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Subject[PATCH 2/2] lockdep: Fix the rollback and overwrite detection in crossrelease
Date
As Boqun pointed out, current->hist_id should be aligned with the latest
valid xhlock->hist_id so that hist_id_save[] storing current->hist_id
can be comparable with xhlock->hist_id. Fix it.

Additionally, the condition for overwrite-detection should be the
opposite. Fix it with modifying comment.

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Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
kernel/locking/lockdep.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1ae4258..f0e6649 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4853,7 +4853,7 @@ static void add_xhlock(struct held_lock *hlock)

/* Initialize hist_lock's members */
xhlock->hlock = *hlock;
- xhlock->hist_id = current->hist_id++;
+ xhlock->hist_id = ++current->hist_id;

xhlock->trace.nr_entries = 0;
xhlock->trace.max_entries = MAX_XHLOCK_TRACE_ENTRIES;
@@ -5030,11 +5030,11 @@ static void commit_xhlocks(struct cross_lock *xlock)

/*
* Filter out the cases that the ring buffer was
- * overwritten and the previous entry has a bigger
- * hist_id than the following one, which is impossible
+ * overwritten and the current entry has a bigger
+ * hist_id than the previous one, which is impossible
* otherwise.
*/
- if (unlikely(before(xhlock->hist_id, prev_hist_id)))
+ if (unlikely(before(prev_hist_id, xhlock->hist_id)))
break;

prev_hist_id = xhlock->hist_id;
--
1.9.1
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