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Subject[tip:locking/core] locking/lockdep: Change the meaning of check_prev_add()'s return value
Commit-ID:  70911fdc9576f4eeb3986689a1c9a778a4a4aacb
Gitweb: http://git.kernel.org/tip/70911fdc9576f4eeb3986689a1c9a778a4a4aacb
Author: Byungchul Park <byungchul.park@lge.com>
AuthorDate: Mon, 7 Aug 2017 16:12:50 +0900
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 10 Aug 2017 12:29:06 +0200

locking/lockdep: Change the meaning of check_prev_add()'s return value

Firstly, return 1 instead of 2 when 'prev -> next' dependency already
exists. Since the value 2 is not referenced anywhere, just return 1
indicating success in this case.

Secondly, return 2 instead of 1 when successfully added a lock_list
entry with saving stack_trace. With that, a caller can decide whether
to avoid redundant save_trace() on the caller site.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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: boqun.feng@gmail.com
Cc: kernel-team@lge.com
Cc: kirill@shutemov.name
Cc: npiggin@gmail.com
Cc: walken@google.com
Cc: willy@infradead.org
Link: http://lkml.kernel.org/r/1502089981-21272-4-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/locking/lockdep.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index bdf6b31..7cf02fa 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1881,7 +1881,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
if (entry->class == hlock_class(next)) {
if (distance == 1)
entry->distance = 1;
- return 2;
+ return 1;
}
}

@@ -1935,9 +1935,10 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
print_lock_name(hlock_class(next));
printk(KERN_CONT "\n");
dump_stack();
- return graph_lock();
+ if (!graph_lock())
+ return 0;
}
- return 1;
+ return 2;
}

/*
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