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);
+}