RE: [PATCH] sched: fix integer handling issue

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Tuesday, 22 February 2022 17.03
> 
> On Tue, 22 Feb 2022 15:13:53 +0100
> Morten Brørup <mb@smartsharesystems.com> wrote:
> 
> > > From: Megha Ajmera [mailto:megha.ajmera@intel.com]
> > > Sent: Tuesday, 22 February 2022 14.19
> > >
> > > Masking of core mask was incorrect. Instead of using 1U for
> shifting,
> > > it
> > > should be using 1LU as the result is assigned to uint64.
> > >
> > > CID 375859: Potentially overflowing expression "1U <<
> app_main_core"
> > > with
> > > type "unsigned int" (32 bits, unsigned) is evaluated using 32-bit
> > > arithmetic,
> > > and then used in a context that expects an expression of type
> > > "uint64_t"
> > > (64 bits, unsigned).
> > >
> > > Coverity issue: 375859
> > >
> > > Signed-off-by: Megha Ajmera <megha.ajmera@intel.com>
> > > ---
> > >  examples/qos_sched/args.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/examples/qos_sched/args.c b/examples/qos_sched/args.c
> > > index 10ca7bea61..44f2f5640e 100644
> > > --- a/examples/qos_sched/args.c
> > > +++ b/examples/qos_sched/args.c
> > > @@ -433,7 +433,7 @@ app_parse_args(int argc, char **argv)
> > >  			return -1;
> > >  		}
> > >  	}
> > > -	app_used_core_mask |= 1u << app_main_core;
> > > +	app_used_core_mask |= 1lu << app_main_core;
> >
> > Still wrong on 32 bit platforms, where long unsigned int is still 32
> bits.
> >
> > Use this instead:
> > app_used_core_mask |= RTE_BIT64(app_main_core);
> 
> DPDK now supports > 64 lcores. So all code using/assuming a 64 bit mask
> is broken.
> 

Good point. Is there a TODO-list where such a general review request can be filed, or should we just file it as a system-wide bug in Bugzilla?

Nonetheless, I think this one-line fix should be accepted as a short term solution.

-Morten