[mirror_ubuntu-bionic-kernel.git] / drivers / oprofile / cpu_buffer.c

/**
 * @file cpu_buffer.c
 *
 * @remark Copyright 2002 OProfile authors
 * @remark Read the file COPYING
 *
 * @author John Levon <levon@movementarian.org>
 * @author Barry Kasindorf <barry.kasindorf@amd.com>
 *
 * Each CPU has a local buffer that stores PC value/event
 * pairs. We also log context switches when we notice them.
 * Eventually each CPU's buffer is processed into the global
 * event buffer by sync_buffer().
 *
 * We use a local buffer for two reasons: an NMI or similar
 * interrupt cannot synchronise, and high sampling rates
 * would lead to catastrophic global synchronisation if
 * a global buffer was used.
 */

#include <linux/sched.h>
#include <linux/oprofile.h>
#include <linux/vmalloc.h>
#include <linux/errno.h>
 
#include "event_buffer.h"
#include "cpu_buffer.h"
#include "buffer_sync.h"
#include "oprof.h"

DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);

static void wq_sync_buffer(struct work_struct *work);

#define DEFAULT_TIMER_EXPIRE (HZ / 10)
static int work_enabled;

void free_cpu_buffers(void)
{
	int i;
 
	for_each_online_cpu(i)
		vfree(per_cpu(cpu_buffer, i).buffer);
}

int alloc_cpu_buffers(void)
{
	int i;
 
	unsigned long buffer_size = fs_cpu_buffer_size;
 
	for_each_online_cpu(i) {
		struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
 
		b->buffer = vmalloc_node(sizeof(struct op_sample) * buffer_size,
			cpu_to_node(i));
		if (!b->buffer)
			goto fail;
 
		b->last_task = NULL;
		b->last_is_kernel = -1;
		b->tracing = 0;
		b->buffer_size = buffer_size;
		b->tail_pos = 0;
		b->head_pos = 0;
		b->sample_received = 0;
		b->sample_lost_overflow = 0;
		b->backtrace_aborted = 0;
		b->sample_invalid_eip = 0;
		b->cpu = i;
		INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
	}
	return 0;

fail:
	free_cpu_buffers();
	return -ENOMEM;
}

void start_cpu_work(void)
{
	int i;

	work_enabled = 1;

	for_each_online_cpu(i) {
		struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);

		/*
		 * Spread the work by 1 jiffy per cpu so they dont all
		 * fire at once.
		 */
		schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
	}
}

void end_cpu_work(void)
{
	int i;

	work_enabled = 0;

	for_each_online_cpu(i) {
		struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);

		cancel_delayed_work(&b->work);
	}

	flush_scheduled_work();
}

/* Resets the cpu buffer to a sane state. */
void cpu_buffer_reset(struct oprofile_cpu_buffer * cpu_buf)
{
	/* reset these to invalid values; the next sample
	 * collected will populate the buffer with proper
	 * values to initialize the buffer
	 */
	cpu_buf->last_is_kernel = -1;
	cpu_buf->last_task = NULL;
}

/* compute number of available slots in cpu_buffer queue */
static unsigned long nr_available_slots(struct oprofile_cpu_buffer const * b)
{
	unsigned long head = b->head_pos;
	unsigned long tail = b->tail_pos;

	if (tail > head)
		return (tail - head) - 1;

	return tail + (b->buffer_size - head) - 1;
}

static void increment_head(struct oprofile_cpu_buffer * b)
{
	unsigned long new_head = b->head_pos + 1;

	/* Ensure anything written to the slot before we
	 * increment is visible */
	wmb();

	if (new_head < b->buffer_size)
		b->head_pos = new_head;
	else
		b->head_pos = 0;
}

static inline void
add_sample(struct oprofile_cpu_buffer * cpu_buf,
           unsigned long pc, unsigned long event)
{
	struct op_sample * entry = &cpu_buf->buffer[cpu_buf->head_pos];
	entry->eip = pc;
	entry->event = event;
	increment_head(cpu_buf);
}

static inline void
add_code(struct oprofile_cpu_buffer * buffer, unsigned long value)
{
	add_sample(buffer, ESCAPE_CODE, value);
}

