schedule_work(&watchdog_work);
}
-static void clocksource_unstable(struct clocksource *cs, int64_t delta)
-{
- printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
- cs->name, delta);
- __clocksource_unstable(cs);
-}
-
/**
* clocksource_mark_unstable - mark clocksource unstable via watchdog
* @cs: clocksource to be marked unstable
static void clocksource_watchdog(unsigned long data)
{
struct clocksource *cs;
- cycle_t csnow, wdnow, delta;
+ cycle_t csnow, wdnow, cslast, wdlast, delta;
int64_t wd_nsec, cs_nsec;
int next_cpu, reset_pending;
delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
+ wdlast = cs->wd_last; /* save these in case we print them */
+ cslast = cs->cs_last;
cs->cs_last = csnow;
cs->wd_last = wdnow;
/* Check the deviation from the watchdog clocksource. */
if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) {
- clocksource_unstable(cs, cs_nsec - wd_nsec);
+ pr_warn("timekeeping watchdog: Marking clocksource '%s' as unstable, because the skew is too large:\n", cs->name);
+ pr_warn(" '%s' wd_now: %llx wd_last: %llx mask: %llx\n",
+ watchdog->name, wdnow, wdlast, watchdog->mask);
+ pr_warn(" '%s' cs_now: %llx cs_last: %llx mask: %llx\n",
+ cs->name, csnow, cslast, cs->mask);
+ __clocksource_unstable(cs);
continue;
}
* @shift: cycle to nanosecond divisor (power of two)
* @maxadj: maximum adjustment value to mult (~11%)
* @mask: bitmask for two's complement subtraction of non 64 bit counters
+ * @max_cyc: maximum cycle value before potential overflow (does not include
+ * any safety margin)
+ *
+ * NOTE: This function includes a safety margin of 50%, so that bad clock values
+ * can be detected.
*/
-u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask)
+u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc)
{
u64 max_nsecs, max_cycles;
/*
* Calculate the maximum number of cycles that we can pass to the
- * cyc2ns function without overflowing a 64-bit signed result. The
- * maximum number of cycles is equal to ULLONG_MAX/(mult+maxadj)
- * which is equivalent to the below.
- * max_cycles < (2^63)/(mult + maxadj)
- * max_cycles < 2^(log2((2^63)/(mult + maxadj)))
- * max_cycles < 2^(log2(2^63) - log2(mult + maxadj))
- * max_cycles < 2^(63 - log2(mult + maxadj))
- * max_cycles < 1 << (63 - log2(mult + maxadj))
- * Please note that we add 1 to the result of the log2 to account for
- * any rounding errors, ensure the above inequality is satisfied and
- * no overflow will occur.
+ * cyc2ns() function without overflowing a 64-bit result.
*/
- max_cycles = 1ULL << (63 - (ilog2(mult + maxadj) + 1));
+ max_cycles = ULLONG_MAX;
+ do_div(max_cycles, mult+maxadj);
/*
* The actual maximum number of cycles we can defer the clocksource is
max_cycles = min(max_cycles, mask);
max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
+ /* return the max_cycles value as well if requested */
+ if (max_cyc)
+ *max_cyc = max_cycles;
+
+ /* Return 50% of the actual maximum, so we can detect bad values */
+ max_nsecs >>= 1;
+
return max_nsecs;
}
/**
- * clocksource_max_deferment - Returns max time the clocksource can be deferred
- * @cs: Pointer to clocksource
+ * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles
+ * @cs: Pointer to clocksource to be updated
*
*/
-static u64 clocksource_max_deferment(struct clocksource *cs)
+static inline void clocksource_update_max_deferment(struct clocksource *cs)
{
- u64 max_nsecs;
-
- max_nsecs = clocks_calc_max_nsecs(cs->mult, cs->shift, cs->maxadj,
- cs->mask);
- /*
- * To ensure that the clocksource does not wrap whilst we are idle,
- * limit the time the clocksource can be deferred by 12.5%. Please
- * note a margin of 12.5% is used because this can be computed with
- * a shift, versus say 10% which would require division.
