From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B759C55162 for ; Thu, 30 Jul 2026 11:19:33 +0000 (UTC) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 3D6AB40274; Thu, 30 Jul 2026 13:19:32 +0200 (CEST) Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by mails.dpdk.org (Postfix) with ESMTP id 684BE40272 for ; Thu, 30 Jul 2026 13:19:31 +0200 (CEST) dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=Z6vAuCJq2ig+0sH954CCHVEmI7EWk97LDg18tngoDjs=; b=4Jf/N5t/khc7Oxu/6NZzSPviUSTjNyy9zBQo0Dx7OmNbFIXDJehkspTVxW7S6yJ4YHesnzNwD k79RQ9BJ2112IS9WGV3yRFWa8R2aUQo3Auz/Ss3vWx4ys24zX/q98PNScTvjVIcdffWusB/DTFi KDgI1rZfs1lwEIRcKdY/t60= Received: from mail.maildlp.com (unknown [172.18.224.83]) by frasgout.his.huawei.com (SkyGuard) with ESMTPS id 4h9mt63jd8zJ46cf; Thu, 30 Jul 2026 19:18:54 +0800 (CST) Received: from frapema500002.china.huawei.com (unknown [7.182.19.148]) by mail.maildlp.com (Postfix) with ESMTPS id 82D4740577; Thu, 30 Jul 2026 19:19:29 +0800 (CST) Received: from frapema500003.china.huawei.com (7.182.19.114) by frapema500002.china.huawei.com (7.182.19.148) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 30 Jul 2026 13:19:29 +0200 Received: from frapema500003.china.huawei.com ([7.182.19.114]) by frapema500003.china.huawei.com ([7.182.19.114]) with mapi id 15.02.1544.011; Thu, 30 Jul 2026 13:19:29 +0200 From: Marat Khalili To: Marat Khalili , Stephen Hemminger , "dev@dpdk.org" CC: Konstantin Ananyev Subject: RE: [RFC 01/32] bpf: replace deprecated SMP barriers with C11 fences Thread-Topic: [RFC 01/32] bpf: replace deprecated SMP barriers with C11 fences Thread-Index: AQHdH4O2ptQbX30vgEiaf+/z/N+qaraFv74wgAAqXcA= Date: Thu, 30 Jul 2026 11:19:28 +0000 Message-ID: References: <20260729175715.165120-1-stephen@networkplumber.org> <20260729175715.165120-2-stephen@networkplumber.org> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.206.138.16] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 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 Gemini's suggestion FWIW (looks sensible but not tested): --- This commit replaces the deprecated DPDK SMP memory barriers in the BPF packet processing module with standard C11 atomic operations.=20 Rather than relying on standalone explicit fences (which can introduce=20 unnecessary overhead and are less idiomatic in C11), this patch=20 embeds the memory ordering directly into the atomic operations: 1. The usage counter (`cbi->use`) now utilizes `rte_atomic_fetch_add_explic= it`. Entering the callback uses `acquire` semantics, and exiting uses `release` semantics, forming a proper lightweight lock without standalon= e fences. 2. The callback pointer (`cbi->cb`) is marked as `RTE_ATOMIC` to prevent=20 data races between the datapath and control path. It is updated=20 and read using explicit atomic loads/stores with `acquire`/`release` sem= antics. --- lib/bpf/bpf_pkt.c | 61 +++++++++++++++++++++++++++-------------------- 1 file changed, 35 insertions(+), 26 deletions(-) diff --git a/lib/bpf/bpf_pkt.c b/lib/bpf/bpf_pkt.c index f072fdaaed..a831b5ad86 100644 --- a/lib/bpf/bpf_pkt.c +++ b/lib/bpf/bpf_pkt.c @@ -30,7 +30,7 @@ struct __rte_cache_aligned bpf_eth_cbi { /* used by both data & control path */ RTE_ATOMIC(uint32_t) use; /*usage counter */ - const struct rte_eth_rxtx_callback *cb; /* callback handle */ + RTE_ATOMIC(const struct rte_eth_rxtx_callback *) cb; /* callback handle = */ struct rte_bpf *bpf; struct rte_bpf_jit jit; /* used by control path only */ @@ -80,9 +80,7 @@ static struct bpf_eth_cbh tx_cbh =3D { static __rte_always_inline void bpf_eth_cbi_inuse(struct bpf_eth_cbi *cbi) { - cbi->use++; - /* make sure no store/load reordering could happen */ - rte_smp_mb(); + rte_atomic_fetch_add_explicit(&cbi->use, 1, rte_memory_order_acquire); } =20 /* @@ -91,9 +89,7 @@ bpf_eth_cbi_inuse(struct bpf_eth_cbi *cbi) static __rte_always_inline void bpf_eth_cbi_unuse(struct bpf_eth_cbi *cbi) { - /* make sure all previous loads are completed */ - rte_smp_rmb(); - cbi->use++; + rte_atomic_fetch_add_explicit(&cbi->use, 1, rte_memory_order_release); } =20 /* @@ -104,15 +100,12 @@ bpf_eth_cbi_wait(const struct bpf_eth_cbi *cbi) { uint32_t puse; =20 - /* make sure all previous loads and stores are completed */ - rte_smp_mb(); - - puse =3D cbi->use; + puse =3D rte_atomic_load_explicit(&cbi->use, rte_memory_order_acquire); =20 /* in use, busy wait till current RX/TX iteration is finished */ if ((puse & BPF_ETH_CBI_INUSE) !=3D 0) { RTE_WAIT_UNTIL_MASKED((__rte_atomic uint32_t *)(uintptr_t)&cbi->use, - UINT32_MAX, !=3D, puse, rte_memory_order_relaxed); + UINT32_MAX, !=3D, puse, rte_memory_order_acquire); } } =20 @@ -201,11 +194,13 @@ bpf_rx_callback_vm(__rte_unused uint16_t port, __rte_= unused uint16_t queue, { struct bpf_eth_cbi *cbi; uint16_t rc; + const struct rte_eth_rxtx_callback *cb; =20 cbi =3D user_param; =20 bpf_eth_cbi_inuse(cbi); - rc =3D (cbi->cb !=3D NULL) ? + cb =3D rte_atomic_load_explicit(&cbi->cb, rte_memory_order_acquire); + rc =3D (cb !=3D NULL) ? pkt_filter_vm(cbi->bpf, pkt, nb_pkts, 1) : nb_pkts; bpf_eth_cbi_unuse(cbi); @@ -219,10 +214,12 @@ bpf_rx_callback_jit(__rte_unused uint16_t port, __rte= _unused uint16_t queue, { struct bpf_eth_cbi *cbi; uint16_t rc; + const struct rte_eth_rxtx_callback *cb; =20 cbi =3D user_param; bpf_eth_cbi_inuse(cbi); - rc =3D (cbi->cb !=3D NULL) ? + cb =3D rte_atomic_load_explicit(&cbi->cb, rte_memory_order_acquire); + rc =3D (cb !=3D NULL) ? pkt_filter_jit(&cbi->jit, pkt, nb_pkts, 1) : nb_pkts; bpf_eth_cbi_unuse(cbi); @@ -236,10 +233,12 @@ bpf_tx_callback_vm(__rte_unused uint16_t port, __rte_= unused uint16_t queue, { struct bpf_eth_cbi *cbi; uint16_t rc; + const struct rte_eth_rxtx_callback *cb; =20 cbi =3D user_param; bpf_eth_cbi_inuse(cbi); - rc =3D (cbi->cb !=3D NULL) ? + cb =3D rte_atomic_load_explicit(&cbi->cb, rte_memory_order_acquire); + rc =3D (cb !=3D NULL) ? pkt_filter_vm(cbi->bpf, pkt, nb_pkts, 0) : nb_pkts; bpf_eth_cbi_unuse(cbi); @@ -253,10 +252,12 @@ bpf_tx_callback_jit(__rte_unused uint16_t port, __rte= _unused uint16_t queue, { struct bpf_eth_cbi *cbi; uint16_t rc; + const struct rte_eth_rxtx_callback *cb; =20 cbi =3D user_param; bpf_eth_cbi_inuse(cbi); - rc =3D (cbi->cb !=3D NULL) ? + cb =3D rte_atomic_load_explicit(&cbi->cb, rte_memory_order_acquire); + rc =3D (cb !=3D NULL) ? pkt_filter_jit(&cbi->jit, pkt, nb_pkts, 0) : nb_pkts; bpf_eth_cbi_unuse(cbi); @@ -274,10 +275,12 @@ bpf_rx_callback_mb_vm(__rte_unused uint16_t port, __r= te_unused uint16_t queue, { struct bpf_eth_cbi *cbi; uint16_t rc; + const struct rte_eth_rxtx_callback *cb; =20 cbi =3D user_param; bpf_eth_cbi_inuse(cbi); - rc =3D (cbi->cb !=3D NULL) ? + cb =3D rte_atomic_load_explicit(&cbi->cb, rte_memory_order_acquire); + rc =3D (cb !