projects / deliverable / lttng-modules.git / blame
| Commit | Line | Data |
|---|---|---|
| 79150a49 JD |
1 | /* |
| 2 | * lttng-context-preemptible.c | |
| 3 | * | |
| 4 | * LTTng preemptible context. | |
| 5 | * | |
| 6 | * Copyright (C) 2009-2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
| 7 | * | |
| 8 | * This library is free software; you can redistribute it and/or | |
| 9 | * modify it under the terms of the GNU Lesser General Public | |
| 10 | * License as published by the Free Software Foundation; only | |
| 11 | * version 2.1 of the License. | |
| 12 | * | |
| 13 | * This library is distributed in the hope that it will be useful, | |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 16 | * Lesser General Public License for more details. | |
| 17 | * | |
| 18 | * You should have received a copy of the GNU Lesser General Public | |
| 19 | * License along with this library; if not, write to the Free Software | |
| 20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
| 21 | */ | |
| 22 | ||
| 23 | #include <linux/module.h> | |
| 24 | #include <linux/slab.h> | |
| 25 | #include <linux/sched.h> | |
| 26 | #include <linux/irqflags.h> | |
| 241ae9a8 MD |
27 | #include <lttng-events.h> |
| 28 | #include <wrapper/ringbuffer/frontend_types.h> | |
| 29 | #include <wrapper/vmalloc.h> | |
| 30 | #include <lttng-tracer.h> | |
| 79150a49 JD |
31 | |
| 32 | /* | |
| 33 | * We nest twice in preempt disabling within LTTng: one nesting is done | |
| 34 | * by the instrumentation (tracepoint, kprobes, kretprobes, syscall | |
| 35 | * tracepoint), and the second is within the lib ring buffer | |
| 36 | * lib_ring_buffer_get_cpu(). | |
| 37 | */ | |
| 38 | #define LTTNG_PREEMPT_DISABLE_NESTING 2 | |
| 39 | ||
| 40 | static | |
| 41 | size_t preemptible_get_size(size_t offset) | |
| 42 | { | |
| 43 | size_t size = 0; | |
| 44 | ||
| 45 | size += lib_ring_buffer_align(offset, lttng_alignof(uint8_t)); | |
| 46 | size += sizeof(uint8_t); | |
| 47 | return size; | |
| 48 | } | |
| 49 | ||
| 50 | static | |
| 51 | void preemptible_record(struct lttng_ctx_field *field, | |
| 52 | struct lib_ring_buffer_ctx *ctx, | |
| 53 | struct lttng_channel *chan) | |
| 54 | { | |
| 55 | int pc = preempt_count(); | |
| 56 | uint8_t preemptible = 0; | |
| 57 | ||
| 58 | WARN_ON_ONCE(pc < LTTNG_PREEMPT_DISABLE_NESTING); | |
| 59 | if (pc == LTTNG_PREEMPT_DISABLE_NESTING) | |
| 60 | preemptible = 1; | |
| 61 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(preemptible)); | |
| 62 | chan->ops->event_write(ctx, &preemptible, sizeof(preemptible)); | |
| 63 | } | |
| 64 | ||
| 65 | static | |
| 66 | void preemptible_get_value(struct lttng_ctx_field *field, | |
| 67 | struct lttng_probe_ctx *lttng_probe_ctx, | |
| 68 | union lttng_ctx_value *value) | |
| 69 | { | |
| 70 | int pc = preempt_count(); | |
| 71 | ||
| 72 | WARN_ON_ONCE(pc < LTTNG_PREEMPT_DISABLE_NESTING); | |
| 73 | if (pc == LTTNG_PREEMPT_DISABLE_NESTING) | |
| 74 | value->s64 = 1; | |
| 75 | else | |
| 76 | value->s64 = 0; | |
| 77 | } | |
| 78 | ||
| 79 | int lttng_add_preemptible_to_ctx(struct lttng_ctx **ctx) | |
| 80 | { | |
| 81 | struct lttng_ctx_field *field; | |
| 82 | ||
| 83 | field = lttng_append_context(ctx); | |
| 84 | if (!field) | |
| 85 | return -ENOMEM; | |
| 86 | if (lttng_find_context(*ctx, "preemptible")) { | |
| 87 | lttng_remove_context_field(ctx, field); | |
| 88 | return -EEXIST; | |
| 89 | } | |
| 90 | field->event_field.name = "preemptible"; | |
| 91 | field->event_field.type.atype = atype_integer; | |
| 92 | field->event_field.type.u.basic.integer.size = sizeof(uint8_t) * CHAR_BIT; | |
| 93 | field->event_field.type.u.basic.integer.alignment = lttng_alignof(uint8_t) * CHAR_BIT; | |
| 94 | field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(uint8_t); | |
| 95 | field->event_field.type.u.basic.integer.reverse_byte_order = 0; | |
| 96 | field->event_field.type.u.basic.integer.base = 10; | |
| 97 | field->event_field.type.u.basic.integer.encoding = lttng_encode_none; | |
| 98 | field->get_size = preemptible_get_size; | |
| 99 | field->record = preemptible_record; | |
| 100 | field->get_value = preemptible_get_value; | |
| 101 | lttng_context_update(*ctx); | |
| 102 | wrapper_vmalloc_sync_all(); | |
| 103 | return 0; | |
| 104 | } | |
| 105 | EXPORT_SYMBOL_GPL(lttng_add_preemptible_to_ctx); |