| Message ID | 1426695946-21705-1-git-send-email-geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
On Wednesday, March 18, 2015 05:25:46 PM Geert Uytterhoeven wrote: > The PM Domain code uses ktime_get() to perform various latency > measurements. However, if ktime_get() is called while timekeeping is > suspended, the following warning is printed: > > WARNING: CPU: 0 PID: 1340 at kernel/time/timekeeping.c:576 ktime_get+0x30/0xf4() > > This happens when resuming the PM Domain that contains the clock events > source. Chain of operations is: > > timekeeping_resume() > { > clockevents_resume() > sh_cmt_clock_event_resume() > pm_genpd_syscore_poweron() > pm_genpd_sync_poweron() > genpd_power_on() > ktime_get(), but timekeeping_suspended == 1 > ... > timekeeping_suspended = 0; > } > > Skip all latency measurements if timekeeping is suspended to fix this. I don't think that this is where we should fix it. At least using timekeeping_suspended outside of the timekeeping core would not be welcome by its maintainers. > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > I'm not sure if this is needed for all latency measurements. > So far I only encountered it while powering-on a clock domain during > resume from s2ram. The problem seems to be that the clock domain is powered on in a syscore resume routine which happens to be called before timekeeping_resume(). It looks like we either need to force the right ordering somehow or have a special variant of GENPD_DEV_TIMED_CALLBACK() for syscore suspend/resume that won't do the latency measurement at all (which doesn't make much sense at this point, because time is effectively "frozen" then). Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Rafael, On Wed, Mar 18, 2015 at 11:30 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > On Wednesday, March 18, 2015 05:25:46 PM Geert Uytterhoeven wrote: >> The PM Domain code uses ktime_get() to perform various latency >> measurements. However, if ktime_get() is called while timekeeping is >> suspended, the following warning is printed: >> >> WARNING: CPU: 0 PID: 1340 at kernel/time/timekeeping.c:576 ktime_get+0x30/0xf4() >> >> This happens when resuming the PM Domain that contains the clock events >> source. Chain of operations is: >> >> timekeeping_resume() >> { >> clockevents_resume() >> sh_cmt_clock_event_resume() >> pm_genpd_syscore_poweron() >> pm_genpd_sync_poweron() >> genpd_power_on() >> ktime_get(), but timekeeping_suspended == 1 >> ... >> timekeeping_suspended = 0; >> } >> >> Skip all latency measurements if timekeeping is suspended to fix this. > > I don't think that this is where we should fix it. At least using > timekeeping_suspended outside of the timekeeping core would not be > welcome by its maintainers. It's a public symbol, declared in a header file ;-) >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> >> --- >> I'm not sure if this is needed for all latency measurements. >> So far I only encountered it while powering-on a clock domain during >> resume from s2ram. > > The problem seems to be that the clock domain is powered on in a > syscore resume routine which happens to be called before timekeeping_resume(). The clock domain is powered on from _within_ timekeeping_resume(). > It looks like we either need to force the right ordering somehow or have a > special variant of GENPD_DEV_TIMED_CALLBACK() for syscore suspend/resume that > won't do the latency measurement at all (which doesn't make much sense at > this point, because time is effectively "frozen" then). That's an option. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index 45937f88e77c8889..ab2398cfcebb7732 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c @@ -18,6 +18,7 @@ #include <linux/sched.h> #include <linux/suspend.h> #include <linux/export.h> +#include <linux/timekeeping.h> #define GENPD_DEV_CALLBACK(genpd, type, callback, dev) \ ({ \ @@ -33,16 +34,24 @@ #define GENPD_DEV_TIMED_CALLBACK(genpd, type, callback, dev, field, name) \ ({ \ - ktime_t __start = ktime_get(); \ - type __retval = GENPD_DEV_CALLBACK(genpd, type, callback, dev); \ - s64 __elapsed = ktime_to_ns(ktime_sub(ktime_get(), __start)); \ - struct gpd_timing_data *__td = &dev_gpd_data(dev)->td; \ - if (!__retval && __elapsed > __td->field) { \ - __td->field = __elapsed; \ - dev_dbg(dev, name " latency exceeded, new value %lld ns\n", \ - __elapsed); \ - genpd->max_off_time_changed = true; \ - __td->constraint_changed = true; \ + type __retval; \ + if (unlikely(timekeeping_suspended)) { \ + dev_dbg(dev, "Skipping %s timings\n", #callback); \ + __retval = GENPD_DEV_CALLBACK(genpd, type, callback, dev); \ + } else { \ + ktime_t __start = ktime_get(); \ + type __ret = GENPD_DEV_CALLBACK(genpd, type, callback, dev); \ + s64 __elapsed = ktime_to_ns(ktime_sub(ktime_get(), __start)); \ + struct gpd_timing_data *__td = &dev_gpd_data(dev)->td; \ + if (!__ret && __elapsed > __td->field) { \ + __td->field = __elapsed; \ + dev_dbg(dev, \ + name " latency exceeded, new value %lld ns\n", \ + __elapsed); \ + genpd->max_off_time_changed = true; \ + __td->constraint_changed = true; \ + } \ + __retval = __ret; \ } \ __retval; \ }) @@ -161,6 +170,11 @@ static int genpd_power_on(struct generic_pm_domain *genpd) if (!genpd->power_on) return 0; + if (unlikely(timekeeping_suspended)) { + pr_debug("%s: Skipping %s timings\n", genpd->name, "power_on"); + return genpd->power_on(genpd); + } + time_start = ktime_get(); ret = genpd->power_on(genpd); if (ret) @@ -188,6 +202,11 @@ static int genpd_power_off(struct generic_pm_domain *genpd) if (!genpd->power_off) return 0; + if (unlikely(timekeeping_suspended)) { + pr_debug("%s: Skipping %s timings\n", genpd->name, "power_off"); + return genpd->power_off(genpd); + } + time_start = ktime_get(); ret = genpd->power_off(genpd); if (ret == -EBUSY)
The PM Domain code uses ktime_get() to perform various latency measurements. However, if ktime_get() is called while timekeeping is suspended, the following warning is printed: WARNING: CPU: 0 PID: 1340 at kernel/time/timekeeping.c:576 ktime_get+0x30/0xf4() This happens when resuming the PM Domain that contains the clock events source. Chain of operations is: timekeeping_resume() { clockevents_resume() sh_cmt_clock_event_resume() pm_genpd_syscore_poweron() pm_genpd_sync_poweron() genpd_power_on() ktime_get(), but timekeeping_suspended == 1 ... timekeeping_suspended = 0; } Skip all latency measurements if timekeeping is suspended to fix this. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- I'm not sure if this is needed for all latency measurements. So far I only encountered it while powering-on a clock domain during resume from s2ram. --- drivers/base/power/domain.c | 39 +++++++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 10 deletions(-)