Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge tag 'timers_urgent_for_v6.13_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Borislav Petkov:
- Handle the case where clocksources with small counter width can,
in conjunction with overly long idle sleeps, falsely trigger the
negative motion detection of clocksources
* tag 'timers_urgent_for_v6.13_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clocksource: Make negative motion detection more robust
+20
-7
+2
include/linux/clocksource.h
+2
include/linux/clocksource.h
···
49
49
* @archdata: Optional arch-specific data
50
50
* @max_cycles: Maximum safe cycle value which won't overflow on
51
51
* multiplication
52
+
* @max_raw_delta: Maximum safe delta value for negative motion detection
52
53
* @name: Pointer to clocksource name
53
54
* @list: List head for registration (internal)
54
55
* @freq_khz: Clocksource frequency in khz.
···
110
109
struct arch_clocksource_data archdata;
111
110
#endif
112
111
u64 max_cycles;
112
+
u64 max_raw_delta;
113
113
const char *name;
114
114
struct list_head list;
115
115
u32 freq_khz;
+10
-1
kernel/time/clocksource.c
+10
-1
kernel/time/clocksource.c
···
24
24
25
25
static noinline u64 cycles_to_nsec_safe(struct clocksource *cs, u64 start, u64 end)
26
26
{
27
-
u64 delta = clocksource_delta(end, start, cs->mask);
27
+
u64 delta = clocksource_delta(end, start, cs->mask, cs->max_raw_delta);
28
28
29
29
if (likely(delta < cs->max_cycles))
30
30
return clocksource_cyc2ns(delta, cs->mult, cs->shift);
···
993
993
cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
994
994
cs->maxadj, cs->mask,
995
995
&cs->max_cycles);
996
+
997
+
/*
998
+
* Threshold for detecting negative motion in clocksource_delta().
999
+
*
1000
+
* Allow for 0.875 of the counter width so that overly long idle
1001
+
* sleeps, which go slightly over mask/2, do not trigger the
1002
+
* negative motion detection.
1003
+
*/
1004
+
cs->max_raw_delta = (cs->mask >> 1) + (cs->mask >> 2) + (cs->mask >> 3);
996
1005
}
997
1006
998
1007
static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
+4
-2
kernel/time/timekeeping.c
+4
-2
kernel/time/timekeeping.c
···
755
755
u64 cycle_now, delta;
756
756
757
757
cycle_now = tk_clock_read(&tk->tkr_mono);
758
-
delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
758
+
delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask,
759
+
tk->tkr_mono.clock->max_raw_delta);
759
760
tk->tkr_mono.cycle_last = cycle_now;
760
761
tk->tkr_raw.cycle_last = cycle_now;
761
762
···
2231
2230
return false;
2232
2231
2233
2232
offset = clocksource_delta(tk_clock_read(&tk->tkr_mono),
2234
-
tk->tkr_mono.cycle_last, tk->tkr_mono.mask);
2233
+
tk->tkr_mono.cycle_last, tk->tkr_mono.mask,
2234
+
tk->tkr_mono.clock->max_raw_delta);
2235
2235
2236
2236
/* Check if there's really nothing to do */
2237
2237
if (offset < real_tk->cycle_interval && mode == TK_ADV_TICK)
+4
-4
kernel/time/timekeeping_internal.h
+4
-4
kernel/time/timekeeping_internal.h
···
30
30
31
31
#endif
32
32
33
-
static inline u64 clocksource_delta(u64 now, u64 last, u64 mask)
33
+
static inline u64 clocksource_delta(u64 now, u64 last, u64 mask, u64 max_delta)
34
34
{
35
35
u64 ret = (now - last) & mask;
36
36
37
37
/*
38
-
* Prevent time going backwards by checking the MSB of mask in
39
-
* the result. If set, return 0.
38
+
* Prevent time going backwards by checking the result against
39
+
* @max_delta. If greater, return 0.
40
40
*/
41
-
return ret & ~(mask >> 1) ? 0 : ret;
41
+
return ret > max_delta ? 0 : ret;
42
42
}
43
43
44
44
/* Semi public for serialization of non timekeeper VDSO updates. */