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SubjectRe: [PATCH] lib/flex_proportions.c: Remove local_irq_ops in fprop_new_period()
On Sat 04-06-22 21:15:02, wuchi wrote:
> The commit <e78d4833c03e28> (lib: Fix possible deadlock in flexible
> proportion code) adds the local_irq_ops because percpu_counter_{sum
> |add} ops'lock can cause deadlock by interrupts. Now percpu_counter
> _{sum|add} ops use raw_spin_(un)lock_irq*, so revert the commit and
> resolve the conflict.
>
> Signed-off-by: wuchi <wuchi.zero@gmail.com>

Yes, good point. Thanks for cleaning this up. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

I guess Andrew will pickup this patch, or should I do it Andrew?

Honza

> ---
> lib/flex_proportions.c | 10 ++--------
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
> index 53e7eb1dd76c..05cccbcf1661 100644
> --- a/lib/flex_proportions.c
> +++ b/lib/flex_proportions.c
> @@ -63,18 +63,13 @@ void fprop_global_destroy(struct fprop_global *p)
> */
> bool fprop_new_period(struct fprop_global *p, int periods)
> {
> - s64 events;
> - unsigned long flags;
> + s64 events = percpu_counter_sum(&p->events);
>
> - local_irq_save(flags);
> - events = percpu_counter_sum(&p->events);
> /*
> * Don't do anything if there are no events.
> */
> - if (events <= 1) {
> - local_irq_restore(flags);
> + if (events <= 1)
> return false;
> - }
> write_seqcount_begin(&p->sequence);
> if (periods < 64)
> events -= events >> periods;
> @@ -82,7 +77,6 @@ bool fprop_new_period(struct fprop_global *p, int periods)
> percpu_counter_add(&p->events, -events);
> p->period += periods;
> write_seqcount_end(&p->sequence);
> - local_irq_restore(flags);
>
> return true;
> }
> --
> 2.20.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR

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