RE: [patch 012/100] acpi: fix of pmtimer overflow that make Cx states time incorrect

Shi, Alex
2009-04-23T09:25:27Z

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It was reported make some latop booting hang. and is not root caused now. :(
http://bugzilla.kernel.org/show_bug.cgi?id=13087

Alex
>-----Original Message-----
>From: Chris Wright [mailto:chrisw@sous-sol.org]
>Sent: 2009Äê4ÔÂ23ÈÕ 15:21
>To: linux-kernel@vger.kernel.org; stable@kernel.org
>Cc: Justin Forbes; Zwane Mwaikambo; Theodore Ts'o; Randy Dunlap; Dave Jones;
>Chuck Wolber; Chris Wedgwood; Michael Krufky; Chuck Ebbert; Domenico Andreoli;
>Willy Tarreau; Rodrigo Rubira Branco; Jake Edge; Eugene Teo;
>torvalds@linux-foundation.org; akpm@linux-foundation.org;
>alan@lxorguk.ukuu.org.uk; Len Brown; linux-acpi@vger.kernel.org; Shi, Alex;
>Pallipadi, Venkatesh; Zhao, Yakui; Brown, Len
>Subject: [patch 012/100] acpi: fix of pmtimer overflow that make Cx states time
>incorrect
>
>-stable review patch. If anyone has any objections, please let us know.
>---------------------
>
>From: alex.shi <alex.shi@intel.com>
>
>upstream commit: ff69f2bba67bd45514923aaedbf40fe351787c59
>
>We found Cx states time abnormal in our some of machines which have 16
>LCPUs, the C0 take too many time while system is really idle when kernel
>enabled tickless and highres. powertop output is below:
>
> PowerTOP version 1.9 (C) 2007 Intel Corporation
>
>Cn Avg residency P-states (frequencies)
>C0 (cpu running) (40.5%) 2.53 Ghz 0.0%
>C1 0.0ms ( 0.0%) 2.53 Ghz 0.0%
>C2 128.8ms (59.5%) 2.40 Ghz 0.0%
> 1.60 Ghz 100.0%
>
>Wakeups-from-idle per second : 4.7 interval: 20.0s
>no ACPI power usage estimate available
>
>Top causes for wakeups:
> 41.4% ( 24.9) <interrupt> : extra timer interrupt
> 20.2% ( 12.2) <kernel core> : usb_hcd_poll_rh_status
>(rh_timer_func)
>
>After tacking detailed for this issue, Yakui and I find it is due to 24
>bit PM timer overflows when some of cpu sleep more than 4 seconds. With
>tickless kernel, the CPU want to sleep as much as possible when system
>idle. But the Cx sleep time are recorded by pmtimer which length is
>determined by BIOS. The current Cx time was gotten in the following
>function from driver/acpi/processor_idle.c:
>
>static inline u32 ticks_elapsed(u32 t1, u32 t2)
>{
> if (t2 >= t1)
> return (t2 - t1);
> else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
> return (((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
> else
> return ((0xFFFFFFFF - t1) + t2);
>}
>
>If pmtimer is 24 bits and it take 5 seconds from t1 to t2, in above
>function, just about 1 seconds ticks was recorded. So the Cx time will be
>reduced about 4 seconds. and this is why we see above powertop output.
>
>To resolve this problem, Yakui and I use ktime_get() to record the Cx
>states time instead of PM timer as the following patch. the patch was
>tested with i386/x86_64 modes on several platforms.
>
>Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
>Tested-by: Alex Shi <alex.shi@intel.com>
>Signed-off-by: Alex Shi <alex.shi@intel.com>
>Signed-off-by: Yakui.zhao <yakui.zhao@intel.com>
>Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>Signed-off-by: Len Brown <len.brown@intel.com>
>Signed-off-by: Chris Wright <chrisw@sous-sol.org>
>---
> drivers/acpi/processor_idle.c | 63
>++++++++++++++++++------------------------
> 1 file changed, 27 insertions(+), 36 deletions(-)
>
>--- a/drivers/acpi/processor_idle.c
>+++ b/drivers/acpi/processor_idle.c
>@@ -64,7 +64,6 @@
> #define _COMPONENT ACPI_PROCESSOR_COMPONENT
> ACPI_MODULE_NAME("processor_idle");
> #define ACPI_PROCESSOR_FILE_POWER "power"
>-#define US_TO_PM_TIMER_TICKS(t) ((t * (PM_TIMER_FREQUENCY/1000)) /
>1000)
> #define PM_TIMER_TICK_NS (1000000000ULL/PM_TIMER_FREQUENCY)
> #define C2_OVERHEAD 1 /* 1us */
> #define C3_OVERHEAD 1 /* 1us */
>@@ -78,6 +77,10 @@ module_param(nocst, uint, 0000);
> static unsigned int latency_factor __read_mostly = 2;
> module_param(latency_factor, uint, 0644);
>
>+static s64 us_to_pm_timer_ticks(s64 t)
>+{
>+ return div64_u64(t * PM_TIMER_FREQUENCY, 1000000);
>+}
> /*
> * IBM ThinkPad R40e crashes mysteriously when going into C2 or C3.
> * For now disable this. Probably a bug somewhere else.
