Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

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 4451aa3a55a0f56400d8ae11b12700af1bb53ecf..7693aaf324c655d325b1739014c032aba76856b4 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2437,7 +2437,7 @@ static void reset_iter_read(struct ftrace_iterator *iter)
 {
        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 3c7834c24e54e6630a286423cfd17ba3d6b61350..ce8514feedcdf29c181dda4972eb7a53cd0df04e 100644 (file)
--- 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);