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 C2CC837A856; Sat, 12 Sep 2026 19:15:23 +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=1789240524; cv=none; b=fwcaNmDqHetD7JiqcHIfEhrZGR/cjn4v1/zViB+d0PcSrjYVagKKtM1SU1EchEZrUy7uzu/sUH0vYys1DloINYv6BFQi/CWAHYXMrGB8/9UVA0wa6F7BFEMu0qtQhAWFR0WThN5FRGYRvR0ry78StijBNz3WCoOF2CltcO182rw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789240524; c=relaxed/simple; bh=aOpmqcVvf4aXGygytZ9dZkgcMj13kOzVknGdo5HOpDc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mkcCQINM/e3DSBd5aYJZkE2/h37f5Z+U0FndmoICdvv0r9swqIjj49Nhc8mOnGE5uXaZsRgJRlIiFumrXixCuNkwJjey3jIEzeQAJAJcOF42NOZuq0hmLSq3PXYk5lxJ9BHC/B9Xmdx1l43qcp6uxB6Oc7/50Y93UIbOpxbPRDM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Q5dr3Mgn; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Q5dr3Mgn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 246E21F000FF; Sat, 12 Sep 2026 19:15:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789240523; bh=BoN9TE4zomR/hdGAT1unB0VptyPj6KA/6HJTe8RYqco=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Q5dr3MgnOJM+bDqR3MIiJ21F4+FZDEgA+gNHvlzizahbC+2574hLWMjVZmM9w4Y8b Xe6SOpw7RJNoGsz8SYMOU5IlKVgde2HVQHiotCXfvzf8hV4HDFOyYzqv4VYy7oqj5v 72HNCB7vCKca2di1ExPYXrHAhR0Y7ojyRDwyj9Wc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Allison Henderson , Simon Horman , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 886/935] net/rds: use wq_has_sleeper() in rds_cong_map_updated() Date: Sat, 12 Sep 2026 09:05:16 +0200 Message-ID: <20260912065547.134858915@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065526.833703348@linuxfoundation.org> References: <20260912065526.833703348@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Allison Henderson [ Upstream commit d4f484661961636eb90d287050959e613795f73a ] rds_cong_map_updated() runs after a peer's congestion map has been rewritten (by rds_tcp_cong_recv() and rds_ib_cong_recv(), or the clear-all in the loopback and IB send-completion paths). It bumps rds_cong_generation and then checks waitqueue_active() on map->m_waitq and on rds_poll_waitq to decide whether anyone needs waking. atomic_inc() carries no ordering and waitqueue_active() is a plain load, so nothing orders the map and generation stores before the wait queue reads. The waiters do the mirror image: rds_cong_wait() adds itself to m_waitq and then tests the port bit, and rds_poll() registers on rds_poll_waitq and then reads the generation. That is the store-buffering pattern described above waitqueue_active() in include/linux/wait.h - the updater can observe an empty wait queue while the waiter still observes the port as congested, and no wake-up is issued. rds_cong_wait() is an interruptible sleep with no timeout, so a sender blocked on a congested port stays blocked until the next congestion update from that peer arrives or a signal is delivered. A poll() waiter misses the map-updated notification the same way. Use wq_has_sleeper(), which is waitqueue_active() preceded by the required full barrier, as rds_tcp_state_change() already does for the same pattern. Fixes: 922cb17a5c81 ("RDS: Congestion-handling code") Signed-off-by: Allison Henderson Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260822052647.88318-1-achender@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/rds/cong.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/rds/cong.c b/net/rds/cong.c index 8b689ebbd5b52..c85af56e42e73 100644 --- a/net/rds/cong.c +++ b/net/rds/cong.c @@ -256,9 +256,9 @@ void rds_cong_map_updated(struct rds_cong_map *map, uint64_t portmask) map, &map->m_addr); rds_stats_inc(s_cong_update_received); atomic_inc(&rds_cong_generation); - if (waitqueue_active(&map->m_waitq)) + if (wq_has_sleeper(&map->m_waitq)) wake_up(&map->m_waitq); - if (waitqueue_active(&rds_poll_waitq)) + if (wq_has_sleeper(&rds_poll_waitq)) wake_up_all(&rds_poll_waitq); if (portmask && !list_empty(&rds_cong_monitor)) { -- 2.53.0