>@@ -159,25 +162,6 @@ static struct dmi_system_id __cpuinitdat
> {},
> };
>
>-static inline u32 ticks_elapsed(u32 t1, u32 t2)
>-{
>- if (t2 >= t1)
>- return (t2 - t1);
>- else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
>- return (((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
>- else
>- return ((0xFFFFFFFF - t1) + t2);
>-}
>-
>-static inline u32 ticks_elapsed_in_us(u32 t1, u32 t2)
>-{
>- if (t2 >= t1)
>- return PM_TIMER_TICKS_TO_US(t2 - t1);
>- else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
>- return PM_TIMER_TICKS_TO_US(((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
>- else
>- return PM_TIMER_TICKS_TO_US((0xFFFFFFFF - t1) + t2);
>-}
>
> /*
> * Callers should disable interrupts before the call and enable
>@@ -853,7 +837,8 @@ static inline void acpi_idle_do_entry(st
> static int acpi_idle_enter_c1(struct cpuidle_device *dev,
> struct cpuidle_state *state)
> {
>- u32 t1, t2;
>+ ktime_t kt1, kt2;
>+ s64 idle_time;
> struct acpi_processor *pr;
> struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
>
>@@ -871,14 +856,15 @@ static int acpi_idle_enter_c1(struct cpu
> return 0;
> }
>
>- t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
>+ kt1 = ktime_get_real();
> acpi_idle_do_entry(cx);
>- t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
>+ kt2 = ktime_get_real();
>+ idle_time = ktime_to_us(ktime_sub(kt2, kt1));
>
> local_irq_enable();
> cx->usage++;
>
>- return ticks_elapsed_in_us(t1, t2);
>+ return idle_time;
> }
>
> /**
>@@ -891,8 +877,9 @@ static int acpi_idle_enter_simple(struct
> {
> struct acpi_processor *pr;
> struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
>- u32 t1, t2;
>- int sleep_ticks = 0;
>+ ktime_t kt1, kt2;
>+ s64 idle_time;
>+ s64 sleep_ticks = 0;
>
> pr = __get_cpu_var(processors);
>
>@@ -925,18 +912,19 @@ static int acpi_idle_enter_simple(struct
> if (cx->type == ACPI_STATE_C3)
> ACPI_FLUSH_CPU_CACHE();
>
>- t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
>+ kt1 = ktime_get_real();
> /* Tell the scheduler that we are going deep-idle: */
> sched_clock_idle_sleep_event();
> acpi_idle_do_entry(cx);
>- t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
>+ kt2 = ktime_get_real();
>+ idle_time = ktime_to_us(ktime_sub(kt2, kt1));
>
> #if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
> /* TSC could halt in idle, so notify users */
> if (tsc_halts_in_c(cx->type))
> mark_tsc_unstable("TSC halts in idle");;
> #endif
>- sleep_ticks = ticks_elapsed(t1, t2);
>+ sleep_ticks = us_to_pm_timer_ticks(idle_time);
>
> /* Tell the scheduler how much we idled: */
> sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
>@@ -948,7 +936,7 @@ static int acpi_idle_enter_simple(struct
>
> acpi_state_timer_broadcast(pr, cx, 0);
> cx->time += sleep_ticks;
>- return ticks_elapsed_in_us(t1, t2);
>+ return idle_time;
> }
>
> static int c3_cpu_count;
>@@ -966,8 +954,10 @@ static int acpi_idle_enter_bm(struct cpu
> {
> struct acpi_processor *pr;
> struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
>- u32 t1, t2;
>- int sleep_ticks = 0;
>+ ktime_t kt1, kt2;
>+ s64 idle_time;
>+ s64 sleep_ticks = 0;
>+
>
> pr = __get_cpu_var(processors);
>
>@@ -1034,9 +1024,10 @@ static int acpi_idle_enter_bm(struct cpu
> ACPI_FLUSH_CPU_CACHE();
> }
>
>- t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
>+ kt1 = ktime_get_real();
> acpi_idle_do_entry(cx);
>- t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
>+ kt2 = ktime_get_real();
>+ idle_time = ktime_to_us(ktime_sub(kt2, kt1));
>
> /* Re-enable bus master arbitration */
> if (pr->flags.bm_check && pr->flags.bm_control) {
>@@ -1051,7 +1042,7 @@ static int acpi_idle_enter_bm(struct cpu
> if (tsc_halts_in_c(ACPI_STATE_C3))
> mark_tsc_unstable("TSC halts in idle");
> #endif
>- sleep_ticks = ticks_elapsed(t1, t2);
>+ sleep_ticks = us_to_pm_timer_ticks(idle_time);
> /* Tell the scheduler how much we idled: */
> sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
>
>@@ -1062,7 +1053,7 @@ static int acpi_idle_enter_bm(struct cpu
>
> acpi_state_timer_broadcast(pr, cx, 0);
> cx->time += sleep_ticks;
>- return ticks_elapsed_in_us(t1, t2);
>+ return idle_time;
> }
>
> struct cpuidle_driver acpi_idle_driver = {

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