=3D NULL) ? pkt_filter_mb_vm(cbi->bpf, pkt, nb_pkts, 1) : nb_pkts; bpf_eth_cbi_unuse(cbi); @@ -292,10 +295,12 @@ bpf_rx_callback_mb_jit(__rte_unused uint16_t port, __= rte_unused uint16_t queue, { struct bpf_eth_cbi *cbi; uint16_t rc; + const struct rte_eth_rxtx_callback *cb; =20 cbi =3D user_param; bpf_eth_cbi_inuse(cbi); - rc =3D (cbi->cb !=3D NULL) ? + cb =3D rte_atomic_load_explicit(&cbi->cb, rte_memory_order_acquire); + rc =3D (cb !=3D NULL) ? pkt_filter_mb_jit(&cbi->jit, pkt, nb_pkts, 1) : nb_pkts; bpf_eth_cbi_unuse(cbi); @@ -309,10 +314,12 @@ bpf_tx_callback_mb_vm(__rte_unused uint16_t port, __r= te_unused uint16_t queue, { struct bpf_eth_cbi *cbi; uint16_t rc; + const struct rte_eth_rxtx_callback *cb; =20 cbi =3D user_param; bpf_eth_cbi_inuse(cbi); - rc =3D (cbi->cb !=3D NULL) ? + cb =3D rte_atomic_load_explicit(&cbi->cb, rte_memory_order_acquire); + rc =3D (cb !=3D NULL) ? pkt_filter_mb_vm(cbi->bpf, pkt, nb_pkts, 0) : nb_pkts; bpf_eth_cbi_unuse(cbi); @@ -326,10 +333,12 @@ bpf_tx_callback_mb_jit(__rte_unused uint16_t port, __= rte_unused uint16_t queue, { struct bpf_eth_cbi *cbi; uint16_t rc; + const struct rte_eth_rxtx_callback *cb; =20 cbi =3D user_param; bpf_eth_cbi_inuse(cbi); - rc =3D (cbi->cb !=3D NULL) ? + cb =3D rte_atomic_load_explicit(&cbi->cb, rte_memory_order_acquire); + rc =3D (cb !=3D NULL) ? pkt_filter_mb_jit(&cbi->jit, pkt, nb_pkts, 0) : nb_pkts; bpf_eth_cbi_unuse(cbi); @@ -382,8 +391,7 @@ static void bpf_eth_cbi_unload(struct bpf_eth_cbi *bc) { /* mark this cbi as empty */ - bc->cb =3D NULL; - rte_smp_mb(); + rte_atomic_store_explicit(&bc->cb, NULL, rte_memory_order_release); =20 /* make sure datapath doesn't use bpf anymore, then destroy bpf */ bpf_eth_cbi_wait(bc); @@ -395,14 +403,17 @@ static void bpf_eth_unload(struct bpf_eth_cbh *cbh, uint16_t port, uint16_t queue) { struct bpf_eth_cbi *bc; + const struct rte_eth_rxtx_callback *cb; =20 bc =3D bpf_eth_cbh_find(cbh, port, queue); - if (bc =3D=3D NULL || bc->cb =3D=3D NULL) + if (bc =3D=3D NULL) + return; + cb =3D rte_atomic_load_explicit(&bc->cb, rte_memory_order_acquire); + if (cb =3D=3D NULL) return; =20 if (cbh->type =3D=3D BPF_ETH_RX) - rte_eth_remove_rx_callback(port, queue, bc->cb); + rte_eth_remove_rx_callback(port, queue, cb); else - rte_eth_remove_tx_callback(port, queue, bc->cb); + rte_eth_remove_tx_callback(port, queue, cb); =20 bpf_eth_cbi_unload(bc); } @@ -439,6 +450,7 @@ bpf_eth_elf_install(struct bpf_eth_cbh *cbh, uint16_t p= ort, uint16_t queue, rte_rx_callback_fn frx; rte_tx_callback_fn ftx; struct rte_bpf_jit jit; + const struct rte_eth_rxtx_callback *cb; =20 frx =3D NULL; ftx =3D NULL; @@ -470,17 +482,18 @@ bpf_eth_elf_install(struct bpf_eth_cbh *cbh, uint16_t= port, uint16_t queue, return -ENOMEM; =20 /* remove old one, if any */ - if (bc->cb !=3D NULL) + if (rte_atomic_load_explicit(&bc->cb, rte_memory_order_acquire) !=3D NULL= ) bpf_eth_unload(cbh, port, queue); =20 bc->bpf =3D bpf; bc->jit =3D jit; =20 if (cbh->type =3D=3D BPF_ETH_RX) - bc->cb =3D rte_eth_add_rx_callback(port, queue, frx, bc); + cb =3D rte_eth_add_rx_callback(port, queue, frx, bc); else - bc->cb =3D rte_eth_add_tx_callback(port, queue, ftx, bc); + cb =3D rte_eth_add_tx_callback(port, queue, ftx, bc); =20 - if (bc->cb =3D=3D NULL) { + rte_atomic_store_explicit(&bc->cb, cb, rte_memory_order_release); + if (cb =3D=3D NULL) { rc =3D -rte_errno; bpf_eth_cbi_cleanup(bc);