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 Ingo Molnar:
"This tree contains a clockevents regression fix for certain ARM
subarchitectures"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clockevents: Sanitize ticks to nsec conversion
+51
-16
+51
-16
kernel/time/clockevents.c
+51
-16
kernel/time/clockevents.c
···
33
33
int res;
34
34
};
35
35
36
+
static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
37
+
bool ismax)
38
+
{
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+
u64 clc = (u64) latch << evt->shift;
40
+
u64 rnd;
41
+
42
+
if (unlikely(!evt->mult)) {
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+
evt->mult = 1;
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+
WARN_ON(1);
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+
}
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+
rnd = (u64) evt->mult - 1;
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+
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+
/*
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+
* Upper bound sanity check. If the backwards conversion is
50
+
* not equal latch, we know that the above shift overflowed.
51
+
*/
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+
if ((clc >> evt->shift) != (u64)latch)
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+
clc = ~0ULL;
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+
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+
/*
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+
* Scaled math oddities:
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+
*
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+
* For mult <= (1 << shift) we can safely add mult - 1 to
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+
* prevent integer rounding loss. So the backwards conversion
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+
* from nsec to device ticks will be correct.
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+
*
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+
* For mult > (1 << shift), i.e. device frequency is > 1GHz we
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+
* need to be careful. Adding mult - 1 will result in a value
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+
* which when converted back to device ticks can be larger
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+
* than latch by up to (mult - 1) >> shift. For the min_delta
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+
* calculation we still want to apply this in order to stay
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+
* above the minimum device ticks limit. For the upper limit
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+
* we would end up with a latch value larger than the upper
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+
* limit of the device, so we omit the add to stay below the
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+
* device upper boundary.
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+
*
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+
* Also omit the add if it would overflow the u64 boundary.
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+
*/
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+
if ((~0ULL - clc > rnd) &&
75
+
(!ismax || evt->mult <= (1U << evt->shift)))
76
+
clc += rnd;
77
+
78
+
do_div(clc, evt->mult);
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+
80
+
/* Deltas less than 1usec are pointless noise */
81
+
return clc > 1000 ? clc : 1000;
82
+
}
83
+
36
84
/**
37
85
* clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
38
86
* @latch: value to convert
···
90
42
*/
91
43
u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
92
44
{
93
-
u64 clc = (u64) latch << evt->shift;
94
-
95
-
if (unlikely(!evt->mult)) {
96
-
evt->mult = 1;
97
-
WARN_ON(1);
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-
}
99
-
100
-
do_div(clc, evt->mult);
101
-
if (clc < 1000)
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-
clc = 1000;
103
-
if (clc > KTIME_MAX)
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-
clc = KTIME_MAX;
105
-
106
-
return clc;
45
+
return cev_delta2ns(latch, evt, false);
107
46
}
108
47
EXPORT_SYMBOL_GPL(clockevent_delta2ns);
109
48
···
415
380
sec = 600;
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381
417
382
clockevents_calc_mult_shift(dev, freq, sec);
418
-
dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
419
-
dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
383
+
dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
384
+
dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
420
385
}
421
386
422
387
/**