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SubjectRe: linux-next oops in __lock_acquire for process_one_work
On Wed, 9 May 2012, Peter Zijlstra wrote:
> On Tue, 2012-05-08 at 11:11 -0700, Hugh Dickins wrote:
> > Please send me the version of patch you'd like to put in
> > (lest I make it up myself and you don't like the result).
>
> something like so?

More like the one below: I'm not alone in preferring a comma between args!

And you're not a believer in checkpatch.pl, I see: I've removed trailing
spaces; but left the 85-col line, that's not a fight I'll have with you.

I'll set it going when I get home later - thanks.

Hugh

---
include/linux/lockdep.h | 17 +++++++++++++++++
kernel/timer.c | 4 +++-
kernel/workqueue.c | 4 +++-
3 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index d36619e..968c3e2 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -157,6 +157,23 @@ struct lockdep_map {
#endif
};

+static inline void lockdep_copy_map(struct lockdep_map *to, struct lockdep_map *from)
+{
+ int i;
+
+ *to = *from;
+ /*
+ * Since the class cache can be modified concurrently we could observe
+ * half pointers (64bit arch using 32bit copy insns). Therefore clear
+ * the caches and take the performance hit.
+ *
+ * XXX it doesn't work well with lockdep_set_class_and_subclass(), since
+ * that relies on cache abuse.
+ */
+ for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
+ to->class_cache[i] = NULL;
+}
+
/*
* Every lock has a list of other locks that were taken after it.
* We only grow the list, never remove from it:
diff --git a/kernel/timer.c b/kernel/timer.c
index a297ffc..6aa7ad8 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1102,7 +1102,9 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
* warnings as well as problems when looking into
* timer->lockdep_map, make a copy and use that here.
*/
- struct lockdep_map lockdep_map = timer->lockdep_map;
+ struct lockdep_map lockdep_map;
+
+ lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
#endif
/*
* Couple the lock chain with the lock chain at
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 5abf42f..7d77d1f 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1810,7 +1810,9 @@ __acquires(&gcwq->lock)
* lock freed" warnings as well as problems when looking into
* work->lockdep_map, make a copy and use that here.
*/
- struct lockdep_map lockdep_map = work->lockdep_map;
+ struct lockdep_map lockdep_map;
+
+ lockdep_copy_map(&lockdep_map, &work->lockdep_map);
#endif
/*
* A single work shouldn't be executed concurrently by

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