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b7cdc182 | 1 | /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) |
9f36eaed | 2 | * |
79150a49 JD |
3 | * lttng-context-preemptible.c |
4 | * | |
5 | * LTTng preemptible context. | |
6 | * | |
7 | * Copyright (C) 2009-2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
79150a49 JD |
8 | */ |
9 | ||
10 | #include <linux/module.h> | |
11 | #include <linux/slab.h> | |
12 | #include <linux/sched.h> | |
13 | #include <linux/irqflags.h> | |
2df37e95 | 14 | #include <lttng/events.h> |
7207017d | 15 | #include <lttng/events-internal.h> |
24591303 | 16 | #include <ringbuffer/frontend_types.h> |
241ae9a8 | 17 | #include <wrapper/vmalloc.h> |
2df37e95 | 18 | #include <lttng/tracer.h> |
79150a49 JD |
19 | |
20 | /* | |
21 | * We nest twice in preempt disabling within LTTng: one nesting is done | |
22 | * by the instrumentation (tracepoint, kprobes, kretprobes, syscall | |
23 | * tracepoint), and the second is within the lib ring buffer | |
24 | * lib_ring_buffer_get_cpu(). | |
25 | */ | |
26 | #define LTTNG_PREEMPT_DISABLE_NESTING 2 | |
27 | ||
28 | static | |
346cb5ee | 29 | size_t preemptible_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset) |
79150a49 JD |
30 | { |
31 | size_t size = 0; | |
32 | ||
33 | size += lib_ring_buffer_align(offset, lttng_alignof(uint8_t)); | |
34 | size += sizeof(uint8_t); | |
35 | return size; | |
36 | } | |
37 | ||
38 | static | |
346cb5ee | 39 | void preemptible_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, |
e27e4381 | 40 | struct lttng_kernel_ring_buffer_ctx *ctx, |
ac847066 | 41 | struct lttng_kernel_channel_buffer *chan) |
79150a49 JD |
42 | { |
43 | int pc = preempt_count(); | |
44 | uint8_t preemptible = 0; | |
45 | ||
46 | WARN_ON_ONCE(pc < LTTNG_PREEMPT_DISABLE_NESTING); | |
47 | if (pc == LTTNG_PREEMPT_DISABLE_NESTING) | |
48 | preemptible = 1; | |
49 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(preemptible)); | |
50 | chan->ops->event_write(ctx, &preemptible, sizeof(preemptible)); | |
51 | } | |
52 | ||
53 | static | |
a73e5368 | 54 | void preemptible_get_value(void *priv, |
346cb5ee | 55 | struct lttng_kernel_probe_ctx *lttng_probe_ctx, |
a73e5368 | 56 | struct lttng_ctx_value *value) |
79150a49 JD |
57 | { |
58 | int pc = preempt_count(); | |
59 | ||
60 | WARN_ON_ONCE(pc < LTTNG_PREEMPT_DISABLE_NESTING); | |
61 | if (pc == LTTNG_PREEMPT_DISABLE_NESTING) | |
a73e5368 | 62 | value->u.s64 = 1; |
79150a49 | 63 | else |
a73e5368 | 64 | value->u.s64 = 0; |
79150a49 JD |
65 | } |
66 | ||
087e3f1b MJ |
67 | static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field( |
68 | lttng_kernel_static_event_field("preemptible", | |
69 | lttng_kernel_static_type_integer_from_type(uint8_t, __BYTE_ORDER, 10), | |
70 | false, false, false), | |
71 | preemptible_get_size, | |
087e3f1b MJ |
72 | preemptible_record, |
73 | preemptible_get_value, | |
74 | NULL, NULL); | |
75 | ||
437d5aa5 | 76 | int lttng_add_preemptible_to_ctx(struct lttng_kernel_ctx **ctx) |
79150a49 | 77 | { |
087e3f1b | 78 | int ret; |
79150a49 | 79 | |
087e3f1b | 80 | if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name)) |
79150a49 | 81 | return -EEXIST; |
087e3f1b | 82 | ret = lttng_kernel_context_append(ctx, ctx_field); |
263b6c88 | 83 | wrapper_vmalloc_sync_mappings(); |
087e3f1b | 84 | return ret; |
79150a49 JD |
85 | } |
86 | EXPORT_SYMBOL_GPL(lttng_add_preemptible_to_ctx); |