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SubjectRe: [PATCH v3 1/3] lockdep: Make LOCKDEP_CROSSRELEASE configs all part of PROVE_LOCKING
On Tue, Aug 22, 2017 at 11:06:03AM +0200, Peter Zijlstra wrote:
> So I did the below little hack, which basically wipes the entire lock
> history when we start a work and thereby disregards/looses the
> dependency on the work 'lock'.
>
> It makes my test box able to boot and build a kernel on XFS, so while I
> see what you're saying (I think), it doesn't appear to instantly show.
>
> Should I run xfstests or something to further verify things are OK? Does
> that need a scratch partition (I keep forgetting how to run that stuff
> :/).
>
> ---
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 66011c9f5df3..de91cdce9460 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -4756,10 +4756,14 @@ void crossrelease_hist_start(enum xhlock_context_t c)
> {
> struct task_struct *cur = current;
>
> - if (cur->xhlocks) {
> - cur->xhlock_idx_hist[c] = cur->xhlock_idx;
> - cur->hist_id_save[c] = cur->hist_id;
> - }
> + if (!cur->xhlocks)
> + return;
> +
> + if (c == XHLOCK_PROC)
> + invalidate_xhlock(&xhlock(cur->xhlock_idx));

We have to detect dependecies if it exists, even in the following case:

oooooooiiiiiiiiiiiiiiiiiii.........
|<- range for commit ->|

where
o: acquisition outside of each work,
i: acquisition inside of each work,

With yours, we can never detect dependecies wrt 'o'.

We have to remove false dependencies if we established them incorrectly.

I will also think it more.

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