linux-kernel - Re: BUG: MAX_STACK_TRACE

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Date:   Fri, 12 Jul 2019 10:55:36 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Bart Van Assche <bvanassche@....org>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        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 Thu, Jul 11, 2019 at 11:53:12AM -0700, Bart Van Assche wrote:
> On 7/10/19 3:09 PM, Peter Zijlstra wrote:
> > One thing I mentioned when Thomas did the unwinder API changes was
> > trying to move lockdep over to something like stackdepot.
> > 
> > We can't directly use stackdepot as is, because it uses locks and memory
> > allocation, but we could maybe add a lower level API to it and use that
> > under the graph_lock() on static storage or something.
> > 
> > Otherwise we'll have to (re)implement something like it.
> > 
> > I've not looked at it in detail.
> 
> Hi Peter,
> 
> Is something like the untested patch below perhaps what you had in mind?

Most excellent, yes! Now I suppose the $64000 question is if it actually
reduces the amount of storage we use for stack traces..

Seems to boot just fine.. :-)