[deliverable/linux.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 OP_BUFFER_FLAGS	0

/*
 * Read and write access is using spin locking. Thus, writing to the
 * buffer by NMI handler (x86) could occur also during critical
 * sections when reading the buffer. To avoid this, there are 2
 * buffers for independent read and write access. Read access is in
 * process context only, write access only in the NMI handler. If the
 * read buffer runs empty, both buffers are swapped atomically. There
 * is potentially a small window during swapping where the buffers are
 * disabled and samples could be lost.
 *
 * Using 2 buffers is a little bit overhead, but the solution is clear
 * and does not require changes in the ring buffer implementation. It
 * can be changed to a single buffer solution when the ring buffer
 * access is implemented as non-locking atomic code.
 */
struct ring_buffer *op_ring_buffer_read;
struct ring_buffer *op_ring_buffer_write;
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)
{
	if (op_ring_buffer_read)
		ring_buffer_free(op_ring_buffer_read);
	op_ring_buffer_read = NULL;
	if (op_ring_buffer_write)
		ring_buffer_free(op_ring_buffer_write);
	op_ring_buffer_write = NULL;
}

unsigned long oprofile_get_cpu_buffer_size(void)
{
	return fs_cpu_buffer_size;
}

void oprofile_cpu_buffer_inc_smpl_lost(void)
{
	struct oprofile_cpu_buffer *cpu_buf
		= &__get_cpu_var(cpu_buffer);

	cpu_buf->sample_lost_overflow++;
}

int alloc_cpu_buffers(void)
{
	int i;

	unsigned long buffer_size = fs_cpu_buffer_size;

	op_ring_buffer_read = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
	if (!op_ring_buffer_read)
		goto fail;
	op_ring_buffer_write = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
	if (!op_ring_buffer_write)
		goto fail;

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

		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();
}

static inline void
add_sample(struct oprofile_cpu_buffer *cpu_buf,
	   unsigned long pc, unsigned long event)
{
	struct op_entry entry;

	if (cpu_buffer_write_entry(&entry))
		goto Error;

	entry.sample->eip = pc;
	entry.sample->event = event;

	if (cpu_buffer_write_commit(&entry))
		goto Error;

	return;

Error:
	cpu_buf->sample_lost_overflow++;
	return;
}

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;
	}

	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)
{
	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);
}

#ifdef CONFIG_OPROFILE_IBS

#define MAX_IBS_SAMPLE_SIZE 14

void oprofile_add_ibs_sample(struct pt_regs * const regs,
			     unsigned int * const ibs_sample, int ibs_code)
{
	int is_kernel = !user_mode(regs);
	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
	struct task_struct *task;

	cpu_buf->sample_received++;

	/* 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_sample[0], ibs_sample[1]);
	add_sample(cpu_buf, ibs_sample[2], ibs_sample[3]);
	add_sample(cpu_buf, ibs_sample[4], ibs_sample[5]);

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

	if (backtrace_depth)
		oprofile_ops.backtrace(regs, backtrace_depth);
}

#endif

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;

	/*
	 * 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(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n",
		       smp_processor_id(), b->cpu);