/* This must be safe from any context. It's safe writing here
 * because of the head/tail separation of the writer and reader
 * of the CPU buffer.
 *
 * is_kernel is needed because on some architectures you cannot
 * tell if you are in kernel or user space simply by looking at
 * pc. We tag this in the buffer by generating kernel enter/exit
 * events whenever is_kernel changes
 */
static int log_sample(struct oprofile_cpu_buffer * cpu_buf, unsigned long pc,
		      int is_kernel, unsigned long event)
{
	struct task_struct * task;

	cpu_buf->sample_received++;

	if (pc == ESCAPE_CODE) {
		cpu_buf->sample_invalid_eip++;
		return 0;
	}

	if (nr_available_slots(cpu_buf) < 3) {
		cpu_buf->sample_lost_overflow++;
		return 0;
	}

	is_kernel = !!is_kernel;

	task = current;

	/* notice a switch from user->kernel or vice versa */
	if (cpu_buf->last_is_kernel != is_kernel) {
		cpu_buf->last_is_kernel = is_kernel;
		add_code(cpu_buf, is_kernel);
	}

	/* notice a task switch */
	if (cpu_buf->last_task != task) {
		cpu_buf->last_task = task;
		add_code(cpu_buf, (unsigned long)task);
	}
 
	add_sample(cpu_buf, pc, event);
	return 1;
}

static int oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
{
	if (nr_available_slots(cpu_buf) < 4) {
		cpu_buf->sample_lost_overflow++;
		return 0;
	}

	add_code(cpu_buf, CPU_TRACE_BEGIN);
	cpu_buf->tracing = 1;
	return 1;
}

static void oprofile_end_trace(struct oprofile_cpu_buffer * cpu_buf)
{
	cpu_buf->tracing = 0;
}

void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
				unsigned long event, int is_kernel)
{
	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);

	if (!backtrace_depth) {
		log_sample(cpu_buf, pc, is_kernel, event);
		return;
	}

	if (!oprofile_begin_trace(cpu_buf))
		return;

	/* if log_sample() fail we can't backtrace since we lost the source
	 * of this event */
	if (log_sample(cpu_buf, pc, is_kernel, event))
		oprofile_ops.backtrace(regs, backtrace_depth);
	oprofile_end_trace(cpu_buf);
}

void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
{
	int is_kernel = !user_mode(regs);
	unsigned long pc = profile_pc(regs);

	oprofile_add_ext_sample(pc, regs, event, is_kernel);
}

#define MAX_IBS_SAMPLE_SIZE	14
static int log_ibs_sample(struct oprofile_cpu_buffer *cpu_buf,
	unsigned long pc, int is_kernel, unsigned  int *ibs, int ibs_code)
{
	struct task_struct *task;

	cpu_buf->sample_received++;

	if (nr_available_slots(cpu_buf) < MAX_IBS_SAMPLE_SIZE) {
		cpu_buf->sample_lost_overflow++;
		return 0;
	}

	is_kernel = !!is_kernel;

	/* notice a switch from user->kernel or vice versa */
	if (cpu_buf->last_is_kernel != is_kernel) {
		cpu_buf->last_is_kernel = is_kernel;
		add_code(cpu_buf, is_kernel);
	}

