From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 0F7413ACA4D; Thu, 8 Oct 2026 03:13:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791429218; cv=none; b=drF3p7UYeQcDoXlTJDh4Eh7gKuQ1CJkHbMFoTakchdvNhwmpO6/VkYaIwWTmrCRuPekLKSbioxNlEPLdsz3iYw5fJ5yd1M4ey4PQhaA+knI8m1kzol+N97bgZkfEyXZg5wcvJNlSWXDZ3jUVDlCUDm46qIoAY0cRqqh/HgLuktU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791429218; c=relaxed/simple; bh=CTJoXls1/T/+FhqtfZvkoLG+XqsWnDJ6G8RsvKnxBAE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=A+yXyvj0x1yV2axwaOWUel6Tx2WcysRNEWwyJbKwe4PqIsxTsu7Xw1Dcuyr1JK5ECWVqr5al992vi3W08c11O49BZccz1NSgDjsN6r+btz3BLcSH8I0nXSoQzYjlKtO752Ov0SpELdJsvYbvF/2DX1got5uyKqqu/2Qr+8RbQ1c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DZFmHOxE; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DZFmHOxE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B01A1F0089B; Thu, 8 Oct 2026 03:13:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791429216; bh=I8GtZmx/fyOlV4MKzGc9aEe4kZkn5e58TZkqpxafcMI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DZFmHOxEeN88cdJ32+zY8wp2pCeYV1QWxeCuYPCBy6VhPjn9Y1sxry5HCCT5lt6S/ uY5a7tGfuFQ7MZhJ27c4VH5blo2Jx5iCxZuQ/VFpNQIzNCj/lpjcMYtvnIrAJP6A+2 0qMr40gmO+qH3ybjPu0zdssgxyB39nk0cAitXZy52izMdCL7M0sB20eIblo25oSk/I ZlAYwbs2hcz72aEsBe2ekd6tAh2gY0dhjpg6osm1mZckSkPmPTnbmX/hX4xC4gEdpG oSLnFy7BAJzQE/62jlmoJG5zbQSGeNxL5IiD7bFsP8MzD/WW+BfkpBlO1yanq2QBgH 8JNq432ccs6Sg== From: Allison Henderson To: netdev@vger.kernel.org, linux-rdma@vger.kernel.org, pabeni@redhat.com, edumazet@google.com, kuba@kernel.org, horms@kernel.org Cc: achender@kernel.org Subject: [PATCH net-next v9 05/13] net/rds: make rds_destroy_pending() report a connection's own destroy Date: Wed, 7 Oct 2026 20:13:25 -0700 Message-Id: <20261008031333.1142174-6-achender@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20261008031333.1142174-1-achender@kernel.org> References: <20261008031333.1142174-1-achender@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rds_conn_destroy() cancels the path works and then destroys the per-path workqueue. However, nothing currently stops the work-requeueing sites from queueing new work on the connection while that happens. The existing code would suggest that this protection is supposed to come from rds_destroy_pending(), since all of those sites - apart from the workers' own self-requeues, which the sync cancel in the destroy path already rejects, and the destroy == true rds_conn_path_drop(), which the destroy itself issues and flushes and IB device removal issues ahead of the module exit that destroys the connection - guard the queueing with rds_destroy_pending() under rcu_read_lock() (the last stragglers were converted by the previous patch), and rds_conn_destroy() already issues a synchronize_rcu() after unhashing the connection. But the predicate only tests for the two global teardown cases (netns destruction via check_net(), module unload via ->t_unloading). Because the conn itself lacks any indication that a destroy is in progress, the predicate does not cover the destruction of a single connection outside these two cases. One caller escapes both terms. When the core rds module unloads, rds_conn_exit() runs rds_loop_net_exit() first, and unregistering the pernet operations invokes rds_loop_exit_net() -> rds_loop_kill_conns() -> rds_conn_destroy() for the loopback connections of every network namespace that is still alive: check_net() is true for all of them, and the loop transport's unloading flag is only set afterwards, by rds_loop_exit(). For the duration of those destroys the predicate is false, so a concurrent rds_cong_queue_updates() can still find the connection on the congestion map's m_conn_list (the conn is only removed from it after the paths are torn down) and call queue_delayed_work() on a cp_wq that destroy_workqueue() has already freed. Nothing can exploit that today: every socket pins the rds module, so none exists by the time rds_exit() runs, and the works a connection's own ordered workqueue re-arms are drained by destroy_workqueue(). But the predicate is wrong for those destroys, and the following patches need it to be right. The predicate is also imprecise even where it is true: it answers "is this connection's world going away", not "is this connection being destroyed", and the following patches need the second answer. Once the free is deferred to the last reference, a connection can be handed to rds_conn_destroy() more than once (the IB unload path re-sweeps its list until every connection is