		if (!cpu_online(b->cpu)) {
			cancel_delayed_work(&b->work);
			return;
		}
	}
	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>
6a18037d	25
1da177e4 LT	26	#include "event_buffer.h"
	27	#include "cpu_buffer.h"
	28	#include "buffer_sync.h"
	29	#include "oprof.h"
	30
6dad828b RR	31	#define OP_BUFFER_FLAGS 0
	32
	33	/*
	34	* Read and write access is using spin locking. Thus, writing to the
	35	* buffer by NMI handler (x86) could occur also during critical
	36	* sections when reading the buffer. To avoid this, there are 2
	37	* buffers for independent read and write access. Read access is in
	38	* process context only, write access only in the NMI handler. If the
	39	* read buffer runs empty, both buffers are swapped atomically. There
	40	* is potentially a small window during swapping where the buffers are
	41	* disabled and samples could be lost.
	42	*
	43	* Using 2 buffers is a little bit overhead, but the solution is clear
	44	* and does not require changes in the ring buffer implementation. It
	45	* can be changed to a single buffer solution when the ring buffer
	46	* access is implemented as non-locking atomic code.
	47	*/
	48	struct ring_buffer *op_ring_buffer_read;
	49	struct ring_buffer *op_ring_buffer_write;
8b8b4988	50	DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
1da177e4	51
c4028958	52	static void wq_sync_buffer(struct work_struct *work);
1da177e4 LT	53
	54	#define DEFAULT_TIMER_EXPIRE (HZ / 10)
	55	static int work_enabled;
	56
	57	void free_cpu_buffers(void)
	58	{
6dad828b RR	59	if (op_ring_buffer_read)
	60	ring_buffer_free(op_ring_buffer_read);
	61	op_ring_buffer_read = NULL;
	62	if (op_ring_buffer_write)
	63	ring_buffer_free(op_ring_buffer_write);
	64	op_ring_buffer_write = NULL;
1da177e4	65	}
77933d72	66
a5598ca0 CL	67	unsigned long oprofile_get_cpu_buffer_size(void)
	68	{
	69	return fs_cpu_buffer_size;
	70	}
	71
	72	void oprofile_cpu_buffer_inc_smpl_lost(void)
	73	{
	74	struct oprofile_cpu_buffer *cpu_buf
	75	= &__get_cpu_var(cpu_buffer);
	76
	77	cpu_buf->sample_lost_overflow++;
	78	}
	79
1da177e4 LT	80	int alloc_cpu_buffers(void)
	81	{
	82	int i;
6a18037d	83
1da177e4	84	unsigned long buffer_size = fs_cpu_buffer_size;
6a18037d	85
6dad828b RR	86	op_ring_buffer_read = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
	87	if (!op_ring_buffer_read)
	88	goto fail;
	89	op_ring_buffer_write = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
	90	if (!op_ring_buffer_write)
	91	goto fail;
	92
4bd9b9dc	93	for_each_possible_cpu(i) {
608dfddd	94	struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
6a18037d	95
1da177e4 LT	96	b->last_task = NULL;
	97	b->last_is_kernel = -1;
	98	b->tracing = 0;
	99	b->buffer_size = buffer_size;
	100	b->tail_pos = 0;
	101	b->head_pos = 0;
	102	b->sample_received = 0;
	103	b->sample_lost_overflow = 0;
df9d177a PE	104	b->backtrace_aborted = 0;
df9d177a PE	105	b->sample_invalid_eip = 0;
1da177e4	106	b->cpu = i;
c4028958	107	INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
1da177e4 LT	108	}
	109	return 0;
	110
	111	fail:
	112	free_cpu_buffers();
	113	return -ENOMEM;
	114	}
1da177e4 LT	115
	116	void start_cpu_work(void)
	117	{
	118	int i;
	119
	120	work_enabled = 1;
	121
	122	for_each_online_cpu(i) {
608dfddd	123	struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
1da177e4 LT	124
	125	/*
	126	* Spread the work by 1 jiffy per cpu so they dont all
	127	* fire at once.
	128	*/
	129	schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
	130	}
	131	}
	132
1da177e4 LT	133	void end_cpu_work(void)
	134	{
	135	int i;
	136
	137	work_enabled = 0;
	138
	139	for_each_online_cpu(i) {
608dfddd	140	struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
1da177e4 LT	141
	142	cancel_delayed_work(&b->work);
	143	}
	144
	145	flush_scheduled_work();
	146	}
	147
77933d72	148	static inline void
25ad2913	149	add_sample(struct oprofile_cpu_buffer *cpu_buf,
6a18037d	150	unsigned long pc, unsigned long event)
1da177e4	151	{
6dad828b RR	152	struct op_entry entry;
	153
	154	if (cpu_buffer_write_entry(&entry))
	155	goto Error;
	156
	157	entry.sample->eip = pc;
	158	entry.sample->event = event;
	159
	160	if (cpu_buffer_write_commit(&entry))
	161	goto Error;
	162
	163	return;
	164
	165	Error:
	166	cpu_buf->sample_lost_overflow++;
	167	return;
1da177e4 LT	168	}
1da177e4 LT	169
77933d72	170	static inline void
25ad2913	171	add_code(struct oprofile_cpu_buffer *buffer, unsigned long value)
1da177e4 LT	172	{
	173	add_sample(buffer, ESCAPE_CODE, value);
	174	}
	175
1da177e4 LT	176	/* This must be safe from any context. It's safe writing here
	177	* because of the head/tail separation of the writer and reader
	178	* of the CPU buffer.
	179	*
	180	* is_kernel is needed because on some architectures you cannot
	181	* tell if you are in kernel or user space simply by looking at
	182	* pc. We tag this in the buffer by generating kernel enter/exit
	183	* events whenever is_kernel changes
	184	*/
25ad2913	185	static int log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
1da177e4 LT	186	int is_kernel, unsigned long event)
1da177e4 LT	187	{