	/* notice a task switch */
	if (!is_kernel) {
		task = current;

		if (cpu_buf->last_task != task) {
			cpu_buf->last_task = task;
			add_code(cpu_buf, (unsigned long)task);
		}
	}

	add_code(cpu_buf, ibs_code);
	add_sample(cpu_buf, ibs[0], ibs[1]);
	add_sample(cpu_buf, ibs[2], ibs[3]);
	add_sample(cpu_buf, ibs[4], ibs[5]);

	if (ibs_code == IBS_OP_BEGIN) {
	add_sample(cpu_buf, ibs[6], ibs[7]);
	add_sample(cpu_buf, ibs[8], ibs[9]);
	add_sample(cpu_buf, ibs[10], ibs[11]);
	}

	return 1;
}

void oprofile_add_ibs_sample(struct pt_regs *const regs,
				unsigned int * const ibs_sample, u8 code)
{
	int is_kernel = !user_mode(regs);
	unsigned long pc = profile_pc(regs);

	struct oprofile_cpu_buffer *cpu_buf =
			 &per_cpu(cpu_buffer, smp_processor_id());

	if (!backtrace_depth) {
		log_ibs_sample(cpu_buf, pc, is_kernel, ibs_sample, code);
		return;
	}

	/* if log_sample() fails we can't backtrace since we lost the source
	* of this event */
	if (log_ibs_sample(cpu_buf, pc, is_kernel, ibs_sample, code))
		oprofile_ops.backtrace(regs, backtrace_depth);
}

void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
{
	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
	log_sample(cpu_buf, pc, is_kernel, event);
}

void oprofile_add_trace(unsigned long pc)
{
	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);

	if (!cpu_buf->tracing)
		return;

	if (nr_available_slots(cpu_buf) < 1) {
		cpu_buf->tracing = 0;
		cpu_buf->sample_lost_overflow++;
		return;
	}

	/* broken frame can give an eip with the same value as an escape code,
	 * abort the trace if we get it */
	if (pc == ESCAPE_CODE) {
		cpu_buf->tracing = 0;
		cpu_buf->backtrace_aborted++;
		return;
	}

	add_sample(cpu_buf, pc, 0);
}

/*
 * This serves to avoid cpu buffer overflow, and makes sure
 * the task mortuary progresses
 *
 * By using schedule_delayed_work_on and then schedule_delayed_work
 * we guarantee this will stay on the correct cpu
 */
static void wq_sync_buffer(struct work_struct *work)
{
	struct oprofile_cpu_buffer * b =
		container_of(work, struct oprofile_cpu_buffer, work.work);
	if (b->cpu != smp_processor_id()) {
		printk("WQ on CPU%d, prefer CPU%d\n",
		       smp_processor_id(), b->cpu);
	}
	sync_buffer(b->cpu);

