projects / lttng-modules.git / blame
| Commit | Line | Data |
|---|---|---|
| 9f36eaed MJ |
1 | /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1) |
| 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> | |
| 241ae9a8 MD |
14 | #include <lttng-events.h> |
| 15 | #include <wrapper/ringbuffer/frontend_types.h> | |
| 16 | #include <wrapper/vmalloc.h> | |
| 17 | #include <lttng-tracer.h> | |
| 79150a49 JD |
18 | |
| 19 | /* | |
| 20 | * We nest twice in preempt disabling within LTTng: one nesting is done | |
| 21 | * by the instrumentation (tracepoint, kprobes, kretprobes, syscall | |
| 22 | * tracepoint), and the second is within the lib ring buffer | |
| 23 | * lib_ring_buffer_get_cpu(). | |
| 24 | */ | |
| 25 | #define LTTNG_PREEMPT_DISABLE_NESTING 2 | |
| 26 | ||
| 27 | static | |
| 28 | size_t preemptible_get_size(size_t offset) | |
| 29 | { | |
| 30 | size_t size = 0; | |
| 31 | ||
| 32 | size += lib_ring_buffer_align(offset, lttng_alignof(uint8_t)); | |
| 33 | size += sizeof(uint8_t); | |
| 34 | return size; | |
| 35 | } | |
| 36 | ||
| 37 | static | |
| 38 | void preemptible_record(struct lttng_ctx_field *field, | |
| 39 | struct lib_ring_buffer_ctx *ctx, | |
| 40 | struct lttng_channel *chan) | |
| 41 | { | |
| 42 | int pc = preempt_count(); | |
| 43 | uint8_t preemptible = 0; | |
| 44 | ||
| 45 | WARN_ON_ONCE(pc < LTTNG_PREEMPT_DISABLE_NESTING); | |
| 46 | if (pc == LTTNG_PREEMPT_DISABLE_NESTING) | |
| 47 | preemptible = 1; | |
| 48 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(preemptible)); | |
| 49 | chan->ops->event_write(ctx, &preemptible, sizeof(preemptible)); | |
| 50 | } | |
| 51 | ||
| 52 | static | |
| 53 | void preemptible_get_value(struct lttng_ctx_field *field, | |
| 54 | struct lttng_probe_ctx *lttng_probe_ctx, | |
| 55 | union lttng_ctx_value *value) | |
| 56 | { | |
| 57 | int pc = preempt_count(); | |
| 58 | ||
| 59 | WARN_ON_ONCE(pc < LTTNG_PREEMPT_DISABLE_NESTING); | |
| 60 | if (pc == LTTNG_PREEMPT_DISABLE_NESTING) | |
| 61 | value->s64 = 1; | |
| 62 | else | |
| 63 | value->s64 = 0; | |
| 64 | } | |
| 65 | ||
| 66 | int lttng_add_preemptible_to_ctx(struct lttng_ctx **ctx) | |
| 67 | { | |
| 68 | struct lttng_ctx_field *field; | |
| 69 | ||
| 70 | field = lttng_append_context(ctx); | |
| 71 | if (!field) | |
| 72 | return -ENOMEM; | |
| 73 | if (lttng_find_context(*ctx, "preemptible")) { | |
| 74 | lttng_remove_context_field(ctx, field); | |
| 75 | return -EEXIST; | |
| 76 | } | |
| 77 | field->event_field.name = "preemptible"; | |
| 78 | field->event_field.type.atype = atype_integer; | |
| 79 | field->event_field.type.u.basic.integer.size = sizeof(uint8_t) * CHAR_BIT; | |
| 80 | field->event_field.type.u.basic.integer.alignment = lttng_alignof(uint8_t) * CHAR_BIT; | |
| 81 | field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(uint8_t); | |
| 82 | field->event_field.type.u.basic.integer.reverse_byte_order = 0; | |
| 83 | field->event_field.type.u.basic.integer.base = 10; | |
| 84 | field->event_field.type.u.basic.integer.encoding = lttng_encode_none; | |
| 85 | field->get_size = preemptible_get_size; | |
| 86 | field->record = preemptible_record; | |
| 87 | field->get_value = preemptible_get_value; | |
| 88 | lttng_context_update(*ctx); | |
| 89 | wrapper_vmalloc_sync_all(); | |
| 90 | return 0; | |
| 91 | } | |
| 92 | EXPORT_SYMBOL_GPL(lttng_add_preemptible_to_ctx); |