Commit | Line | Data |
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5d1638ac PM |
1 | /* |
2 | * linux/kernel/time/tick-broadcast-hrtimer.c | |
3 | * This file emulates a local clock event device | |
4 | * via a pseudo clock device. | |
5 | */ | |
6 | #include <linux/cpu.h> | |
7 | #include <linux/err.h> | |
8 | #include <linux/hrtimer.h> | |
9 | #include <linux/interrupt.h> | |
10 | #include <linux/percpu.h> | |
11 | #include <linux/profile.h> | |
12 | #include <linux/clockchips.h> | |
13 | #include <linux/sched.h> | |
14 | #include <linux/smp.h> | |
15 | #include <linux/module.h> | |
16 | ||
17 | #include "tick-internal.h" | |
18 | ||
19 | static struct hrtimer bctimer; | |
20 | ||
21 | static void bc_set_mode(enum clock_event_mode mode, | |
22 | struct clock_event_device *bc) | |
23 | { | |
24 | switch (mode) { | |
38d23a6c | 25 | case CLOCK_EVT_MODE_UNUSED: |
5d1638ac PM |
26 | case CLOCK_EVT_MODE_SHUTDOWN: |
27 | /* | |
28 | * Note, we cannot cancel the timer here as we might | |
29 | * run into the following live lock scenario: | |
30 | * | |
31 | * cpu 0 cpu1 | |
32 | * lock(broadcast_lock); | |
33 | * hrtimer_interrupt() | |
34 | * bc_handler() | |
35 | * tick_handle_oneshot_broadcast(); | |
36 | * lock(broadcast_lock); | |
37 | * hrtimer_cancel() | |
38 | * wait_for_callback() | |
39 | */ | |
40 | hrtimer_try_to_cancel(&bctimer); | |
41 | break; | |
42 | default: | |
43 | break; | |
44 | } | |
45 | } | |
46 | ||
47 | /* | |
48 | * This is called from the guts of the broadcast code when the cpu | |
49 | * which is about to enter idle has the earliest broadcast timer event. | |
50 | */ | |
51 | static int bc_set_next(ktime_t expires, struct clock_event_device *bc) | |
52 | { | |
a127d2bc | 53 | int bc_moved; |
5d1638ac PM |
54 | /* |
55 | * We try to cancel the timer first. If the callback is on | |
56 | * flight on some other cpu then we let it handle it. If we | |
57 | * were able to cancel the timer nothing can rearm it as we | |
58 | * own broadcast_lock. | |
59 | * | |
60 | * However we can also be called from the event handler of | |
61 | * ce_broadcast_hrtimer itself when it expires. We cannot | |
62 | * restart the timer because we are in the callback, but we | |
63 | * can set the expiry time and let the callback return | |
64 | * HRTIMER_RESTART. | |
a127d2bc PM |
65 | * |
66 | * Since we are in the idle loop at this point and because | |
67 | * hrtimer_{start/cancel} functions call into tracing, | |
68 | * calls to these functions must be bound within RCU_NONIDLE. | |
5d1638ac | 69 | */ |
b8a62f1f TG |
70 | RCU_NONIDLE({ |
71 | bc_moved = hrtimer_try_to_cancel(&bctimer) >= 0; | |
72 | if (bc_moved) | |
73 | hrtimer_start(&bctimer, expires, | |
74 | HRTIMER_MODE_ABS_PINNED);}); | |
a127d2bc | 75 | if (bc_moved) { |
5d1638ac PM |
76 | /* Bind the "device" to the cpu */ |
77 | bc->bound_on = smp_processor_id(); | |
78 | } else if (bc->bound_on == smp_processor_id()) { | |
79 | hrtimer_set_expires(&bctimer, expires); | |
80 | } | |
81 | return 0; | |
82 | } | |
83 | ||
84 | static struct clock_event_device ce_broadcast_hrtimer = { | |
85 | .set_mode = bc_set_mode, | |
86 | .set_next_ktime = bc_set_next, | |
87 | .features = CLOCK_EVT_FEAT_ONESHOT | | |
88 | CLOCK_EVT_FEAT_KTIME | | |
89 | CLOCK_EVT_FEAT_HRTIMER, | |
90 | .rating = 0, | |
91 | .bound_on = -1, | |
92 | .min_delta_ns = 1, | |
93 | .max_delta_ns = KTIME_MAX, | |
94 | .min_delta_ticks = 1, | |
849401b6 | 95 | .max_delta_ticks = ULONG_MAX, |
5d1638ac PM |
96 | .mult = 1, |
97 | .shift = 0, | |
98 | .cpumask = cpu_all_mask, | |
99 | }; | |
100 | ||
101 | static enum hrtimer_restart bc_handler(struct hrtimer *t) | |
102 | { | |
103 | ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer); | |
104 | ||
38d23a6c AS |
105 | switch (ce_broadcast_hrtimer.mode) { |
106 | case CLOCK_EVT_MODE_ONESHOT: | |
107 | if (ce_broadcast_hrtimer.next_event.tv64 != KTIME_MAX) | |
108 | return HRTIMER_RESTART; | |
109 | default: | |
5d1638ac | 110 | return HRTIMER_NORESTART; |
38d23a6c | 111 | } |
5d1638ac PM |
112 | } |
113 | ||
114 | void tick_setup_hrtimer_broadcast(void) | |
115 | { | |
116 | hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
117 | bctimer.function = bc_handler; | |
118 | clockevents_register_device(&ce_broadcast_hrtimer); | |
119 | } |