[lttng-modules.git] / src / lttng-context-preemptible.c

/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
 *
 * lttng-context-preemptible.c
 *
 * LTTng preemptible context.
 *
 * Copyright (C) 2009-2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/irqflags.h>
#include <lttng/events.h>
#include <lttng/events-internal.h>
#include <ringbuffer/frontend_types.h>
#include <wrapper/vmalloc.h>
#include <lttng/tracer.h>

/*
 * We nest twice in preempt disabling within LTTng: one nesting is done
 * by the instrumentation (tracepoint, kprobes, kretprobes, syscall
 * tracepoint), and the second is within the lib ring buffer
 * lib_ring_buffer_get_cpu().
 */
#define LTTNG_PREEMPT_DISABLE_NESTING	2

static
size_t preemptible_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
{
	size_t size = 0;

	size += lib_ring_buffer_align(offset, lttng_alignof(uint8_t));
	size += sizeof(uint8_t);
	return size;
}

static
void preemptible_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
		struct lttng_kernel_ring_buffer_ctx *ctx,
		struct lttng_channel *chan)
{
	int pc = preempt_count();
	uint8_t preemptible = 0;

	WARN_ON_ONCE(pc < LTTNG_PREEMPT_DISABLE_NESTING);
	if (pc == LTTNG_PREEMPT_DISABLE_NESTING)
		preemptible = 1;
	lib_ring_buffer_align_ctx(ctx, lttng_alignof(preemptible));
	chan->ops->event_write(ctx, &preemptible, sizeof(preemptible));
}

static
void preemptible_get_value(void *priv,
		struct lttng_kernel_probe_ctx *lttng_probe_ctx,
		struct lttng_ctx_value *value)
{
	int pc = preempt_count();

	WARN_ON_ONCE(pc < LTTNG_PREEMPT_DISABLE_NESTING);
	if (pc == LTTNG_PREEMPT_DISABLE_NESTING)
		value->u.s64 = 1;
	else
		value->u.s64 = 0;
}

static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
	lttng_kernel_static_event_field("preemptible",
		lttng_kernel_static_type_integer_from_type(uint8_t, __BYTE_ORDER, 10),
		false, false, false),
	preemptible_get_size,
	preemptible_record,
	preemptible_get_value,
	NULL, NULL);

int lttng_add_preemptible_to_ctx(struct lttng_kernel_ctx **ctx)
{
	int ret;

	if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
		return -EEXIST;
	ret = lttng_kernel_context_append(ctx, ctx_field);
	wrapper_vmalloc_sync_mappings();
	return ret;
}
EXPORT_SYMBOL_GPL(lttng_add_preemptible_to_ctx);
Commit	Line	Data
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>
0fe45627	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
a92e844e	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
a92e844e	39	void preemptible_record(void priv, struct lttng_kernel_probe_ctx probe_ctx,
8a57ec02	40	struct lttng_kernel_ring_buffer_ctx *ctx,
79150a49 JD	41	struct lttng_channel *chan)
	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
bf99c737	54	void preemptible_get_value(void *priv,
a92e844e	55	struct lttng_kernel_probe_ctx *lttng_probe_ctx,
bf99c737	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)
bf99c737	62	value->u.s64 = 1;
79150a49	63	else
bf99c737	64	value->u.s64 = 0;
79150a49 JD	65	}
79150a49 JD	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	}
79150a49 JD	86	EXPORT_SYMBOL_GPL(lttng_add_preemptible_to_ctx);