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authorLinus Torvalds <torvalds@linux-foundation.org>2012-12-12 06:18:58 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-12 06:18:58 +0400
commitda830e589a45f0c42eef6f3cbd07275f8893f181 (patch)
treeb241c86b8a0f9acdef4b90f69ddd200548e91f2c /kernel/trace/ring_buffer.c
parent090f8ccba37034cec5a5972a70abeaae7eb0222b (diff)
parent08cd2a6960ae2e1aa7f44b44ebafa84f503a2dd1 (diff)
downloadlinux-da830e589a45f0c42eef6f3cbd07275f8893f181.tar.xz
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()
Diffstat (limited to 'kernel/trace/ring_buffer.c')
-rw-r--r--kernel/trace/ring_buffer.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 3c7834c24e54..ce8514feedcd 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1397,6 +1397,8 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
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 @@ u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
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 @@ u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
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 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
* 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 @@ void
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);