From: Boqun Feng <boqun.feng@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Sedat Dilek <sedat.dilek@gmail.com>,
"Theodore Ts'o" <tytso@mit.edu>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260
Date: Wed, 30 Mar 2016 17:59:54 +0800 [thread overview]
Message-ID: <20160330095954.GB14352@fixme-laptop.cn.ibm.com> (raw)
In-Reply-To: <20160330093659.GS3408@twins.programming.kicks-ass.net>
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Hi Peter,
On Wed, Mar 30, 2016 at 11:36:59AM +0200, Peter Zijlstra wrote:
> On Tue, Mar 29, 2016 at 10:47:02AM +0200, Ingo Molnar wrote:
>
> > > You are right; this is lockdep running into a hash collision; which is a new
> > > DEBUG_LOCKDEP test. See 9e4e7554e755 ("locking/lockdep: Detect chain_key
> > > collisions").
> >
> > I've Cc:-ed Alfredo Alvarez Fernandez who added that test.
>
> OK, so while the code in check_no_collision() seems sensible, it relies
> on borken bits.
>
> The whole chain_hlocks and /proc/lockdep_chains stuff appears to have
> been buggered from the start.
>
> The below patch should fix this.
>
> Furthermore, our hash function has definite room for improvement.
>
> ---
> include/linux/lockdep.h | 8 +++++---
> kernel/locking/lockdep.c | 30 ++++++++++++++++++++++++------
> kernel/locking/lockdep_proc.c | 2 ++
> 3 files changed, 31 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index d026b190c530..2568c120513b 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -196,9 +196,11 @@ struct lock_list {
> * We record lock dependency chains, so that we can cache them:
> */
> struct lock_chain {
> - u8 irq_context;
> - u8 depth;
> - u16 base;
> + /* see BUILD_BUG_ON()s in lookup_chain_cache() */
> + unsigned int irq_context : 2,
> + depth : 6,
> + base : 24;
> + /* 4 byte hole */
> struct hlist_node entry;
> u64 chain_key;
> };
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 53ab2f85d77e..91a4b7780afb 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
[...]
> @@ -2860,11 +2882,6 @@ static int separate_irq_context(struct task_struct *curr,
> {
> unsigned int depth = curr->lockdep_depth;
>
> - /*
> - * Keep track of points where we cross into an interrupt context:
> - */
> - hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
> - curr->softirq_context;
> if (depth) {
> struct held_lock *prev_hlock;
>
> @@ -3164,6 +3181,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
> hlock->acquire_ip = ip;
> hlock->instance = lock;
> hlock->nest_lock = nest_lock;
> + hlock->irq_context = 2*(!!curr->hardirq_context) + !!curr->softirq_context;
> hlock->trylock = trylock;
> hlock->read = read;
> hlock->check = check;
This is just for cleaning up, right? However ->hardirq_context and
->softirq_context only defined when CONFIG_TRACE_IRQFLAGS=y.
So we should use macro like current_hardirq_context() here? Or
considering the two helpers introduced in my RFC:
http://lkml.kernel.org/g/1455602265-16490-2-git-send-email-boqun.feng@gmail.com
if you don't think that overkills ;-)
Regards,
Boqun
[...]
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next prev parent reply other threads:[~2016-03-30 10:00 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-27 8:15 [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260 Sedat Dilek
2016-03-27 8:57 ` Sedat Dilek
2016-03-27 12:03 ` Linus Torvalds
2016-03-27 13:32 ` Boqun Feng
2016-03-27 18:23 ` Theodore Ts'o
2016-03-27 19:40 ` Sedat Dilek
[not found] ` <CA+55aFwoKRpgq8OCTxUaP+8gOg-mnN3nbruYgiK32a=C5U4TkQ@mail.gmail.com>
2016-03-27 20:24 ` Sedat Dilek
2016-03-27 20:48 ` Peter Zijlstra
2016-03-27 20:59 ` Sedat Dilek
2016-03-27 21:48 ` Sedat Dilek
2016-03-28 1:05 ` Boqun Feng
2016-03-28 6:33 ` Peter Zijlstra
2016-03-29 8:47 ` Ingo Molnar
2016-03-30 9:20 ` Sedat Dilek
2016-03-30 9:36 ` Sedat Dilek
2016-03-30 9:36 ` Peter Zijlstra
2016-03-30 9:49 ` Sedat Dilek
2016-03-30 10:33 ` Sedat Dilek
2016-03-30 12:43 ` Peter Zijlstra
2016-03-30 12:46 ` Sedat Dilek
2016-03-30 13:15 ` Peter Zijlstra
2016-03-30 9:50 ` Peter Zijlstra
2016-03-30 9:59 ` Boqun Feng [this message]
2016-03-30 10:36 ` Peter Zijlstra
2016-03-30 11:07 ` Sedat Dilek
2016-03-31 15:42 ` Peter Zijlstra
2016-03-31 15:52 ` Boqun Feng
2016-04-02 6:26 ` Sedat Dilek
2016-03-30 14:06 ` Peter Zijlstra
2016-03-30 15:21 ` Sedat Dilek
2016-03-30 17:03 ` [PATCH] lockdep: print chain_key collision information Alfredo Alvarez Fernandez
2016-03-30 17:19 ` Peter Zijlstra
2016-04-01 6:36 ` [tip:core/urgent] locking/lockdep: Print " tip-bot for Alfredo Alvarez Fernandez
2016-05-10 9:09 ` Peter Zijlstra
2016-04-04 15:31 ` [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260 Sedat Dilek
2016-04-04 16:02 ` Peter Zijlstra
2016-05-09 11:37 ` Sedat Dilek
2016-06-03 15:15 ` Sedat Dilek
2016-04-23 12:54 ` [tip:locking/urgent] lockdep: Fix lock_chain::base size tip-bot for Peter Zijlstra
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