Re: [PATCH 25/48] rcu: Mark writes to rcu_sync ->gp_count field

Oleg Nesterov
2024-05-12T10:43:26Z

Sorry for another delay...

On 05/10, Paul E. McKenney wrote:
>
> On Fri, May 10, 2024 at 03:50:57PM +0200, Oleg Nesterov wrote:
> >
> > I can only find the strnstr(buf, "rcu") checks in skip_report(),
> > but they only cover the KCSAN_REPORT_VALUE_CHANGE_ONLY case...
>
> Huh, new one on me! When I run KCSAN, I set CONFIG_KCSAN_STRICT=y,
> which implies CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY=n, which should
> prevent skip_report() from even being invoked.
>
> Which suggests that in the rest of the kernel, including "rcu_"
> in your function name gets you stricter KCSAN checking. ;-)

Yes.

And that is why I was very confused. I misinterpreted the "stricter
data-race rules used in RCU code" as if there must be more "rcu-only"
hacks in the kernel/kcsan/ code which I can't find ;)

Oleg.