/** * @file cpu_buffer.c * * @remark Copyright 2002 OProfile authors * @remark Read the file COPYING * * @author John Levon <levon@movementarian.org> * * 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" struct oprofile_cpu_buffer cpu_buffer[NR_CPUS] __cacheline_aligned; 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(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 = &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->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 = &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 = &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 voidadd_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 voidadd_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 (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 = &cpu_buffer[smp_processor_id()]; 	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);} void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event){	struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()];	log_sample(cpu_buf, pc, is_kernel, event);} void oprofile_add_trace(unsigned long pc){	struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()]; 	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);}