Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Thomas Gleixner:
"Serialize the registration of a new sched_clock in the currently ARM
only generic sched_clock facilty to avoid sched_clock havoc"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched_clock: Prevent callers from seeing half-updated data
+29
-17
+29
-17
kernel/time/sched_clock.c
+29
-17
kernel/time/sched_clock.c
···
116
116
void __init sched_clock_register(u64 (*read)(void), int bits,
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117
unsigned long rate)
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{
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+
u64 res, wrap, new_mask, new_epoch, cyc, ns;
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+
u32 new_mult, new_shift;
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+
ktime_t new_wrap_kt;
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unsigned long r;
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-
u64 res, wrap;
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char r_unit;
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if (cd.rate > rate)
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return;
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WARN_ON(!irqs_disabled());
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-
read_sched_clock = read;
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-
sched_clock_mask = CLOCKSOURCE_MASK(bits);
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-
cd.rate = rate;
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/* calculate the mult/shift to convert counter ticks to ns. */
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-
clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 3600);
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+
clocks_calc_mult_shift(&new_mult, &new_shift, rate, NSEC_PER_SEC, 3600);
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+
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+
new_mask = CLOCKSOURCE_MASK(bits);
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+
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+
/* calculate how many ns until we wrap */
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+
wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask);
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+
new_wrap_kt = ns_to_ktime(wrap - (wrap >> 3));
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+
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+
/* update epoch for new counter and update epoch_ns from old counter*/
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+
new_epoch = read();
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+
cyc = read_sched_clock();
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+
ns = cd.epoch_ns + cyc_to_ns((cyc - cd.epoch_cyc) & sched_clock_mask,
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+
cd.mult, cd.shift);
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+
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+
raw_write_seqcount_begin(&cd.seq);
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+
read_sched_clock = read;
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+
sched_clock_mask = new_mask;
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+
cd.rate = rate;
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+
cd.wrap_kt = new_wrap_kt;
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+
cd.mult = new_mult;
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+
cd.shift = new_shift;
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+
cd.epoch_cyc = new_epoch;
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+
cd.epoch_ns = ns;
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+
raw_write_seqcount_end(&cd.seq);
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r = rate;
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if (r >= 4000000) {
···
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141
} else
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r_unit = ' ';
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143
166
-
/* calculate how many ns until we wrap */
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-
wrap = clocks_calc_max_nsecs(cd.mult, cd.shift, 0, sched_clock_mask);
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-
cd.wrap_kt = ns_to_ktime(wrap - (wrap >> 3));
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-
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/* calculate the ns resolution of this counter */
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-
res = cyc_to_ns(1ULL, cd.mult, cd.shift);
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+
res = cyc_to_ns(1ULL, new_mult, new_shift);
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+
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pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lluns\n",
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bits, r, r_unit, res, wrap);
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-
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-
update_sched_clock();
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-
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-
/*
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-
* Ensure that sched_clock() starts off at 0ns
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-
*/
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-
cd.epoch_ns = 0;
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149
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/* Enable IRQ time accounting if we have a fast enough sched_clock */
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if (irqtime > 0 || (irqtime == -1 && rate >= 1000000))