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

/*
 * lttng-context-preemptible.c
 *
 * LTTng preemptible context.
 *
 * Copyright (C) 2009-2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; only
 * version 2.1 of the License.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/irqflags.h>
#include <lttng-events.h>
#include <wrapper/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(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(struct lttng_ctx_field *field,
		struct lib_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(struct lttng_ctx_field *field,
		struct lttng_probe_ctx *lttng_probe_ctx,
		union lttng_ctx_value *value)
{
	int pc = preempt_count();

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

int lttng_add_preemptible_to_ctx(struct lttng_ctx **ctx)
{
	struct lttng_ctx_field *field;

	field = lttng_append_context(ctx);
	if (!field)
		return -ENOMEM;
	if (lttng_find_context(*ctx, "preemptible")) {
		lttng_remove_context_field(ctx, field);
		return -EEXIST;
	}
	field->event_field.name = "preemptible";
	field->event_field.type.atype = atype_integer;
	field->event_field.type.u.basic.integer.size = sizeof(uint8_t) * CHAR_BIT;
	field->event_field.type.u.basic.integer.alignment = lttng_alignof(uint8_t) * CHAR_BIT;
	field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(uint8_t);
	field->event_field.type.u.basic.integer.reverse_byte_order = 0;
	field->event_field.type.u.basic.integer.base = 10;
	field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
	field->get_size = preemptible_get_size;
	field->record = preemptible_record;
	field->get_value = preemptible_get_value;
	lttng_context_update(*ctx);
	wrapper_vmalloc_sync_all();
	return 0;
}
EXPORT_SYMBOL_GPL(lttng_add_preemptible_to_ctx);
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);