linux-kernel - Re: [PATCH 3/3] compiler: inline does not imply notrace

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Date:   Tue, 29 Nov 2022 18:02:01 +0000
From:   Nadav Amit <namit@...are.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     Peter Zijlstra <peterz@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        "linux-um@...ts.infradead.org" <linux-um@...ts.infradead.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        X86 ML <x86@...nel.org>, Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 3/3] compiler: inline does not imply notrace

On Nov 29, 2022, at 7:06 AM, Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 29 Nov 2022 04:25:38 +0000
> Nadav Amit <namit@...are.com> wrote:
> 
> 
>> I will need to further debug it, but this issue does not occur every time.
>> 
>> The kernel didn’t crash exactly - it’s more of a deadlock. I have lockdep
>> enabled, so it is not a deadlock that lockdep knows. Could it be that
>> somehow things just slowed down due to IPIs and mostly-disabled IRQs? I have
>> no idea. I would need to recreate the scenario. 
> 
> You have lockdep enabled and you are running function tracing with stack
> trace on? So you are doing a stack trace on *every* function that is traced?
> 
> I don't think you hit a deadlock, I think you hit a live lock. You could
> possibly slow the system down so much that when an interrupt finishes it's
> time for it to be triggered again, and you never make forward progress.

It might be the issue. Perhaps I have a bug, because my code was supposed to
either enable stack-tracing with selected functions or create a trace all
function but *without* stack-tracing.

Thanks for the pointer and sorry for the noise.

Regards,
Nadav