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    SubjectRe: [PATCH printk v5 1/1] printk: extend console_lock for per-console locking
    On 2022-06-09 14:27:11 [+0200], Jason A. Donenfeld wrote:
    > Hi Dmitry,
    >
    > On Thu, Jun 09, 2022 at 02:18:19PM +0200, Dmitry Vyukov wrote:
    > > > AFAIK, CONFIG_PROVE_RAW_LOCK_NESTING is useful for teasing out cases
    > > > where RT's raw spinlocks will nest wrong with RT's sleeping spinlocks.
    > > > But nobody who wants an RT kernel will be using KFENCE. So this seems
    > > > like a non-issue? Maybe just add a `depends on !KFENCE` to
    > > > PROVE_RAW_LOCK_NESTING?
    > >
    > > Don't know if there are other good solutions (of similar simplicity).
    >
    > Fortunately, I found one that solves things without needing to
    > compromise on anything:
    > https://lore.kernel.org/lkml/20220609121709.12939-1-Jason@zx2c4.com/
    >
    > > Btw, should this new CONFIG_PROVE_RAW_LOCK_NESTING be generally
    > > enabled on testing systems? We don't have it enabled on syzbot.
    >
    > Last time I spoke with RT people about this, the goal was eventually to
    > *always* enable it when lock proving is enabled, but there are too many
    > bugs and cases now to do that, so it's an opt-in. I might be
    > misremembering, though, so CC'ing Sebastian in case he wants to chime
    > in.

    That is basically still the case. If CONFIG_PROVE_RAW_LOCK_NESTING yells
    then there will be yelling on PREEMPT_RT, too. We would like to get
    things fixed ;)

    Without going through this thread, John is looking at printk and printk
    triggers a few of those. That is one of reasons why this is not enabled
    by default.

    > Jason

    Sebastian

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