1 files changed, 307 insertions, 0 deletions
diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
new file mode 100644
index 000000000000..e9b1772a3a28
--- /dev/null
+++ b/drivers/oprofile/cpu_buffer.c
@@ -0,0 +1,307 @@
+/**
+ * @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(void *);
+
+#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(sizeof(struct op_sample) * buffer_size);
+		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_WORK(&b->work, wq_sync_buffer, b);
+	}
+	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;
+}
+
+
+
+
+inline static 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);
+}
+
+
+inline static 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 (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_sample(struct pt_regs * const regs, unsigned long event)
+{
+	struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()];
+	unsigned long pc = profile_pc(regs);
+	int is_kernel = !user_mode(regs);
+
+	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_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(void * data)
+{
+	struct oprofile_cpu_buffer * b = data;
+	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);
+}