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 E8D9E541E48; Tue, 22 Sep 2026 16:43:21 +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=1790095403; cv=none; b=Uo1T9Ljtk07sWPYUqGGKI9YYIVOJQLooDqdAHxq7gRZ5UbfpD1x4wp3yUlNjyPgUepFFe0ppVy1zvcsms8lOxCRdWh0AyROBTNTjouN7ZHWskugyGMFSVPheRSCao5BiUB7mdUfSF4xxNiy5OpZCxuIELE3nGLzq8pbVtz7sppk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790095403; c=relaxed/simple; bh=PO9TaFPgtjvbUhCAUWGipQZAobU3eRmmHSpDDVCRDac=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=h1REnji8qBcb7I8VitlhpeTVllGk6+6SCNRZW7fZTksITuKJ23t2ieA5aa85Kpy6Y3wOblay9H/Oc5NdB+ebawOeuMAy+gfttLjy8tFog0ufQVvB1kmXg+3ql5ZKjofUCfddKQXvRcfYVTY7/dKUHSqHFh5ig945dmWa66+qtAk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fhujisoQ; 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="fhujisoQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 203C91F00899; Tue, 22 Sep 2026 16:43:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790095401; bh=Ot8oG0FQtZs6Fvo3vnKvxxIDdhkxVgyKmszzWm92l5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=fhujisoQI4Tt1DieE37r7BLdvvAN82vpwukQGU7OUKmE8oIDr12TNCMpm9XBmCMQL VW4WyLts4XM3OsAydzseH5hUKBN5RotdfECtRjgAprjk8atgn3T2N1gWDIsuFnvjJz ZUisx/5g6xQ/QSQ+7mJTbalUBNgEr7iO2uuFx9bv26eDwu1STSVrvgwTDa2kTwi5pp XjgVqAz5oOiWg9H7pIH/G2r7D8ndkbR8NgDcLgV5pdvLTnB9+dPZq4z1F2jwdukHj6 hdm2MFmrvcoCRYusiA7ikqygU7QuffeOJ+9bw86qE+cNN2unhyy2Lq+4JXFyfIEVes WVDUcy3kTqvZQ== 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 v6 04/12] net/rds: make rds_destroy_pending() report a connection's own destroy Date: Tue, 22 Sep 2026 09:43:10 -0700 Message-Id: <20260922164318.447049-5-achender@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260922164318.447049-1-achender@kernel.org> References: <20260922164318.447049-1-achender@kernel.org> Precedence: bulk X-Mailing-List: linux-rdma@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 - 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. Today every rds_conn_destroy() does happen on one of those two global paths - the last single-connection caller, the protocol-version mismatch in rds_ib_cm_connect_complete(), was turned into a drop by commit f97d8c7bab78 ("rds: ib: use rds_conn_drop() on protocol version mismatch") - so the predicate is currently never wrong. It is also never precise: 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; the passive-twin creation must refuse a parent whose destroy has begun; and a future single-connection destroy - a hot-unplugged IB device, or the asynchronous teardown the Oracle UEK kernel has - would re-open the window below. While a single-connection destroy runs, 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. Additionally, the other requeueing sites can likewise re-arm works that live in the about-to-be-freed connection unless rds_destroy_pending() has something to guard it with. The version-mismatch path used to be covered: commit c90ecbfaf50d2 ("rds: Use atomic flag to track connections being destroyed") introduced the RDS_DESTROY_PENDING cp_flags bit for exactly this, and after commit ebeeb1ad9b8ad ("rds: tcp: use rds_destroy_pending() to synchronize netns/module teardown and rds connection/workq management") it was set right before that rds_conn_destroy() call and tested via rds_ib_is_unloading(). Commit cdc306a5c9cd3 ("rds: make v3.1 as compat version") then removed the last set_bit while leaving the test behind, so the bit has been dead ever since and per-conn destroy has run unguarded. Record the destroy on the connection itself: 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 | 8 ++++++++ net/rds/ib.c | 5 +---- net/rds/rds.h | 12 ++++++++++-- 3 files changed, 19 insertions(+), 6 deletions(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index a96569a3ee9a..242ca0570a47 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -579,6 +579,14 @@ 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 all test rds_destroy_pending() under + * rcu_read_lock()) 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 786f39169bc1..9fe3b9951bd3 100644 --- a/net/rds/ib.c +++ b/net/rds/ib.c @@ -525,10 +525,7 @@ 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..50b08c28ab86 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 +147,14 @@ 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. + */ + bool c_destroy_in_prog; struct rds_connection *c_passive; struct rds_transport *c_trans; @@ -994,7 +1001,8 @@ 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