net: page_pool: Don't recycle into cache on PREEMPT_RT

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.

Cc: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20250512092736.229935-2-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 2b7684865941854660d32b8d1bb00a72fb550563..974f3eef2efaf410d9deec27e3df8fbd201be3f1 100644 (file)
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -839,6 +839,10 @@ 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;