	/* don't re-add the work if we're shutting down */
	if (work_enabled)
		schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
}
Commit	Line	Data
1da177e4 LT	1	/**
	2	* @file cpu_buffer.c
	3	*
	4	* @remark Copyright 2002 OProfile authors
	5	* @remark Read the file COPYING
	6	*
	7	* @author John Levon <levon@movementarian.org>
345c2573	8	* @author Barry Kasindorf <barry.kasindorf@amd.com>
1da177e4 LT	9	*
	10	* Each CPU has a local buffer that stores PC value/event
	11	* pairs. We also log context switches when we notice them.
	12	* Eventually each CPU's buffer is processed into the global
	13	* event buffer by sync_buffer().
	14	*
	15	* We use a local buffer for two reasons: an NMI or similar
	16	* interrupt cannot synchronise, and high sampling rates
	17	* would lead to catastrophic global synchronisation if
	18	* a global buffer was used.
	19	*/
	20
	21	#include <linux/sched.h>
	22	#include <linux/oprofile.h>
	23	#include <linux/vmalloc.h>
	24	#include <linux/errno.h>
	25
	26	#include "event_buffer.h"
	27	#include "cpu_buffer.h"
	28	#include "buffer_sync.h"
	29	#include "oprof.h"
	30
8b8b4988	31	DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
1da177e4	32
c4028958	33	static void wq_sync_buffer(struct work_struct *work);
1da177e4 LT	34
	35	#define DEFAULT_TIMER_EXPIRE (HZ / 10)
	36	static int work_enabled;
	37
	38	void free_cpu_buffers(void)
	39	{
	40	int i;
	41
394e3902	42	for_each_online_cpu(i)
608dfddd	43	vfree(per_cpu(cpu_buffer, i).buffer);
1da177e4	44	}
77933d72	45
1da177e4 LT	46	int alloc_cpu_buffers(void)
	47	{
	48	int i;
	49
	50	unsigned long buffer_size = fs_cpu_buffer_size;
	51
	52	for_each_online_cpu(i) {
608dfddd	53	struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
1da177e4	54
25ab7cd8 ED	55	b->buffer = vmalloc_node(sizeof(struct op_sample) * buffer_size,
25ab7cd8 ED	56	cpu_to_node(i));
1da177e4 LT	57	if (!b->buffer)
	58	goto fail;
	59
	60	b->last_task = NULL;
	61	b->last_is_kernel = -1;
	62	b->tracing = 0;
	63	b->buffer_size = buffer_size;
	64	b->tail_pos = 0;
	65	b->head_pos = 0;
	66	b->sample_received = 0;
	67	b->sample_lost_overflow = 0;
df9d177a PE	68	b->backtrace_aborted = 0;
df9d177a PE	69	b->sample_invalid_eip = 0;
1da177e4	70	b->cpu = i;
c4028958	71	INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
1da177e4 LT	72	}
	73	return 0;
	74
	75	fail:
	76	free_cpu_buffers();
	77	return -ENOMEM;
	78	}
1da177e4 LT	79
	80	void start_cpu_work(void)
	81	{
	82	int i;
	83
	84	work_enabled = 1;
	85
	86	for_each_online_cpu(i) {
608dfddd	87	struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
1da177e4 LT	88
	89	/*
	90	* Spread the work by 1 jiffy per cpu so they dont all
	91	* fire at once.
	92	*/
	93	schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
	94	}
	95	}
	96
1da177e4 LT	97	void end_cpu_work(void)
	98	{
	99	int i;
	100
	101	work_enabled = 0;
	102
	103	for_each_online_cpu(i) {
608dfddd	104	struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
1da177e4 LT	105
	106	cancel_delayed_work(&b->work);
	107	}
	108
	109	flush_scheduled_work();
	110	}
	111
1da177e4 LT	112	/* Resets the cpu buffer to a sane state. */
	113	void cpu_buffer_reset(struct oprofile_cpu_buffer * cpu_buf)
	114	{
	115	/* reset these to invalid values; the next sample
	116	* collected will populate the buffer with proper
	117	* values to initialize the buffer
	118	*/
	119	cpu_buf->last_is_kernel = -1;
	120	cpu_buf->last_task = NULL;
	121	}
	122
1da177e4 LT	123	/* compute number of available slots in cpu_buffer queue */
	124	static unsigned long nr_available_slots(struct oprofile_cpu_buffer const * b)
	125	{
