From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 ACDE114AD15; Tue, 20 Feb 2024 21:14:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708463672; cv=none; b=h/c3i9ulIkB271spG2mh1klTk2QiV5YhFk6oLbGdiRDPolCCG3/10POJV2dCXcdL7qFHoMfFU93LSwOPto1AxcK5pxam96FzV80gLLjMtRbGT+p2tFKcDt9s8jktLDfLNoFGJitP3x8kOZc4iTShkAMYu9wYaC9VmWmiTckZAIc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708463672; c=relaxed/simple; bh=2PRZuZPUOvEhhILWuCrRF6gUiArF7CU7T71AGEl8rxE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=n4zfJKMFy5sqVZacc1SwvF3Qe7inVNyBofSVmSfaBslKxrrRVrQnftn5AIhADSgHBJ6T5HnlEDMi0SL6WMX+at1PpBv0pQw7hz3ivA7h3+QYOgr2VgtA21RjZ17Be328X0EY/xl66raK18CakJ8VxEX+sUd82o1ehcbU3zOVZkI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=wcCJXBcE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="wcCJXBcE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9B1AC433F1; Tue, 20 Feb 2024 21:14:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708463672; bh=2PRZuZPUOvEhhILWuCrRF6gUiArF7CU7T71AGEl8rxE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wcCJXBcERfRaQqjo7ZAj+pZiwq+D+XWiMG+R5a34RgEY9fBvjq1o3wldG+EO0mQCY 2fQ7zv6N6zRJBbEt/mtlIjDD7Z3RWb9WkBrB200Iz1qn3bnJ7Ml7wfH+ReAnVgOibT YQHescqBr3/27m29BnrELraDxSed7gJIX+MvOpn4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Xu Yang , Saravana Kannan , Sasha Levin Subject: [PATCH 6.6 088/331] driver core: fw_devlink: Improve detection of overlapping cycles Date: Tue, 20 Feb 2024 21:53:24 +0100 Message-ID: <20240220205640.355998217@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240220205637.572693592@linuxfoundation.org> References: <20240220205637.572693592@linuxfoundation.org> User-Agent: quilt/0.67 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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Saravana Kannan [ Upstream commit 6442d79d880cf7a2fff18779265d657fef0cce4c ] fw_devlink can detect most overlapping/intersecting cycles. However it was missing a few corner cases because of an incorrect optimization logic that tries to avoid repeating cycle detection for devices that are already marked as part of a cycle. Here's an example provided by Xu Yang (edited for clarity): usb +-----+ tcpc | | +-----+ | +--| | |----------->|EP| |--+ | | +--| |EP|<-----------| | |--+ | | B | | | +-----+ | A | | +-----+ | ^ +-----+ | | | | | +-----| C |<--+ | | +-----+ usb-phy Node A (tcpc) will be populated as device 1-0050. Node B (usb) will be populated as device 38100000.usb. Node C (usb-phy) will be populated as device 381f0040.usb-phy. The description below uses the notation: consumer --> supplier child ==> parent 1. Node C is populated as device C. No cycles detected because cycle detection is only run when a fwnode link is converted to a device link. 2. Node B is populated as device B. As we convert B --> C into a device link we run cycle detection and find and mark the device link/fwnode link cycle: C--> A --> B.EP ==> B --> C 3. Node A is populated as device A. As we convert C --> A into a device link, we see it's already part of a cycle (from step 2) and don't run cycle detection. Thus we miss detecting the cycle: A --> B.EP ==> B --> A.EP ==> A Looking at it another way, A depends on B in one way: A --> B.EP ==> B But B depends on A in two ways and we only detect the first: B --> C --> A B --> A.EP ==> A To detect both of these, we remove the incorrect optimization attempt in step 3 and run cycle detection even if the fwnode link from which the device link is being created has already been marked as part of a cycle. Reported-by: Xu Yang Closes: https://lore.kernel.org/lkml/DU2PR04MB8822693748725F85DC0CB86C8C792@DU2PR04MB8822.eurprd04.prod.outlook.com/ Fixes: 3fb16866b51d ("driver core: fw_devlink: Make cycle detection more robust") Signed-off-by: Saravana Kannan Tested-by: Xu Yang Link: https://lore.kernel.org/r/20240202095636.868578-3-saravanak@google.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/base/core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index a81bc8844a8f..2cc0ab854168 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -2059,9 +2059,14 @@ static int fw_devlink_create_devlink(struct device *con, /* * SYNC_STATE_ONLY device links don't block probing and supports cycles. - * So cycle detection isn't necessary and shouldn't be done. + * So, one might expect that cycle detection isn't necessary for them. + * However, if the device link was marked as SYNC_STATE_ONLY because + * it's part of a cycle, then we still need to do cycle detection. This + * is because the consumer and supplier might be part of multiple cycles + * and we need to detect all those cycles. */ - if (!(flags & DL_FLAG_SYNC_STATE_ONLY)) { + if (!device_link_flag_is_sync_state_only(flags) || + flags & DL_FLAG_CYCLE) { device_links_write_lock(); if (__fw_devlink_relax_cycles(con, sup_handle)) { __fwnode_link_cycle(link); -- 2.43.0