From patchwork Fri Jan 17 10:18:12 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Hou Tao X-Patchwork-Id: 13943109 X-Patchwork-Delegate: bpf@iogearbox.net Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0B3A1FC118 for ; Fri, 17 Jan 2025 10:06:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737108376; cv=none; b=ecy5b4tUhLiI58yEHygvFLOPLcVD/cj9ftFb0fT+H0YgiAroDZ0c59X8saDnJsP4GQyNFOpR1HqJq8zhB7NAqnMTkgZ6RI/maTwExrOBFdPOqP3Kb0flH1lPQPiKVPQD6SoJjTKg4xZjDnO6QvFb50kV+cNmZxLdOhg660wEYq8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737108376; c=relaxed/simple; bh=6o10SZRDc5p07gjMhZv7/S2ZOo9knqa4RQ2yI/MOSN0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=qmhnFuIZkMgWaEVmTIWWMfs1zzRC3/gusRRpr70274LjdnTja0XKQTYDCr9ugTbK2kqwL7TT5mIccJ4FNSpszxZAs8Ovw8+lVGbMNBpZx7SN4uRNZwnHBE+l5m0eCtrLmFkPESAMgZoq8F+b2rmQTS2ld15abTvb2b4U+3KRJsQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4YZFjm73KDz4f3lVX for ; Fri, 17 Jan 2025 18:05:48 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id ACD191A1A2A for ; Fri, 17 Jan 2025 18:06:10 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.124.27]) by APP4 (Coremail) with SMTP id gCh0CgBHrGCNK4pnQRDPBA--.48008S5; Fri, 17 Jan 2025 18:06:10 +0800 (CST) From: Hou Tao To: bpf@vger.kernel.org Cc: Martin KaFai Lau , Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Song Liu , Hao Luo , Yonghong Song , Daniel Borkmann , KP Singh , Stanislav Fomichev , Jiri Olsa , John Fastabend , Sebastian Andrzej Siewior , houtao1@huawei.com, xukuohai@huawei.com Subject: [PATCH bpf-next v3 1/5] bpf: Free special fields after unlock in htab_lru_map_delete_node() Date: Fri, 17 Jan 2025 18:18:12 +0800 Message-Id: <20250117101816.2101857-2-houtao@huaweicloud.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20250117101816.2101857-1-houtao@huaweicloud.com> References: <20250117101816.2101857-1-houtao@huaweicloud.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: gCh0CgBHrGCNK4pnQRDPBA--.48008S5 X-Coremail-Antispam: 1UD129KBjvJXoW7uF4UXw17Jr45WF4fJr4xJFb_yoW8XrWkpa n3Gay3Gw18Zr1q9a95tF4vgry5Cw4fGw47Kry8GFyFy3W3XasFgw4aqryftFyaqrWkArna vrZYqry5tryUCrDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPFb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUGw A2048vs2IY020Ec7CjxVAFwI0_Gr0_Xr1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxS w2x7M28EF7xvwVC0I7IYx2IY67AKxVW5JVW7JwA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxV W8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMc Ij6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_ Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7CjxVAaw2AFwI 0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG 67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r4a6rW5MI IYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E 14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJV W8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjxU2HGQ DUUUU X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-Patchwork-Delegate: bpf@iogearbox.net From: Hou Tao When bpf_timer is used in LRU hash map, calling check_and_free_fields() in htab_lru_map_delete_node() will invoke bpf_timer_cancel_and_free() to free the bpf_timer. If the timer is running on other CPUs, hrtimer_cancel() will invoke hrtimer_cancel_wait_running() to spin on current CPU to wait for the completion of the hrtimer callback. Considering that the deletion has already acquired a raw-spin-lock (bucket lock). To reduce the time holding the bucket lock, move the invocation of check_and_free_fields() out of bucket lock. However, because htab_lru_map_delete_node() is invoked with LRU raw spin lock being held, the freeing of special fields still happens in a locked scope. Signed-off-by: Hou Tao Reviewed-by: Toke Høiland-Jørgensen --- kernel/bpf/hashtab.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 40095dda891d3..963cccb01daae 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -824,13 +824,14 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node) hlist_nulls_for_each_entry_rcu(l, n, head, hash_node) if (l == tgt_l) { hlist_nulls_del_rcu(&l->hash_node); - check_and_free_fields(htab, l); bpf_map_dec_elem_count(&htab->map); break; } htab_unlock_bucket(htab, b, tgt_l->hash, flags); + if (l == tgt_l) + check_and_free_fields(htab, l); return l == tgt_l; }