	126	unsigned long head = b->head_pos;
	127	unsigned long tail = b->tail_pos;
	128
	129	if (tail > head)
	130	return (tail - head) - 1;
	131
	132	return tail + (b->buffer_size - head) - 1;
	133	}
	134
1da177e4 LT	135	static void increment_head(struct oprofile_cpu_buffer * b)
	136	{
	137	unsigned long new_head = b->head_pos + 1;
	138
	139	/* Ensure anything written to the slot before we
	140	* increment is visible */
	141	wmb();
	142
	143	if (new_head < b->buffer_size)
	144	b->head_pos = new_head;
	145	else
	146	b->head_pos = 0;
	147	}
	148
77933d72	149	static inline void
1da177e4 LT	150	add_sample(struct oprofile_cpu_buffer * cpu_buf,
	151	unsigned long pc, unsigned long event)
	152	{
	153	struct op_sample * entry = &cpu_buf->buffer[cpu_buf->head_pos];
	154	entry->eip = pc;
	155	entry->event = event;
	156	increment_head(cpu_buf);
	157	}
	158
77933d72	159	static inline void
1da177e4 LT	160	add_code(struct oprofile_cpu_buffer * buffer, unsigned long value)
	161	{
	162	add_sample(buffer, ESCAPE_CODE, value);
	163	}
	164
1da177e4 LT	165	/* This must be safe from any context. It's safe writing here
	166	* because of the head/tail separation of the writer and reader
	167	* of the CPU buffer.
	168	*
	169	* is_kernel is needed because on some architectures you cannot
	170	* tell if you are in kernel or user space simply by looking at
	171	* pc. We tag this in the buffer by generating kernel enter/exit
	172	* events whenever is_kernel changes
	173	*/
	174	static int log_sample(struct oprofile_cpu_buffer * cpu_buf, unsigned long pc,
	175	int is_kernel, unsigned long event)
	176	{
	177	struct task_struct * task;
	178
	179	cpu_buf->sample_received++;
	180
df9d177a PE	181	if (pc == ESCAPE_CODE) {
	182	cpu_buf->sample_invalid_eip++;
	183	return 0;
	184	}
	185
1da177e4 LT	186	if (nr_available_slots(cpu_buf) < 3) {
	187	cpu_buf->sample_lost_overflow++;
	188	return 0;
	189	}
	190
	191	is_kernel = !!is_kernel;
	192
	193	task = current;
	194
	195	/* notice a switch from user->kernel or vice versa */
	196	if (cpu_buf->last_is_kernel != is_kernel) {
	197	cpu_buf->last_is_kernel = is_kernel;
	198	add_code(cpu_buf, is_kernel);
	199	}
	200
	201	/* notice a task switch */
	202	if (cpu_buf->last_task != task) {
	203	cpu_buf->last_task = task;
	204	add_code(cpu_buf, (unsigned long)task);
	205	}
	206
	207	add_sample(cpu_buf, pc, event);
	208	return 1;
	209	}
	210
345c2573	211	static int oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
1da177e4 LT	212	{
	213	if (nr_available_slots(cpu_buf) < 4) {
	214	cpu_buf->sample_lost_overflow++;
	215	return 0;
	216	}
	217
	218	add_code(cpu_buf, CPU_TRACE_BEGIN);
	219	cpu_buf->tracing = 1;
	220	return 1;
	221	}
	222
1da177e4 LT	223	static void oprofile_end_trace(struct oprofile_cpu_buffer * cpu_buf)
	224	{
	225	cpu_buf->tracing = 0;
	226	}
	227
27357716 BR	228	void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
27357716 BR	229	unsigned long event, int is_kernel)
1da177e4	230	{
608dfddd	231	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
1da177e4 LT	232
	233	if (!backtrace_depth) {
	234	log_sample(cpu_buf, pc, is_kernel, event);
	235	return;
	236	}
	237
	238	if (!oprofile_begin_trace(cpu_buf))
	239	return;
	240
	241	/* if log_sample() fail we can't backtrace since we lost the source
	242	* of this event */
	243	if (log_sample(cpu_buf, pc, is_kernel, event))
	244	oprofile_ops.backtrace(regs, backtrace_depth);
	245	oprofile_end_trace(cpu_buf);
	246	}
	247
27357716 BR	248	void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
	249	{
	250	int is_kernel = !user_mode(regs);
