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SubjectRe: WARNING: suspicious RCU usage in idtentry_exit
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Dmitry,

Dmitry Vyukov <dvyukov@google.com> writes:
> On Thu, May 28, 2020 at 10:48 PM Paul E. McKenney <paulmck@kernel.org> wrote:
>> On Thu, May 28, 2020 at 10:19:02PM +0200, Thomas Gleixner wrote:
>> OK, from the .config, another suggestion is to build the kernel
>> with CONFIG_RCU_EQS_DEBUG=y. This still requires that this issue be
>> reproduced, but it might catch the problem earlier.
>
> How much does it slow down execution? If we enable it on syzbot, it
> will affect all fuzzing done by syzbot always.
> It can tolerate significant slowdown and it's far from a production
> kernel (it enables KASAN, KCOV, LOCKDEP and more). But I am still
> asking because some debugging features are built without performance
> in mind at all (like let's just drop a global lock in every
> kmalloc/free, which may be too much even for a standard debug build).

It's not worse than lockdep.

Thanks,

tglx

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