linux-kernel - Re: [PATCH 3/3] livepatch: Cleanup message handling in klp_try_switch

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Message-Id: <20190425033201.GC24416@JAVRIS.in.ibm.com>
Date:   Thu, 25 Apr 2019 09:02:01 +0530
From:   Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Petr Mladek <pmladek@...e.com>, Jiri Kosina <jikos@...nel.org>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] livepatch: Cleanup message handling in
 klp_try_switch_task()

On Wed, Apr 24, 2019 at 08:48:58PM +0200, Miroslav Benes wrote:
> On Wed, 24 Apr 2019, Josh Poimboeuf wrote:
> 
[...]
> > >  	ret = save_stack_trace_tsk_reliable(task, &trace);
> > > -	WARN_ON_ONCE(ret == -ENOSYS);
> > > +	if (ret == -ENOSYS) {
> > > +		if (!enosys_warned) {
> > > +			printk_deferred(KERN_WARNING "%s: save_stack_trace_tsk_reliable() not supported on this architecture.\n",
> > > +					__func__);
> > > +			enosys_warned = 1;
> > > +		}
> > > +		return ret;
> > > +	}
> > 
> > We already have a similar printk in patch 1, so is this warning really
> > needed?
> 
> I don't think so. pr_warn() in klp_enable_patch() should be enough in my 
> opinion.
> 
> However,
> 
> if (ret == -ENOSYS)
> 	return ret;
> 
> would be justified, wouldn't it?
> 

Probably an one line comment on why we return, will be helpful.

-- 
Kamalesh