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Message-ID: <f498d8cc-ba82-d3dc-7557-142a1b35976a@acm.org>
Date: Wed, 10 Jul 2019 10:46:00 -0700
From: Bart Van Assche <bvanassche@....org>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
linux-kernel@...r.kernel.org,
syzbot <syzbot+6f39a9deb697359fe520@...kaller.appspotmail.com>,
syzkaller-bugs@...glegroups.com
Subject: Re: BUG: MAX_STACK_TRACE_ENTRIES too low! (2)
On 7/10/19 10:21 AM, Eric Biggers wrote:
> With my simplified reproducer, on commit 669de8bda87b ("kernel/workqueue: Use
> dynamic lockdep keys for workqueues") I see:
>
> WARNING: CPU: 3 PID: 189 at kernel/locking/lockdep.c:747 register_lock_class+0x4f6/0x580
>
> and then somewhat later:
>
> BUG: MAX_LOCKDEP_KEYS too low!
>
> If on top of that I cherry pick commit 28d49e282665 ("locking/lockdep: Shrink
> struct lock_class_key"), I see instead:
>
> BUG: MAX_STACK_TRACE_ENTRIES too low!
>
> I also see that on mainline.
>
> Alternatively, if I check out 669de8bda87b and revert it, I don't see anything.
Hi Eric,
Is the rdma_ucm code the only code that triggers the "BUG:
MAX_STACK_TRACE_ENTRIES too low!" complaint or is this complaint also
triggered by other kernel code? I'm asking this because I think that
fixing this would require to implement garbage collection for the
stack_trace[] array in the lockdep code. That would make the lockdep
code slower. I don't think that making the lockdep code slower would be
welcome.
Bart.
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