linux-kernel - Re: [PATCH V2 9/9] jump_label: Batch up if arch supports it

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Date:   Tue, 18 Dec 2018 22:06:06 +0100
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Zhou Chengming <zhouchengming1@...wei.com>,
        Jiri Kosina <jkosina@...e.cz>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Chris von Recklinghausen <crecklin@...hat.com>,
        Jason Baron <jbaron@...mai.com>, Scott Wood <swood@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Clark Williams <williams@...hat.com>, x86@...nel.org
Subject: Re: [PATCH V2 9/9] jump_label: Batch up if arch supports it

On 12/18/18 9:32 PM, Steven Rostedt wrote:
> Where? Mostly we have BUILD_BUG_ON() which isn't bad at all.
> 
> The only other BUG I see in the jump label code is in the arch specific
> code and that's from 2012. Lately, we are trying to get rid of BUG()
> and panic() entirely, with a few exceptions (where there's really no
> way to return. Like when the function graph stack is corrupted, and we
> don't know where to go).
> 
> If there's a way to continue in a critical state, it's best to WARN()
> and continue on. That way, the user can have a chance to see what
> happened.

Got it!

>> What I could do here is:
>>
>> Add a "fallback" boll that is disabled by default.
>> If I hit this case:
>> 	WARN()
>> 	turn "fallback" on, returning to the old mode (without batch)
>>
>> Sound better?
> Yes, please do.

ack!

Thanks, Steve!

-- Daniel