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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Thomas Gleixner , Jesper Dangaard Brouer Content-Type: text/plain; charset="UTF-8" Hi Sebastian On Wed, 30 Apr 2025 at 15:48, Sebastian Andrzej Siewior wrote: > > With preemptible softirq and no per-CPU locking in local_bh_disable() on > PREEMPT_RT the consumer can be preempted while a skb is returned. > > Avoid the race by disabling the recycle into the cache on PREEMPT_RT. I am not expert on PREEMPT_RT, but this sounds reasonable. Did you have time to test this at all? There's a kernel module Jesper originally authored to track regressions, which unfortunately isn't upstreamed yet [0]. Any chance you can quickly spin it to get some numbers? [0] https://lore.kernel.org/netdev/20250309084118.3080950-1-almasrymina@google.com/ Cheers /Ilias > > Cc: Jesper Dangaard Brouer > Cc: Ilias Apalodimas > Signed-off-by: Sebastian Andrzej Siewior > --- > net/core/page_pool.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index 7745ad924ae2d..ba8803c2c0b20 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -805,6 +805,10 @@ static bool page_pool_napi_local(const struct page_pool *pool) > const struct napi_struct *napi; > u32 cpuid; > > + /* On PREEMPT_RT the softirq can be preempted by the consumer */ > + if (IS_ENABLED(CONFIG_PREEMPT_RT)) > + return false; > + > if (unlikely(!in_softirq())) > return false; > > -- > 2.49.0 >