[patch 16/49] JFFS2: Fix lack of locking in thread_should_wake()

Greg KH
2008-11-12T00:32:01Z

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2.6.27-stable review patch. If anyone has any objections, please let us know.

------------------

From: David Woodhouse <David.Woodhouse@intel.com>

commit b27cf88e9592953ae292d05324887f2f44979433 upstream

The thread_should_wake() function trawls through the list of 'very
dirty' eraseblocks, determining whether the background GC thread should
wake. Doing this without holding the appropriate locks is a bad idea.

OLPC Trac #8615

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/jffs2/background.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- a/fs/jffs2/background.c
+++ b/fs/jffs2/background.c
@@ -85,15 +85,15 @@ static int jffs2_garbage_collect_thread(
for (;;) {
allow_signal(SIGHUP);
again:
+ spin_lock(&c->erase_completion_lock);
if (!jffs2_thread_should_wake(c)) {
set_current_state (TASK_INTERRUPTIBLE);
+ spin_unlock(&c->erase_completion_lock);
D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
- /* Yes, there's a race here; we checked jffs2_thread_should_wake()
- before setting current->state to TASK_INTERRUPTIBLE. But it doesn't
- matter - We don't care if we miss a wakeup, because the GC thread
- is only an optimisation anyway. */
schedule();
- }
+ } else
+ spin_unlock(&c->erase_completion_lock);
+

/* This thread is purely an optimisation. But if it runs when
other things could be running, it actually makes things a

--