From: Jakub Kicinski kuba@kernel.org
[ Upstream commit c1e00bc4be06cacee6307cedb9b55bbaddb5044d ]
We expect NAPI to be in disabled state when page pool is torn down. But it is also legal if the NAPI is completely uninitialized.
Reviewed-by: Mina Almasry almasrymina@google.com Link: https://patch.msgid.link/20250206225638.1387810-4-kuba@kernel.org Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/dev.h | 12 ++++++++++++ net/core/page_pool.c | 7 ++----- 2 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/net/core/dev.h b/net/core/dev.h index a5b166bbd169a..caa13e431a6bc 100644 --- a/net/core/dev.h +++ b/net/core/dev.h @@ -299,6 +299,18 @@ void xdp_do_check_flushed(struct napi_struct *napi); static inline void xdp_do_check_flushed(struct napi_struct *napi) { } #endif
+/* Best effort check that NAPI is not idle (can't be scheduled to run) */ +static inline void napi_assert_will_not_race(const struct napi_struct *napi) +{ + /* uninitialized instance, can't race */ + if (!napi->poll_list.next) + return; + + /* SCHED bit is set on disabled instances */ + WARN_ON(!test_bit(NAPI_STATE_SCHED, &napi->state)); + WARN_ON(READ_ONCE(napi->list_owner) != -1); +} + void kick_defer_list_purge(struct softnet_data *sd, unsigned int cpu);
#define XMIT_RECURSION_LIMIT 8 diff --git a/net/core/page_pool.c b/net/core/page_pool.c index ede82c610936e..cca51aa2e876f 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -25,6 +25,7 @@
#include <trace/events/page_pool.h>
+#include "dev.h" #include "mp_dmabuf_devmem.h" #include "netmem_priv.h" #include "page_pool_priv.h" @@ -1146,11 +1147,7 @@ void page_pool_disable_direct_recycling(struct page_pool *pool) if (!pool->p.napi) return;
- /* To avoid races with recycling and additional barriers make sure - * pool and NAPI are unlinked when NAPI is disabled. - */ - WARN_ON(!test_bit(NAPI_STATE_SCHED, &pool->p.napi->state)); - WARN_ON(READ_ONCE(pool->p.napi->list_owner) != -1); + napi_assert_will_not_race(pool->p.napi);
mutex_lock(&page_pools_lock); WRITE_ONCE(pool->p.napi, NULL);