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-rw-r--r--kernel/trace/ring_buffer.c182
1 files changed, 177 insertions, 5 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 94af1fe56bb4..668bbb5ef2bd 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -16,14 +16,49 @@
#include <linux/list.h>
#include <linux/fs.h>
+#include "trace.h"
+
+/* Global flag to disable all recording to ring buffers */
+static int ring_buffers_off __read_mostly;
+
+/**
+ * tracing_on - enable all tracing buffers
+ *
+ * This function enables all tracing buffers that may have been
+ * disabled with tracing_off.
+ */
+void tracing_on(void)
+{
+ ring_buffers_off = 0;
+}
+
+/**
+ * tracing_off - turn off all tracing buffers
+ *
+ * This function stops all tracing buffers from recording data.
+ * It does not disable any overhead the tracers themselves may
+ * be causing. This function simply causes all recording to
+ * the ring buffers to fail.
+ */
+void tracing_off(void)
+{
+ ring_buffers_off = 1;
+}
+
/* Up this if you want to test the TIME_EXTENTS and normalization */
#define DEBUG_SHIFT 0
/* FIXME!!! */
u64 ring_buffer_time_stamp(int cpu)
{
+ u64 time;
+
+ preempt_disable_notrace();
/* shift to debug/test normalization and TIME_EXTENTS */
- return sched_clock() << DEBUG_SHIFT;
+ time = sched_clock() << DEBUG_SHIFT;
+ preempt_enable_notrace();
+
+ return time;
}
void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
@@ -130,7 +165,7 @@ struct buffer_page {
static inline void free_buffer_page(struct buffer_page *bpage)
{
if (bpage->page)
- __free_page(bpage->page);
+ free_page((unsigned long)bpage->page);
kfree(bpage);
}
@@ -503,6 +538,12 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
LIST_HEAD(pages);
int i, cpu;
+ /*
+ * Always succeed at resizing a non-existent buffer:
+ */
+ if (!buffer)
+ return size;
+
size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
size *= BUF_PAGE_SIZE;
buffer_size = buffer->pages * BUF_PAGE_SIZE;
@@ -576,6 +617,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
list_del_init(&page->list);
free_buffer_page(page);
}
+ mutex_unlock(&buffer->mutex);
return -ENOMEM;
}
@@ -966,7 +1008,9 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
if (unlikely(*delta > (1ULL << 59) && !once++)) {
printk(KERN_WARNING "Delta way too big! %llu"
" ts=%llu write stamp = %llu\n",
- *delta, *ts, cpu_buffer->write_stamp);
+ (unsigned long long)*delta,
+ (unsigned long long)*ts,
+ (unsigned long long)cpu_buffer->write_stamp);
WARN_ON(1);
}
@@ -1020,8 +1064,23 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event;
u64 ts, delta;
int commit = 0;
+ int nr_loops = 0;
again:
+ /*
+ * We allow for interrupts to reenter here and do a trace.
+ * If one does, it will cause this original code to loop
+ * back here. Even with heavy interrupts happening, this
+ * should only happen a few times in a row. If this happens
+ * 1000 times in a row, there must be either an interrupt
+ * storm or we have something buggy.
+ * Bail!
+ */
+ if (unlikely(++nr_loops > 1000)) {
+ RB_WARN_ON(cpu_buffer, 1);
+ return NULL;
+ }
+
ts = ring_buffer_time_stamp(cpu_buffer->cpu);
/*
@@ -1043,7 +1102,7 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
/* Did the write stamp get updated already? */
if (unlikely(ts < cpu_buffer->write_stamp))
- goto again;
+ delta = 0;
if (test_time_stamp(delta)) {
@@ -1116,6 +1175,9 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer,
struct ring_buffer_event *event;
int cpu, resched;
+ if (ring_buffers_off)
+ return NULL;
+
if (atomic_read(&buffer->record_disabled))
return NULL;
@@ -1153,7 +1215,7 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer,
out:
if (resched)
- preempt_enable_notrace();
+ preempt_enable_no_resched_notrace();
else
preempt_enable_notrace();
return NULL;
@@ -1232,6 +1294,9 @@ int ring_buffer_write(struct ring_buffer *buffer,
int ret = -EBUSY;
int cpu, resched;
+ if (ring_buffers_off)
+ return -EBUSY;
+
if (atomic_read(&buffer->record_disabled))
return -EBUSY;
@@ -1530,10 +1595,23 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *reader = NULL;
unsigned long flags;
+ int nr_loops = 0;
spin_lock_irqsave(&cpu_buffer->lock, flags);
again:
+ /*
+ * This should normally only loop twice. But because the
+ * start of the reader inserts an empty page, it causes
+ * a case where we will loop three times. There should be no
+ * reason to loop four times (that I know of).
