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From: Julia Lawall on 29 Mar 2010 11:40
From: Julia Lawall <julia(a)diku.dk>

In some error handling cases the lock is not unlocked. The return is
converted to a goto, to share the unlock at the end of the function.

A simplified version of the semantic patch that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@r exists@
expression E1;
identifier f;
@@

f (...) { <+...
* spin_lock_irq (E1,...);
.... when != E1
* return ...;
....+> }
// </smpl>

Signed-off-by: Julia Lawall <julia(a)diku.dk>

---
kernel/trace/ring_buffer.c | 8 +++++---
1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 05a9f83..cd2e1d8 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1201,18 +1201,19 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)

for (i = 0; i < nr_pages; i++) {
if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
- return;
+ goto out;
p = cpu_buffer->pages->next;
bpage = list_entry(p, struct buffer_page, list);
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
- return;
+ goto out;

rb_reset_cpu(cpu_buffer);
rb_check_pages(cpu_buffer);

+out:
spin_unlock_irq(&cpu_buffer->reader_lock);
}

@@ -1229,7 +1230,7 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,

for (i = 0; i < nr_pages; i++) {
if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
- return;
+ goto out;
p = pages->next;
bpage = list_entry(p, struct buffer_page, list);
list_del_init(&bpage->list);
@@ -1238,6 +1239,7 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
rb_reset_cpu(cpu_buffer);
rb_check_pages(cpu_buffer);

+out:
spin_unlock_irq(&cpu_buffer->reader_lock);
}

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Prev: fbdev: section cleanup in efifb
Next: [PATCH 1/12] arch/powerpc/kernel: Add missing unlock