linux-kernel - Re: [RFC PATCH ghak10 v6 1/2] timekeeping: Audit clock adjustments

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Date:   Thu, 28 Mar 2019 01:10:50 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ondrej Mosnacek <omosnace@...hat.com>
cc:     linux-audit@...hat.com, Paul Moore <paul@...l-moore.com>,
        Richard Guy Briggs <rgb@...hat.com>,
        Steve Grubb <sgrubb@...hat.com>,
        Miroslav Lichvar <mlichvar@...hat.com>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Clark Williams <williams@...hat.com>
Subject: Re: [RFC PATCH ghak10 v6 1/2] timekeeping: Audit clock adjustments

On Thu, 28 Mar 2019, Thomas Gleixner wrote:
> On Thu, 7 Mar 2019, Ondrej Mosnacek wrote:
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -2512,6 +2512,14 @@ void __audit_fanotify(unsigned int response)
> >  		AUDIT_FANOTIFY,	"resp=%u", response);
> >  }
> >  
> > +/* We need to allocate with GFP_ATOMIC here, since these two functions will be
> > + * called while holding the timekeeping lock: */
> 
> Audit is no justification for doing ATOMIC allocations just because it's
> convenient in the middle of code which blocks every concurrent reader. 

Aside of that you might talk to your colleagues working on Preempt-RT about
this. I'm pretty sure they are going to have opinions simply because you
cannot do ATOMIC allocations in those contexts on RT.

Logging needs to be unintrusive and allocations are definitely not.

Thanks,

	tglx