25ad2913	188	struct task_struct *task;
1da177e4 LT	189
	190	cpu_buf->sample_received++;
	191
df9d177a PE	192	if (pc == ESCAPE_CODE) {
	193	cpu_buf->sample_invalid_eip++;
	194	return 0;
	195	}
	196
1da177e4 LT	197	is_kernel = !!is_kernel;
	198
	199	task = current;
	200
	201	/* notice a switch from user->kernel or vice versa */
	202	if (cpu_buf->last_is_kernel != is_kernel) {
	203	cpu_buf->last_is_kernel = is_kernel;
	204	add_code(cpu_buf, is_kernel);
	205	}
	206
	207	/* notice a task switch */
	208	if (cpu_buf->last_task != task) {
	209	cpu_buf->last_task = task;
	210	add_code(cpu_buf, (unsigned long)task);
	211	}
6a18037d	212
1da177e4 LT	213	add_sample(cpu_buf, pc, event);
	214	return 1;
	215	}
	216
345c2573	217	static int oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
1da177e4	218	{
1da177e4 LT	219	add_code(cpu_buf, CPU_TRACE_BEGIN);
	220	cpu_buf->tracing = 1;
	221	return 1;
	222	}
	223
25ad2913	224	static void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf)
1da177e4 LT	225	{
	226	cpu_buf->tracing = 0;
	227	}
	228
27357716 BR	229	void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
27357716 BR	230	unsigned long event, int is_kernel)
1da177e4	231	{
608dfddd	232	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
1da177e4 LT	233
	234	if (!backtrace_depth) {
	235	log_sample(cpu_buf, pc, is_kernel, event);
	236	return;
	237	}
	238
	239	if (!oprofile_begin_trace(cpu_buf))
	240	return;
	241
fd13f6c8 RR	242	/*
	243	* if log_sample() fail we can't backtrace since we lost the
	244	* source of this event
	245	*/
1da177e4 LT	246	if (log_sample(cpu_buf, pc, is_kernel, event))
	247	oprofile_ops.backtrace(regs, backtrace_depth);
	248	oprofile_end_trace(cpu_buf);
	249	}
	250
27357716 BR	251	void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
	252	{
	253	int is_kernel = !user_mode(regs);
	254	unsigned long pc = profile_pc(regs);
	255
	256	oprofile_add_ext_sample(pc, regs, event, is_kernel);
	257	}
	258
852402cc RR	259	#ifdef CONFIG_OPROFILE_IBS
852402cc RR	260
e2fee276 RR	261	#define MAX_IBS_SAMPLE_SIZE 14
e2fee276 RR	262
cdc1834d RR	263	void oprofile_add_ibs_sample(struct pt_regs * const regs,
cdc1834d RR	264	unsigned int * const ibs_sample, int ibs_code)
345c2573	265	{
e2fee276 RR	266	int is_kernel = !user_mode(regs);
e2fee276 RR	267	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
345c2573 BK	268	struct task_struct *task;
	269
	270	cpu_buf->sample_received++;
	271
345c2573 BK	272	/* notice a switch from user->kernel or vice versa */
	273	if (cpu_buf->last_is_kernel != is_kernel) {
	274	cpu_buf->last_is_kernel = is_kernel;
	275	add_code(cpu_buf, is_kernel);
	276	}
	277
	278	/* notice a task switch */
	279	if (!is_kernel) {
	280	task = current;
345c2573 BK	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);
e2fee276 RR	288	add_sample(cpu_buf, ibs_sample[0], ibs_sample[1]);
	289	add_sample(cpu_buf, ibs_sample[2], ibs_sample[3]);
	290	add_sample(cpu_buf, ibs_sample[4], ibs_sample[5]);
345c2573 BK	291
345c2573 BK	292	if (ibs_code == IBS_OP_BEGIN) {
e2fee276 RR	293	add_sample(cpu_buf, ibs_sample[6], ibs_sample[7]);
	294	add_sample(cpu_buf, ibs_sample[8], ibs_sample[9]);
	295	add_sample(cpu_buf, ibs_sample[10], ibs_sample[11]);
345c2573 BK	296	}
345c2573 BK	297
e2fee276	298	if (backtrace_depth)
345c2573 BK	299	oprofile_ops.backtrace(regs, backtrace_depth);
	300	}
	301
852402cc RR	302	#endif
852402cc RR	303
1da177e4 LT	304	void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
1da177e4 LT	305	{
608dfddd	306	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
1da177e4 LT	307	log_sample(cpu_buf, pc, is_kernel, event);
	308	}
	309
1da177e4 LT	310	void oprofile_add_trace(unsigned long pc)
1da177e4 LT	311	{
608dfddd	312	struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
1da177e4 LT	313
	314	if (!cpu_buf->tracing)
	315	return;
	316
fd13f6c8 RR	317	/*
	318	* broken frame can give an eip with the same value as an
	319	* escape code, abort the trace if we get it
	320	*/
1da177e4 LT	321	if (pc == ESCAPE_CODE) {
	322	cpu_buf->tracing = 0;
	323	cpu_buf->backtrace_aborted++;
	324	return;
	325	}
	326
	327	add_sample(cpu_buf, pc, 0);
	328	}
	329
1da177e4 LT	330	/*
	331	* This serves to avoid cpu buffer overflow, and makes sure
	332	* the task mortuary progresses
	333	*
	334	* By using schedule_delayed_work_on and then schedule_delayed_work
	335	* we guarantee this will stay on the correct cpu
	336	*/
c4028958	337	static void wq_sync_buffer(struct work_struct *work)
1da177e4	338	{
25ad2913	339	struct oprofile_cpu_buffer *b =
c4028958	340	container_of(work, struct oprofile_cpu_buffer, work.work);
1da177e4	341	if (b->cpu != smp_processor_id()) {
bd17b625	342	printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n",
1da177e4	343	smp_processor_id(), b->cpu);
4bd9b9dc CA	344
	345	if (!cpu_online(b->cpu)) {
	346	cancel_delayed_work(&b->work);
	347	return;
	348	}
1da177e4 LT	349	}
	350	sync_buffer(b->cpu);
	351
	352	/* don't re-add the work if we're shutting down */
	353	if (work_enabled)
	354	schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
	355	}