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Date: Wed, 17 Dec 2008 12:50:10 -0500 From: Steven Rostedt <srostedt@...hat.com> To: dsaxena@...xity.net Cc: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org> Subject: Re: TSC not updating after resume: Bug or Feature? I added Peter Zijlstra too, since he works on the cpu clock as well. -- Steve On Wed, 2008-12-17 at 09:27 -0800, Deepak Saxena wrote: > Hi, > > I am using ftrace to get a detailed timing analysis of the resume process > on the OLPC XO laptop and am seeing that when we start running again, the > system timestamep is not being updated for several (hundreds of) thousands > of cycles (~2000 ftrace entries). From following the ftrace, what is > happening is that the clocksource is not updated until we run the cpu_idle() > thread due to an explicit scheduling operation in the resume path that occurs > via call to msleep from pci_set_power_state(). As I'm still fully groking the > timekeeping code, the question(s) I have is whether this is expected behaviour > and I should not assume valid timestamp data in the initial bits of the suspend path, > whether this is an OLPC-specific bug, or whether I've uncovered a generic bug in > the timekeeping implementation. This is on 2.6.27.7 as I've not gotten 28-rc > up and running on the XO but can move that up in priority if this behaviour > is different in newer kernels. > > Thanks, > ~Deepak > > # dsaxena: Return from firmware > do_suspend_trac-1267 [00] 154.925216: restore_processor_state <-ret_point > do_suspend_trac-1267 [00] 154.925216: enable_sep_cpu <-restore_processor_state > do_suspend_trac-1267 [00] 154.925216: olpc_fixup_wakeup <-olpc_pm_enter > do_suspend_trac-1267 [00] 154.925216: geode_get_dev_base <-olpc_fixup_wakeup > do_suspend_trac-1267 [00] 154.925216: olpc_ec_cmd <-olpc_fixup_wakeup > do_suspend_trac-1267 [00] 154.925216: _spin_lock_irqsave <-olpc_ec_cmd > do_suspend_trac-1267 [00] 154.925216: __wait_on_ibf <-olpc_ec_cmd > do_suspend_trac-1267 [00] 154.925216: printk <-olpc_ec_cmd > do_suspend_trac-1267 [00] 154.925216: vprintk <-printk > do_suspend_trac-1267 [00] 154.925216: _spin_lock <-vprintk > do_suspend_trac-1267 [00] 154.925216: emit_log_char <-vprintk > do_suspend_trac-1267 [00] 154.925216: emit_log_char <-vprintk > .... > # pci_set_power_state() calls msleep(10) as per PCI spec > do_suspend_trac-1267 [00] 154.925216: msleep <-pci_set_power_state > do_suspend_trac-1267 [00] 154.925216: msecs_to_jiffies <-msleep > do_suspend_trac-1267 [00] 154.925216: schedule_timeout_uninterruptible <-msleep > do_suspend_trac-1267 [00] 154.925216: schedule_timeout <-schedule_timeout_uninterruptible > do_suspend_trac-1267 [00] 154.925216: init_timer_on_stack <-schedule_timeout > do_suspend_trac-1267 [00] 154.925216: __init_timer <-init_timer_on_stack > do_suspend_trac-1267 [00] 154.925216: __mod_timer <-schedule_timeout > do_suspend_trac-1267 [00] 154.925216: __timer_stats_timer_set_start_info <-__mod_timer > do_suspend_trac-1267 [00] 154.925216: lock_timer_base <-__mod_timer > do_suspend_trac-1267 [00] 154.925216: _spin_lock_irqsave <-lock_timer_base > do_suspend_trac-1267 [00] 154.925216: internal_add_timer <-__mod_timer > do_suspend_trac-1267 [00] 154.925216: _spin_unlock_irqrestore <-__mod_timer > do_suspend_trac-1267 [00] 154.925216: _spin_lock <-schedule > do_suspend_trac-1267 [00] 154.925216: marker_probe_cb <-schedule > do_suspend_trac-1267 [00] 154.925216: _spin_unlock <-tracing_record_cmdline > do_suspend_trac-1267 [00] 154.925216: __switch_to <-schedule > <idle>-0 [00] 154.925216: _spin_unlock_irq <-finish_task_switch > <idle>-0 [00] 154.925216: tick_nohz_stop_sched_tick <-cpu_idle > <idle>-0 [00] 154.925216: ktime_get <-tick_nohz_stop_sched_tick > <idle>-0 [00] 154.925216: ktime_get_ts <-ktime_get > <idle>-0 [00] 154.925216: getnstimeofday <-ktime_get_ts > <idle>-0 [00] 154.925216: set_normalized_timespec <-ktime_get_ts > <idle>-0 [00] 154.925216: get_next_timer_interrupt <-tick_nohz_stop_sched_tick > <idle>-0 [00] 154.925216: _spin_lock <-get_next_timer_interrupt > <idle>-0 [00] 154.925216: _spin_unlock <-get_next_timer_interrupt > <idle>-0 [00] 154.925216: hrtimer_get_next_event <-get_next_timer_interrupt > <idle>-0 [00] 154.925216: _spin_lock_irqsave <-hrtimer_get_next_event > <idle>-0 [00] 154.925216: _spin_unlock_irqrestore <-hrtimer_get_next_event > <idle>-0 [00] 154.925216: rcu_needs_cpu <-tick_nohz_stop_sched_tick > <idle>-0 [00] 154.925216: rcu_pending <-rcu_needs_cpu > <idle>-0 [00] 154.925216: __rcu_pending <-rcu_pending > <idle>-0 [00] 154.925216: __rcu_pending <-rcu_pending > <idle>-0 [00] 154.925216: rcu_pending <-cpu_idle > <idle>-0 [00] 154.925216: __rcu_pending <-rcu_pending > <idle>-0 [00] 154.925216: __rcu_pending <-rcu_pending > <idle>-0 [00] 154.925216: default_idle <-cpu_idle > <idle>-0 [00] 154.925216: do_IRQ <-common_interrupt > <idle>-0 [00] 154.925216: irq_enter <-do_IRQ > <idle>-0 [00] 154.925216: tick_nohz_stop_idle <-irq_enter > <idle>-0 [00] 154.925216: ktime_get <-tick_nohz_stop_idle > <idle>-0 [00] 154.925216: ktime_get_ts <-ktime_get > <idle>-0 [00] 154.925216: getnstimeofday <-ktime_get_ts > <idle>-0 [00] 154.925216: set_normalized_timespec <-ktime_get_ts > <idle>-0 [00] 154.925216: ktime_get <-sched_clock_tick > <idle>-0 [00] 154.925216: ktime_get_ts <-ktime_get > <idle>-0 [00] 154.925216: getnstimeofday <-ktime_get_ts > <idle>-0 [00] 154.925216: set_normalized_timespec <-ktime_get_ts > # ktime_get_ts() calls getnstimeofday() which ends up calling clocksource_read() > # thus updating the kernel timestamp. note that we call getnstimeofday() > # twice above but for some reason they do not impact the time stamp... > # There is an IRQ in here, possibly an HRT-driven IRQ and I'm wondering > # if that is kicking the TSC into ticking? > <idle>-0 [00] 154.929837: touch_softlockup_watchdog <-sched_clock_idle_wakeup_event > <idle>-0 [00] 154.929839: tick_nohz_update_jiffies <-irq_enter > > > ~Deepak > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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