- */
- return max_nsecs - (max_nsecs >> 3);
+ cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
+ cs->maxadj, cs->mask,
+ &cs->max_cycles);
}
#ifndef CONFIG_ARCH_USES_GETTIMEOFFSET
void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
{
u64 sec;
+
/*
- * Calc the maximum number of seconds which we can run before
- * wrapping around. For clocksources which have a mask > 32bit
- * we need to limit the max sleep time to have a good
- * conversion precision. 10 minutes is still a reasonable
- * amount. That results in a shift value of 24 for a
- * clocksource with mask >= 40bit and f >= 4GHz. That maps to
- * ~ 0.06ppm granularity for NTP. We apply the same 12.5%
- * margin as we do in clocksource_max_deferment()
+ * Default clocksources are *special* and self-define their mult/shift.
+ * But, you're not special, so you should specify a freq value.
*/
- sec = (cs->mask - (cs->mask >> 3));
- do_div(sec, freq);
- do_div(sec, scale);
- if (!sec)
- sec = 1;
- else if (sec > 600 && cs->mask > UINT_MAX)
- sec = 600;
-
- clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
- NSEC_PER_SEC / scale, sec * scale);
-
+ if (freq) {
+ /*
+ * Calc the maximum number of seconds which we can run before
+ * wrapping around. For clocksources which have a mask > 32-bit
+ * we need to limit the max sleep time to have a good
+ * conversion precision. 10 minutes is still a reasonable
+ * amount. That results in a shift value of 24 for a
+ * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
+ * ~ 0.06ppm granularity for NTP.
+ */
+ sec = cs->mask;
+ do_div(sec, freq);
+ do_div(sec, scale);
+ if (!sec)
+ sec = 1;
+ else if (sec > 600 && cs->mask > UINT_MAX)
+ sec = 600;
+
+ clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
+ NSEC_PER_SEC / scale, sec * scale);
+ }
/*
- * for clocksources that have large mults, to avoid overflow.
- * Since mult may be adjusted by ntp, add an safety extra margin
- *
+ * Ensure clocksources that have large 'mult' values don't overflow
+ * when adjusted.
*/
cs->maxadj = clocksource_max_adjustment(cs);
- while ((cs->mult + cs->maxadj < cs->mult)
- || (cs->mult - cs->maxadj > cs->mult)) {
+ while (freq && ((cs->mult + cs->maxadj < cs->mult)
+ || (cs->mult - cs->maxadj > cs->mult))) {
cs->mult >>= 1;
cs->shift--;
cs->maxadj = clocksource_max_adjustment(cs);
}
- cs->max_idle_ns = clocksource_max_deferment(cs);
+ /*
+ * Only warn for *special* clocksources that self-define
+ * their mult/shift values and don't specify a freq.
+ */
+ WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
+ "timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
+ cs->name);
+
+ clocksource_update_max_deferment(cs);
}
EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
}
EXPORT_SYMBOL_GPL(__clocksource_register_scale);
-
-/**
- * clocksource_register - Used to install new clocksources
- * @cs: clocksource to be registered
- *
- * Returns -EBUSY if registration fails, zero otherwise.
- */
-int clocksource_register(struct clocksource *cs)
-{
- /* calculate max adjustment for given mult/shift */
- cs->maxadj = clocksource_max_adjustment(cs);
- WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
- "Clocksource %s might overflow on 11%% adjustment\n",
- cs->name);
-
- /* calculate max idle time permitted for this clocksource */
- cs->max_idle_ns = clocksource_max_deferment(cs);
-
- mutex_lock(&clocksource_mutex);
- clocksource_enqueue(cs);
- clocksource_enqueue_watchdog(cs);
- clocksource_select();
- mutex_unlock(&clocksource_mutex);
- return 0;
-}
-EXPORT_SYMBOL(clocksource_register);
-
static void __clocksource_change_rating(struct clocksource *cs, int rating)
{
list_del(&cs->list);
projects / karo-tx-linux.git / blobdiff