Messages in this thread | | | Date | Wed, 25 Nov 2020 15:11:59 -0800 | From | Jakub Kicinski <> | Subject | Re: [PATCH net-next v3 1/2] lockdep: Introduce in_softirq lockdep assert |
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On Tue, 24 Nov 2020 18:49:28 +0800 Yunsheng Lin wrote: > The current semantic for napi_consume_skb() is that caller need > to provide non-zero budget when calling from NAPI context, and > breaking this semantic will cause hard to debug problem, because > _kfree_skb_defer() need to run in atomic context in order to push > the skb to the particular cpu' napi_alloc_cache atomically. > > So add the lockdep_assert_in_softirq() to assert when the running > context is not in_softirq, in_softirq means softirq is serving or > BH is disabled, which has a ambiguous semantics due to the BH > disabled confusion, so add a comment to emphasize that. > > And the softirq context can be interrupted by hard IRQ or NMI > context, lockdep_assert_in_softirq() need to assert about hard > IRQ or NMI context too. > > Suggested-by: Jakub Kicinski <kuba@kernel.org> > Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com> > --- > V3: add comment to emphasize the ambiguous semantics. > --- > include/linux/lockdep.h | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h > index f559487..8d60f46 100644 > --- a/include/linux/lockdep.h > +++ b/include/linux/lockdep.h > @@ -594,6 +594,13 @@ do { \ > this_cpu_read(hardirqs_enabled))); \ > } while (0) > > +/* Much like in_softirq() - semantics are ambiguous, use carefully. */
I've added both of the comments I suggested in the reply to Peter here and applied to net-next.
Thanks for working on this.
> +#define lockdep_assert_in_softirq() \ > +do { \ > + WARN_ON_ONCE(__lockdep_enabled && \ > + (!in_softirq() || in_irq() || in_nmi())); \ > +} while (0)
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