From: Xiongwei Song <sxwjean@me.com>
To: peterz@infradead.org, mingo@redhat.com, will@kernel.org,
longman@redhat.com, boqun.feng@gmail.com
Cc: linux-kernel@vger.kernel.org, Xiongwei Song <sxwjean@gmail.com>
Subject: [PATCH v2 3/3] locking/lockdep: Print possible warning after counting deps
Date: Fri, 18 Jun 2021 22:55:34 +0800 [thread overview]
Message-ID: <20210618145534.438816-4-sxwjean@me.com> (raw)
In-Reply-To: <20210618145534.438816-1-sxwjean@me.com>
From: Xiongwei Song <sxwjean@gmail.com>
The graph walk might hit error when counting dependencies. Once the
return value is negative, print a warning to reminder users.
However, lockdep_unlock() would be called twice if we call print_bfs_bug()
directly in __lockdep_count_*_deps(), so as the suggestion from Boqun:
"
Here print_bfs_bug() will eventually call debug_locks_off_graph_unlock()
to release the graph lock, and the caller (lockdep_count_fowards_deps())
will also call graph_unlock() afterwards, and that means we unlock
*twice* if a BFS error happens... although in that case, lockdep should
stop working so messing up with the graph lock may not hurt anything,
but still, I don't think we want to do that.
So probably you can open-code __lockdep_count_forward_deps() into
lockdep_count_forwards_deps(), and call print_bfs_bug() or
graph_unlock() accordingly. The body of __lockdep_count_forward_deps()
is really small, so I think it's OK to open-code it into its caller.
"
we put the code in __lockdep_count_*_deps() into lockdep_count_*_deps().
Suggested-by: Waiman Long <longman@redhat.com>
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
---
kernel/locking/lockdep.c | 45 +++++++++++++++++++---------------------
1 file changed, 21 insertions(+), 24 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index cb94097014d8..c29453b1df50 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2024,55 +2024,52 @@ static bool noop_count(struct lock_list *entry, void *data)
return false;
}
-static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
-{
- unsigned long count = 0;
- struct lock_list *target_entry;
-
- __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
-
- return count;
-}
unsigned long lockdep_count_forward_deps(struct lock_class *class)
{
- unsigned long ret, flags;
+ unsigned long count = 0, flags;
struct lock_list this;
+ struct lock_list *target_entry;
+ enum bfs_result result;
__bfs_init_root(&this, class);
raw_local_irq_save(flags);
lockdep_lock();
- ret = __lockdep_count_forward_deps(&this);
- lockdep_unlock();
- raw_local_irq_restore(flags);
- return ret;
-}
+ result = __bfs_forwards(&this, (void *)&count, noop_count, NULL, &target_entry);
-static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
-{
- unsigned long count = 0;
- struct lock_list *target_entry;
+ if (bfs_error(result))
+ print_bfs_bug(result);
+ else
+ lockdep_unlock();
- __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
+ raw_local_irq_restore(flags);
return count;
}
unsigned long lockdep_count_backward_deps(struct lock_class *class)
{
- unsigned long ret, flags;
+ unsigned long count = 0, flags;
struct lock_list this;
+ struct lock_list *target_entry;
+ enum bfs_result result;
__bfs_init_root(&this, class);
raw_local_irq_save(flags);
lockdep_lock();
- ret = __lockdep_count_backward_deps(&this);
- lockdep_unlock();
+
+ result = __bfs_backwards(&this, (void *)&count, noop_count, NULL, &target_entry);
+
+ if (bfs_error(result))
+ print_bfs_bug(result);
+ else
+ lockdep_unlock();
+
raw_local_irq_restore(flags);
- return ret;
+ return count;
}
/*
--
2.30.2
next prev parent reply other threads:[~2021-06-18 14:56 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-18 14:55 [PATCH v2 0/3] some improvements for lockdep Xiongwei Song
2021-06-18 14:55 ` [PATCH v2 1/3] locking/lockdep: Unlikely bfs_error() inside Xiongwei Song
2021-06-18 14:55 ` [PATCH v2 2/3] locking/lockdep: Unlikely conditons about BFS_RMATCH Xiongwei Song
2021-06-18 14:55 ` Xiongwei Song [this message]
2021-06-24 8:03 ` [PATCH v2 3/3] locking/lockdep: Print possible warning after counting deps Xiongwei Song
2021-06-24 13:45 ` Boqun Feng
2021-07-12 8:19 ` [PATCH v2 0/3] some improvements for lockdep Xiongwei Song
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