linux-kernel - Re: [PATCH 2/2] tracing/hist: add modulus operator

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Message-ID: <ZBsFXN/rEG3UJOz1@FVFF77S0Q05N>
Date:   Wed, 22 Mar 2023 13:40:44 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        mhiramat@...nel.org, zanussi@...nel.org
Subject: Re: [PATCH 2/2] tracing/hist: add modulus operator

On Sat, Mar 18, 2023 at 03:19:02PM -0400, Steven Rostedt wrote:
> On Thu,  2 Mar 2023 17:17:55 +0000
> Mark Rutland <mark.rutland@....com> wrote:
> 
> > @@ -436,6 +438,21 @@ static u64 hist_field_mult(struct hist_field *hist_field,
> >  	return val1 * val2;
> >  }
> >  
> > +static u64 hist_field_mod(struct hist_field *hist_field,
> > +			  struct tracing_map_elt *elt,
> > +			  struct trace_buffer *buffer,
> > +			  struct ring_buffer_event *rbe,
> > +			  void *event)
> > +{
> > +	struct hist_field *operand1 = hist_field->operands[0];
> > +	struct hist_field *operand2 = hist_field->operands[1];
> > +
> > +	u64 val1 = hist_fn_call(operand1, elt, buffer, rbe, event);
> > +	u64 val2 = hist_fn_call(operand2, elt, buffer, rbe, event);
> > +
> > +	return val1 % val2;
> 
> Is modulus operations on 64 bit integers valid on 32 bit architectures?
> 
> Don't we need to do something like:
> 
> 	div64_u64_rem(val1, val2, &rem);
> 	return rem;
> 
> ?

Yes, we do; the build bots have also started shouting at me for this.

I'll go fold that in...

Mark.