gone) and must recognise its own destroy in progress, and the passive-twin creation must refuse a parent whose destroy has begun. The cp_flags bit that once served this purpose, RDS_DESTROY_PENDING from commit c90ecbfaf50d2 ("rds: Use atomic flag to track connections being destroyed"), was only ever set on the IB protocol-version path and lost its last set_bit in commit cdc306a5c9cd3 ("rds: make v3.1 as compat version"); it never covered the loopback path above, which commit c809195f5523 ("rds: clean up loopback rds_connections on netns deletion") added. Record the destroy on the connection itself, where every caller is covered: set conn->c_destroy_in_prog before the unhash + synchronize_rcu() sequence in rds_conn_destroy() and test it first in rds_destroy_pending(). The existing rcu_read_lock() around every check-and-queue site pairs with that synchronize_rcu(): once it returns, every new reader observes the flag and refuses to queue, and anything queued before it is flushed or cancelled by the existing teardown. Drop the now-unreferenced RDS_DESTROY_PENDING bit and its dead test. In the Oracle UEK kernel the equivalent conn->c_destroy_in_prog flag is part of the larger connection refcounting rework ("net/rds: Add krefs to struct rds_connection"), including ("net/rds: Merge uses of conn->c_destroy_in_prog & RDS_DESTROY_PENDING"). This ports the missing pieces of the requeue guard, which stand on their own. Suggested-by: Sharath Srinivasan Assisted-by: Claude-Code:claude-fable-5 Signed-off-by: Allison Henderson --- net/rds/connection.c | 9 +++++++++ net/rds/ib.c | 5 +---- net/rds/rds.h | 17 +++++++++++++++-- 3 files changed, 25 insertions(+), 6 deletions(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index 95ff50f31d1e..97d470242d0f 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -585,6 +585,15 @@ void rds_conn_destroy(struct rds_connection *conn) "%pI4\n", conn, &conn->c_laddr, &conn->c_faddr); + /* Make rds_destroy_pending() true for this conn. Together with + * the synchronize_rcu() below this stops the work-requeueing + * sites (which test rds_destroy_pending() under rcu_read_lock(), + * bar the exemptions noted at c_destroy_in_prog) from queueing + * new work on the path workqueues once we start cancelling and + * destroying them. + */ + WRITE_ONCE(conn->c_destroy_in_prog, true); + /* Ensure conn will not be scheduled for reconnect */ spin_lock_irq(&rds_conn_lock); hlist_del_init_rcu(&conn->c_hash_node); diff --git a/net/rds/ib.c b/net/rds/ib.c index a7647ec01a11..d9879b6129e7 100644 --- a/net/rds/ib.c +++ b/net/rds/ib.c @@ -528,10 +528,7 @@ static void rds_ib_set_unloading(void) static bool rds_ib_is_unloading(struct rds_connection *conn) { - struct rds_conn_path *cp = &conn->c_path[0]; - - return (test_bit(RDS_DESTROY_PENDING, &cp->cp_flags) || - atomic_read(&rds_ib_unloading) != 0); + return atomic_read(&rds_ib_unloading) != 0; } void rds_ib_exit(void) diff --git a/net/rds/rds.h b/net/rds/rds.h index 2db49573dacd..5afdf5a8d93f 100644 --- a/net/rds/rds.h +++ b/net/rds/rds.h @@ -89,7 +89,6 @@ enum { #define RDS_RECONNECT_PENDING 1 #define RDS_IN_XMIT 2 #define RDS_RECV_REFILL 3 -#define RDS_DESTROY_PENDING 4 /* Max number of multipaths per RDS connection. Must be a power of 2 */ #define RDS_MPATH_WORKERS 8 @@ -148,6 +147,19 @@ struct rds_connection { c_pad_to_32:29; int c_npaths; bool c_with_sport_idx; + /* Set once, by rds_conn_destroy(), before it cancels the path + * works; read through rds_destroy_pending(). A site that arms + * a path work must test the predicate and queue the work inside + * one rcu_read_lock() section: the synchronize_rcu() that + * follows the store is what keeps a queue issued after the + * cancellation from landing on a destroyed workqueue. Two kinds + * of site are exempt: the workers' own self-requeues, which the + * sync cancel in the destroy path rejects, and the destroy == true + * rds_conn_path_drop(): the destroy issues and flushes it itself, + * and IB device removal issues it ahead of the module exit, which + * destroys - and so flushes - that connection afterwards. + */ + bool c_destroy_in_prog; struct rds_connection *c_passive; struct rds_transport *c_trans; @@ -994,7 +1006,8 @@ void __rds_put_mr_final(struct kref *kref); static inline bool rds_destroy_pending(struct rds_connection *conn) { - return !check_net(rds_conn_net(conn)) || + return READ_ONCE(conn->c_destroy_in_prog) || + !check_net(rds_conn_net(conn)) || (conn->c_trans->t_unloading && conn->c_trans->t_unloading(conn)); } -- 2.25.1