+ */
+ if (unlikely(++nr_loops > 3)) {
+ RB_WARN_ON(cpu_buffer, 1);
+ reader = NULL;
+ goto out;
+ }
+
reader = cpu_buffer->reader_page;
/* If there's more to read, return this page */
@@ -1663,6 +1741,7 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
struct buffer_page *reader;
+ int nr_loops = 0;
if (!cpu_isset(cpu, buffer->cpumask))
return NULL;
@@ -1670,6 +1749,19 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
cpu_buffer = buffer->buffers[cpu];
again:
+ /*
+ * We repeat when a timestamp is encountered. It is possible
+ * to get multiple timestamps from an interrupt entering just
+ * as one timestamp is about to be written. The max times
+ * that this can happen is the number of nested interrupts we
+ * can have. Nesting 10 deep of interrupts is clearly
+ * an anomaly.
+ */
+ if (unlikely(++nr_loops > 10)) {
+ RB_WARN_ON(cpu_buffer, 1);
+ return NULL;
+ }
+
reader = rb_get_reader_page(cpu_buffer);
if (!reader)
return NULL;
@@ -1720,6 +1812,7 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
struct ring_buffer *buffer;
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
+ int nr_loops = 0;
if (ring_buffer_iter_empty(iter))
return NULL;
@@ -1728,6 +1821,19 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
buffer = cpu_buffer->buffer;
again:
+ /*
+ * We repeat when a timestamp is encountered. It is possible
+ * to get multiple timestamps from an interrupt entering just
+ * as one timestamp is about to be written. The max times
+ * that this can happen is the number of nested interrupts we
+ * can have. Nesting 10 deep of interrupts is clearly
+ * an anomaly.
+ */
+ if (unlikely(++nr_loops > 10)) {
+ RB_WARN_ON(cpu_buffer, 1);
+ return NULL;
+ }
+
if (rb_per_cpu_empty(cpu_buffer))
return NULL;
@@ -2012,3 +2118,69 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
return 0;
}
+static ssize_t
+rb_simple_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ int *p = filp->private_data;
+ char buf[64];
+ int r;
+
+ /* !ring_buffers_off == tracing_on */
+ r = sprintf(buf, "%d\n", !*p);
+
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+rb_simple_write(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ int *p = filp->private_data;
+ char buf[64];
+ long val;
+ int ret;
+
+ if (cnt >= sizeof(buf))
+ return -EINVAL;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+
+ buf[cnt] = 0;
+
+ ret = strict_strtoul(buf, 10, &val);
+ if (ret < 0)
+ return ret;
+
+ /* !ring_buffers_off == tracing_on */
+ *p = !val;
+
+ (*ppos)++;
+
+ return cnt;
+}
+
+static struct file_operations rb_simple_fops = {
+ .open = tracing_open_generic,
+ .read = rb_simple_read,
+ .write = rb_simple_write,
+};
+
+
+static __init int rb_init_debugfs(void)
+{
+ struct dentry *d_tracer;
+ struct dentry *entry;
+
+ d_tracer = tracing_init_dentry();
+
+ entry = debugfs_create_file("tracing_on", 0644, d_tracer,
+ &ring_buffers_off, &rb_simple_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs 'tracing_on' entry\n");
+
+ return 0;
+}
+
+fs_initcall(rb_init_debugfs);