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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45a053a9019sm84661445e9.21.2025.08.11.14.36.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Aug 2025 14:36:42 -0700 (PDT) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger Subject: [RFC 3/6] pdump: fix races in callbacks Date: Mon, 11 Aug 2025 14:35:01 -0700 Message-ID: <20250811213632.16023-4-stephen@networkplumber.org> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250811213632.16023-1-stephen@networkplumber.org> References: <20250811213632.16023-1-stephen@networkplumber.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org The pdump callback can race with other cpu's in the datapath. Handle this by using reference counts and LSB in manner similar to seqcount and bpf code. Signed-off-by: Stephen Hemminger --- lib/pdump/rte_pdump.c | 48 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 46 insertions(+), 2 deletions(-) diff --git a/lib/pdump/rte_pdump.c b/lib/pdump/rte_pdump.c index ba75b828f2..bfd63fa8c2 100644 --- a/lib/pdump/rte_pdump.c +++ b/lib/pdump/rte_pdump.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include "rte_pdump.h" @@ -62,6 +63,7 @@ static struct pdump_rxtx_cbs { const struct rte_bpf *filter; enum pdump_version ver; uint32_t snaplen; + RTE_ATOMIC(uint32_t) use_count; } rx_cbs[RTE_MAX_ETHPORTS][RTE_MAX_QUEUES_PER_PORT], tx_cbs[RTE_MAX_ETHPORTS][RTE_MAX_QUEUES_PER_PORT]; @@ -78,6 +80,36 @@ static struct { const struct rte_memzone *mz; } *pdump_stats; +static void +pdump_cb_wait(struct pdump_rxtx_cbs *cbs) +{ + /* make sure the data loads happens before the use count load */ + rte_atomic_thread_fence(rte_memory_order_acquire); + + /* wait until use_count is even (not in use) */ + RTE_WAIT_UNTIL_MASKED(&cbs->use_count, 1, ==, 0, rte_memory_order_relaxed); +} + +static __rte_always_inline void +pdump_cb_hold(struct pdump_rxtx_cbs *cbs) +{ + uint32_t count = cbs->use_count + 1; + + rte_atomic_store_explicit(&cbs->use_count, count, rte_memory_order_relaxed); + + /* prevent stores after this from happening before the use_count update */ + rte_atomic_thread_fence(rte_memory_order_release); +} + +static __rte_always_inline void +pdump_cb_release(struct pdump_rxtx_cbs *cbs) +{ + uint32_t count = cbs->use_count + 1; + + /* Synchronizes-with the load acquire in pdump_cb_wait */ + rte_atomic_store_explicit(&cbs->use_count, count, rte_memory_order_release); +} + /* Create a clone of mbuf to be placed into ring. */ static void pdump_copy(uint16_t port_id, uint16_t queue, @@ -146,11 +178,14 @@ pdump_rx(uint16_t port, uint16_t queue, struct rte_mbuf **pkts, uint16_t nb_pkts, uint16_t max_pkts __rte_unused, void *user_params) { - const struct pdump_rxtx_cbs *cbs = user_params; + struct pdump_rxtx_cbs *cbs = user_params; struct rte_pdump_stats *stats = &pdump_stats->rx[port][queue]; + pdump_cb_hold(cbs); pdump_copy(port, queue, RTE_PCAPNG_DIRECTION_IN, pkts, nb_pkts, cbs, stats); + pdump_cb_release(cbs); + return nb_pkts; } @@ -158,14 +193,18 @@ static uint16_t pdump_tx(uint16_t port, uint16_t queue, struct rte_mbuf **pkts, uint16_t nb_pkts, void *user_params) { - const struct pdump_rxtx_cbs *cbs = user_params; + struct pdump_rxtx_cbs *cbs = user_params; struct rte_pdump_stats *stats = &pdump_stats->tx[port][queue]; + pdump_cb_hold(cbs); pdump_copy(port, queue, RTE_PCAPNG_DIRECTION_OUT, pkts, nb_pkts, cbs, stats); + pdump_cb_release(cbs); + return nb_pkts; } + static int pdump_register_rx_callbacks(enum pdump_version ver, uint16_t end_q, uint16_t port, uint16_t queue, @@ -186,6 +225,7 @@ pdump_register_rx_callbacks(enum pdump_version ver, port, qid); return -EEXIST; } + cbs->use_count = 0; cbs->ver = ver; cbs->ring = ring; cbs->mp = mp; @@ -218,6 +258,7 @@ pdump_register_rx_callbacks(enum pdump_version ver, -ret); return ret; } + pdump_cb_wait(cbs); cbs->cb = NULL; } } @@ -246,6 +287,7 @@ pdump_register_tx_callbacks(enum pdump_version ver, port, qid); return -EEXIST; } + cbs->use_count = 0; cbs->ver = ver; cbs->ring = ring; cbs->mp = mp; @@ -277,6 +319,8 @@ pdump_register_tx_callbacks(enum pdump_version ver, -ret); return ret; } + + pdump_cb_wait(cbs); cbs->cb = NULL; } } -- 2.47.2