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net: page_pool: avoid false positive warning if NAPI was never added

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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>
This commit is contained in:
Jakub Kicinski 2025-02-06 14:56:37 -08:00
parent 3e7efc3f4f
commit c1e00bc4be
2 changed files with 14 additions and 5 deletions
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12
net/core/dev.h
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@ -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

7
net/core/page_pool.c
View File

@ -26,6 +26,7 @@
#include <trace/events/page_pool.h>
#include "dev.h"
#include "mp_dmabuf_devmem.h"
#include "netmem_priv.h"
#include "page_pool_priv.h"
@ -1147,11 +1148,7 @@ 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);