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locking/lockdep: Fix the rollback and overwrite detection logic in crossrelease 

As Boqun Feng 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 the code and the comments as well.

           <- direction to visit
hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh (h: history)
                 ^^        ^
                 ||        start from here
                 |previous entry
                 current entry

Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: kernel-team@lge.com
Cc: kirill@shutemov.name
Cc: linux-mm@kvack.org
Cc: npiggin@gmail.com
Cc: walken@google.com
Cc: willy@infradead.org
Link: http://lkml.kernel.org/r/1502694052-16085-3-git-send-email-byungchul.park@lge.com
[ Improve the comments some more. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Byungchul Park 2017-08-14 16:00:52 +09:00 committed by Ingo Molnar
parent a10b5c5647
commit 907dc16d7e
1 changed files with 6 additions and 6 deletions
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12
kernel/locking/lockdep.c
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@ -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;
@ -5029,12 +5029,12 @@ static void commit_xhlocks(struct cross_lock *xlock)
break;
/*
* 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
* otherwise.
* Filter out the cases where the ring buffer was
* 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;