Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar:
"These are late-v3.7 pending fixes for tracing."
Fix up trivial conflict in kernel/trace/ring_buffer.c: the NULL pointer
fix clashed with the change of type of the 'ret' variable.
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
ring-buffer: Fix race between integrity check and readers
ring-buffer: Fix NULL pointer if rb_set_head_page() fails
ftrace: Clear bits properly in reset_iter_read()
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 4451aa3..7693aaf 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2437,7 +2437,7 @@
{
iter->pos = 0;
iter->func_pos = 0;
- iter->flags &= ~(FTRACE_ITER_PRINTALL & FTRACE_ITER_HASH);
+ iter->flags &= ~(FTRACE_ITER_PRINTALL | FTRACE_ITER_HASH);
}
static void *t_start(struct seq_file *m, loff_t *pos)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 3c7834c..ce8514fe 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1397,6 +1397,8 @@
struct list_head *head_page_with_bit;
head_page = &rb_set_head_page(cpu_buffer)->list;
+ if (!head_page)
+ break;
prev_page = head_page->prev;
first_page = pages->next;
@@ -2937,7 +2939,7 @@
unsigned long flags;
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_page *bpage;
- u64 ret;
+ u64 ret = 0;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
@@ -2952,7 +2954,8 @@
bpage = cpu_buffer->reader_page;
else
bpage = rb_set_head_page(cpu_buffer);
- ret = bpage->page->time_stamp;
+ if (bpage)
+ ret = bpage->page->time_stamp;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
return ret;
@@ -3288,6 +3291,8 @@
* Splice the empty reader page into the list around the head.
*/
reader = rb_set_head_page(cpu_buffer);
+ if (!reader)
+ goto out;
cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
cpu_buffer->reader_page->list.prev = reader->list.prev;
@@ -3806,12 +3811,17 @@
ring_buffer_read_finish(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+ unsigned long flags;
/*
* Ring buffer is disabled from recording, here's a good place
- * to check the integrity of the ring buffer.
+ * to check the integrity of the ring buffer.
+ * Must prevent readers from trying to read, as the check
+ * clears the HEAD page and readers require it.
*/
+ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_check_pages(cpu_buffer);
+ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
atomic_dec(&cpu_buffer->record_disabled);
atomic_dec(&cpu_buffer->buffer->resize_disabled);