	251	unsigned long pc = profile_pc(regs);
	252
	253	oprofile_add_ext_sample(pc, regs, event, is_kernel);
	254	}
	255
345c2573 BK	256	#define MAX_IBS_SAMPLE_SIZE 14
	257	static int log_ibs_sample(struct oprofile_cpu_buffer *cpu_buf,
	258	unsigned long pc, int is_kernel, unsigned int *ibs, int ibs_code)
	259	{
	260	struct task_struct *task;
	261
	262	cpu_buf->sample_received++;
	263
	264	if (nr_available_slots(cpu_buf) < MAX_IBS_SAMPLE_SIZE) {
	265	cpu_buf->sample_lost_overflow++;
	266	return 0;
	267	}
	268
	269	is_kernel = !!is_kernel;
	270
	271	/* notice a switch from user->kernel or vice versa */
	272	if (cpu_buf->last_is_kernel != is_kernel) {
	273	cpu_buf->last_is_kernel = is_kernel;
	274	add_code(cpu_buf, is_kernel);
	275	}
	276
	277	/* notice a task switch */
	278	if (!is_kernel) {
	279	task = current;
	280
	281	if (cpu_buf->last_task != task) {
	282	cpu_buf->last_task = task;
	283	add_code(cpu_buf, (unsigned long)task);
	284	}
	285	}
	286
	287	add_code(cpu_buf, ibs_code);
	288	add_sample(cpu_buf, ibs[0], ibs[1]);
	289	add_sample(cpu_buf, ibs[2], ibs[3]);
	290	add_sample(cpu_buf, ibs[4], ibs[5]);
	291
	292	if (ibs_code == IBS_OP_BEGIN) {
	293	add_sample(cpu_buf, ibs[6], ibs[7]);
	294	add_sample(cpu_buf, ibs[8], ibs[9]);
	295	add_sample(cpu_buf, ibs[10], ibs[11]);
	296	}
	297
	298	return 1;
	299	}
	300
	301	void oprofile_add_ibs_sample(struct pt_regs *const regs,
	302	unsigned int * const ibs_sample, u8 code)
	303	{
	304	int is_kernel = !user_mode(regs);
	305	unsigned long pc = profile_pc(regs);
	306
	307	struct oprofile_cpu_buffer *cpu_buf =
	308	&per_cpu(cpu_buffer, smp_processor_id());
	309
	310	if (!backtrace_depth) {
	311	log_ibs_sample(cpu_buf, pc, is_kernel, ibs_sample, code);
	312	return;
	313	}
	314
	315	/* if log_sample() fails we can't backtrace since we lost the source
	316	* of this event */
	317	if (log_ibs_sample(cpu_buf, pc, is_kernel, ibs_sample, code))
	318	oprofile_ops.backtrace(regs, backtrace_depth);
	319	}
320
1da177e4 LT	321	void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
1da177e4 LT	322	{
608dfddd	323	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
1da177e4 LT	324	log_sample(cpu_buf, pc, is_kernel, event);
	325	}
	326
1da177e4 LT	327	void oprofile_add_trace(unsigned long pc)
1da177e4 LT	328	{
608dfddd	329	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
1da177e4 LT	330
	331	if (!cpu_buf->tracing)
	332	return;
	333
	334	if (nr_available_slots(cpu_buf) < 1) {
	335	cpu_buf->tracing = 0;
	336	cpu_buf->sample_lost_overflow++;
	337	return;
	338	}
	339
	340	/* broken frame can give an eip with the same value as an escape code,
	341	* abort the trace if we get it */
	342	if (pc == ESCAPE_CODE) {
	343	cpu_buf->tracing = 0;
	344	cpu_buf->backtrace_aborted++;
	345	return;
	346	}
	347
	348	add_sample(cpu_buf, pc, 0);
	349	}
	350
1da177e4 LT	351	/*
	352	* This serves to avoid cpu buffer overflow, and makes sure
	353	* the task mortuary progresses
	354	*
	355	* By using schedule_delayed_work_on and then schedule_delayed_work
	356	* we guarantee this will stay on the correct cpu
	357	*/
c4028958	358	static void wq_sync_buffer(struct work_struct *work)
1da177e4	359	{
c4028958 DH	360	struct oprofile_cpu_buffer * b =
c4028958 DH	361	container_of(work, struct oprofile_cpu_buffer, work.work);
1da177e4 LT	362	if (b->cpu != smp_processor_id()) {
	363	printk("WQ on CPU%d, prefer CPU%d\n",
	364	smp_processor_id(), b->cpu);
	365	}
	366	sync_buffer(b->cpu);
	367
	368	/* don't re-add the work if we're shutting down */
	369	if (work_enabled)
	370	schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
	371	}