; struct msi_msg msi_msg; diff --git a/arch/x86/kernel/watchdog_hld_hpet.c b/arch/x86/kernel/watchdog_hld_hpet.c index dff4dadabd4c..74aeb0535d08 100644 --- a/arch/x86/kernel/watchdog_hld_hpet.c +++ b/arch/x86/kernel/watchdog_hld_hpet.c @@ -45,6 +45,13 @@ static void kick_timer(struct hpet_hld_data *hdata, bool force) * are able to update the comparator before the counter reaches such new * value. * + * Each CPU must be monitored every watch_thresh seconds. Since the + * timer targets one CPU at a time, it must expire every + * + * ticks_per_cpu = watch_thresh * ticks_per_second /enabled_cpus + * + * as computed in update_ticks_per_cpu(). + * * Let it wrap around if needed. */ @@ -52,10 +59,10 @@ static void kick_timer(struct hpet_hld_data *hdata, bool force) return; if (hdata->has_periodic) - period = watchdog_thresh * hdata->ticks_per_second; + period = watchdog_thresh * hdata->ticks_per_cpu; count = hpet_readl(HPET_COUNTER); - new_compare = count + watchdog_thresh * hdata->ticks_per_second; + new_compare = count + watchdog_thresh * hdata->ticks_per_cpu; hpet_set_comparator(hdata->num, (u32)new_compare, (u32)period); } @@ -234,6 +241,27 @@ static int setup_hpet_irq(struct hpet_hld_data *hdata) return ret; } +/** + * update_ticks_per_cpu() - Update the number of HPET ticks per CPU + * @hdata: struct with the timer's the ticks-per-second and CPU mask + * + * From the overall ticks-per-second of the timer, compute the number of ticks + * after which the timer should expire to monitor each CPU every watch_thresh + * seconds. The ticks-per-cpu quantity is computed using the number of CPUs that + * the watchdog currently monitors. + */ +static void update_ticks_per_cpu(struct hpet_hld_data *hdata) +{ + u64 temp = hdata->ticks_per_second; + + /* Only update if there are monitored CPUs. */ + if (!hdata->enabled_cpus) + return; + + do_div(temp, hdata->enabled_cpus); + hdata->ticks_per_cpu = temp; +} + /** * hardlockup_detector_hpet_enable() - Enable the hardlockup detector * @cpu: CPU Index in which the watchdog will be enabled. @@ -246,13 +274,23 @@ void hardlockup_detector_hpet_enable(unsigned int cpu) { cpumask_set_cpu(cpu, to_cpumask(hld_data->cpu_monitored_mask)); - if (!hld_data->enabled_cpus++) { + hld_data->enabled_cpus++; + update_ticks_per_cpu(hld_data); + + if (hld_data->enabled_cpus == 1) { hld_data->handling_cpu = cpu; update_msi_destid(hld_data); /* Force timer kick when detector is just enabled */ kick_timer(hld_data, true); enable_timer(hld_data); } + + /* + * When in periodic mode, we only kick the timer here. Hence, + * as there are now more CPUs to monitor, we need to adjust the + * periodic expiration. + */ + kick_timer(hld_data, hld_data->has_periodic); } /** @@ -268,6 +306,8 @@ void hardlockup_detector_hpet_disable(unsigned int cpu) cpumask_clear_cpu(cpu, to_cpumask(hld_data->cpu_monitored_mask)); hld_data->enabled_cpus--; + update_ticks_per_cpu(hld_data); + if (hld_data->handling_cpu != cpu) return; -- 2.17.1
