Messages in this thread Patch in this message | | | Date | Fri, 9 Sep 2016 16:33:59 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH][RFC v5] timekeeping: Ignore the bogus sleep time if pm_trace is enabled |
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On Fri, 9 Sep 2016, Chen Yu wrote: > > I really have no idea why this is burried in x86 land. The pm_trace hackery > > issues mc146818_set_time() to fiddle with the RTC. So any implementation of > > this is affected. > OK, I've changed this patch according to this suggestion.
No you did not! You still have that silly x86 hackery in place.
> OK. I've moved most of the logic into the pm_trace component, > Once the mc146818_set_time has modified the RTC by pm_trace, > related flags will be set which indicates the unusable of RTC. > And timekeeping system is able to query these flags to decide whether > it should inject the sleep time. (We tried to make this patch as > simple as possible, but it looks like we have to deal with persistent > clock for x86, which makes this patch a little more complicated). > Here's the trial version of it, any suggestion would be appreciated:
It's overengineered and horrible.
> +unsigned int timekeeping_tainted;
It does not taint timekeeping. It just wreckages the RTC.
> +void pm_trace_taint_timekeeping(void) > +{ > + if (pm_trace_is_enabled()) { > + timekeeping_tainted |= TIMEKEEPING_RTC_TAINTED; > + if (arch_pm_trace_taint_pclock()) > + timekeeping_tainted |= TIMEKEEPING_PERSISTENT_CLOCK_TAINTED; > + }
Why would you need all these flags?
> +static inline int pm_trace_rtc_is_tainted(void) > +{ > + return (timekeeping_tainted & TIMEKEEPING_RTC_TAINTED) ? > + 1 : 0;
ever heard about bool?
> +} > +
> +extern void pm_trace_untaint_timekeeping(void);
And how exactly do you untaint it? Just by clearing the flags. That makes the RTC time magically correct again?
> +int arch_pm_trace_taint_pclock(void) > +{ > + return (x86_platform.get_wallclock == mach_get_cmos_time); > +}
Groan. I told you to do it in the mc14xxx related places. There are not that many in the kernel
Here is a completely uncompiled/untested patch which should address the issue in a halfways clean way.
Thanks,
tglx
--- a/arch/x86/kernel/rtc.c +++ b/arch/x86/kernel/rtc.c @@ -64,6 +64,15 @@ void mach_get_cmos_time(struct timespec unsigned int status, year, mon, day, hour, min, sec, century = 0; unsigned long flags; + /* + * If pm trace abused the RTC as storage set the timespec to 0 + * which tells the caller that this RTC value is bogus. + */ + if (!pm_trace_rtc_valid()) { + now->tv_sec = now->tv_nsec = 0; + return; + } + spin_lock_irqsave(&rtc_lock, flags); /* --- a/drivers/base/power/trace.c +++ b/drivers/base/power/trace.c @@ -74,6 +74,7 @@ #define DEVSEED (7919) +bool pm_trace_rtc_abused __read_mostly; static unsigned int dev_hash_value; static int set_magic_time(unsigned int user, unsigned int file, unsigned int device) @@ -104,6 +105,7 @@ static int set_magic_time(unsigned int u time.tm_min = (n % 20) * 3; n /= 20; mc146818_set_time(&time); + pm_trace_rtc_abused = true; return n ? -1 : 0; } --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -189,6 +189,13 @@ static inline void cmos_write_bank2(unsi static int cmos_read_time(struct device *dev, struct rtc_time *t) { + /* + * If pmtrace abused the RTC for storage tell the caller that it is + * unusable. + */ + if (!pm_trace_rtc_valid()) + return -EIO; + /* REVISIT: if the clock has a "century" register, use * that instead of the heuristic in mc146818_get_time(). * That'll make Y3K compatility (year > 2070) easy! --- a/include/linux/mc146818rtc.h +++ b/include/linux/mc146818rtc.h @@ -16,6 +16,7 @@ #include <asm/mc146818rtc.h> /* register access macros */ #include <linux/bcd.h> #include <linux/delay.h> +#include <linux/pm-trace.h> #ifdef __KERNEL__ #include <linux/spinlock.h> /* spinlock_t */ --- a/include/linux/pm-trace.h +++ b/include/linux/pm-trace.h @@ -6,6 +6,12 @@ #include <linux/types.h> extern int pm_trace_enabled; +extern bool pm_trace_rtc_abused; + +static inline bool pm_trace_rtc_valid(void) +{ + return !pm_trace_rtc_abused; +} static inline int pm_trace_is_enabled(void) { @@ -24,6 +30,7 @@ extern int show_trace_dev_match(char *bu #else +static inline bool pm_trace_rtc_valid(void) { return true; } static inline int pm_trace_is_enabled(void) { return 0; } #define TRACE_DEVICE(dev) do { } while (0)
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