From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-187.mta1.migadu.com (out-187.mta1.migadu.com [95.215.58.187]) (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 899C63E5EC4 for ; Mon, 20 Jul 2026 22:35:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784586931; cv=none; b=VOOlLpZNE+LHE9wJH/9tMS4nsGq2cWFpYhl9A/i10LWUuLv217swavsFrhUJVlkoFUBm3bLU6M48kNnHvkNTr8XsbykfYe6N2gZj9WHpGRqY+br/z+Qf+SKOBNMUvr8eNg24u1dXmmDgr07/R478YTmc+qn6JjCk2oEQkNxiNyI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784586931; c=relaxed/simple; bh=uEt1ZfvOIhSMqFSrDpNNSXy46Xl2tf08xHqmp84nOOI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lH7XioHwDF4YcADNhsvATfe8BAdxtAzFSTOd9AKHtno5qm7nSLhPKFQy0esM1jb1rUOKxWnM3mydKdBLLd0fievmvpGDjmtNHY6OZ3hQj8SylAtgVizIgpsRY42cxQmyGXiWQwra21nF80ukogcf3L2BGnJqzOaR2tZxOH1PvH0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=DsAjVZfr; arc=none smtp.client-ip=95.215.58.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="DsAjVZfr" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784586917; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vAO7nuZkrP3BMOm91ZZdHZhzuQlIkM/mfZwP7l71+Qk=; b=DsAjVZfr469v8pMSmbbGyECgAwBZ3f4GOYlNpIx/ceMvaI47P/pNIi+XKtlb+aZxSmWV6a eScinbjp6saWNc93weSfamlyY/7a3cL+RMyBH/Zx7wgGYi7T5kr0pdbWvIiLR5mFurDTiD /0CY7Ze8Fnt9cZbc4O72ikHV9R6H0c4= Date: Mon, 20 Jul 2026 23:35:07 +0100 Precedence: bulk X-Mailing-List: linux-can@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH can v3] can: gs_usb: fix hardware timestamp state for mixed channels To: Shuangpeng Bai , mkl@pengutronix.de, mailhol@kernel.org Cc: uwu@coelacanthus.name, kees@kernel.org, linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260720184042.1712217-1-shuangpeng.kernel@gmail.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Vadim Fedorenko In-Reply-To: <20260720184042.1712217-1-shuangpeng.kernel@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 20.07.2026 19:40, Shuangpeng Bai wrote: > The hardware timestamp state is shared by struct gs_usb, but > gs_can_open() and gs_can_close() tie its initialization and teardown to > active_channels and to the feature bits of the channel being opened or > closed. > > This is wrong for mixed-channel devices in both directions. If a > non-timestamp channel opens first, a later timestamp-capable channel does > not initialize the shared cyclecounter/timecounter because active_channels > is already non-zero. Timestamp RX then calls timecounter_cyc2time() with > parent->tc.cc unset. > > Conversely, if a timestamp-capable channel opens first and starts the > shared delayed work, then closes while a non-timestamp channel remains > active, disconnect may close the non-timestamp channel last. The old > teardown check skips gs_usb_timestamp_stop() in that case and frees > struct gs_usb while the delayed work timer is still queued. > > Count the number of active timestamp-capable channels instead. Start the > shared timestamp state when the first such channel opens, stop it when the > last such channel closes, and unwind the count if open fails. > > Initialize the shared timestamp lock and delayed work once during probe. > The first timestamp-capable channel may be opened while RX URBs are > already active, so guard the count and timecounter access with the same > lock. Keep the count zero until timecounter_init() completes, and make RX > and delayed work skip the timecounter while the count is zero. > > Fixes: 45dfa45f52e6 ("can: gs_usb: add RX and TX hardware timestamp support") > Cc: stable@vger.kernel.org > Signed-off-by: Shuangpeng Bai > --- > Changes in v3: > - Drop Suggested-by tag. > - Move active_timestamp_channels management into the timestamp init/stop > helpers. > - Protect active_timestamp_channels with tc_lock, and keep it zero until > timecounter_init() has completed. > - Make RX timestamp conversion and the delayed work skip the timecounter > while no timestamp-capable channel is active. > - Initialize the shared timestamp lock and delayed work once during probe. > > Changes in v2: > - Count active timestamp-capable channels instead of tracking only whether > the shared timestamp worker has been started. > - Stop the shared timestamp worker when the last timestamp-capable channel > closes, even if non-timestamp channels remain open. > - Unwind the timestamp-capable channel count on gs_can_open() failures. > > drivers/net/can/usb/gs_usb.c | 81 ++++++++++++++++++++++++------------ > 1 file changed, 54 insertions(+), 27 deletions(-) > > diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c > index ec9a7cbbbc69..be25d82cedcb 100644 > --- a/drivers/net/can/usb/gs_usb.c > +++ b/drivers/net/can/usb/gs_usb.c > @@ -337,6 +337,7 @@ struct gs_usb { > > unsigned int hf_size_rx; > u8 active_channels; > + u8 active_timestamp_channels; > u8 channel_cnt; > > unsigned int pipe_in; > @@ -447,14 +448,20 @@ static void gs_usb_timestamp_work(struct work_struct *work) > { > struct delayed_work *delayed_work = to_delayed_work(work); > struct gs_usb *parent; > + bool active; > > parent = container_of(delayed_work, struct gs_usb, timestamp); > spin_lock_bh(&parent->tc_lock); > - timecounter_read(&parent->tc); > + active = parent->active_timestamp_channels; > + if (active) { > + timecounter_read(&parent->tc); > + active = parent->active_timestamp_channels; > + } > spin_unlock_bh(&parent->tc_lock); > > - schedule_delayed_work(&parent->timestamp, > - GS_USB_TIMESTAMP_WORK_DELAY_SEC * HZ); > + if (active) > + schedule_delayed_work(&parent->timestamp, > + GS_USB_TIMESTAMP_WORK_DELAY_SEC * HZ); > } > > static void gs_usb_skb_set_timestamp(struct gs_can *dev, > @@ -465,6 +472,11 @@ static void gs_usb_skb_set_timestamp(struct gs_can *dev, > u64 ns; > > spin_lock_bh(&parent->tc_lock); > + if (!parent->active_timestamp_channels) { > + spin_unlock_bh(&parent->tc_lock); > + return; > + } > + > ns = timecounter_cyc2time(&parent->tc, timestamp); > spin_unlock_bh(&parent->tc_lock); > > @@ -474,25 +486,40 @@ static void gs_usb_skb_set_timestamp(struct gs_can *dev, > static void gs_usb_timestamp_init(struct gs_usb *parent) > { > struct cyclecounter *cc = &parent->cc; > + bool first = false; > > - cc->read = gs_usb_timestamp_read; > - cc->mask = CYCLECOUNTER_MASK(32); > - cc->shift = 32 - bits_per(NSEC_PER_SEC / GS_USB_TIMESTAMP_TIMER_HZ); > - cc->mult = clocksource_hz2mult(GS_USB_TIMESTAMP_TIMER_HZ, cc->shift); > - > - spin_lock_init(&parent->tc_lock); > spin_lock_bh(&parent->tc_lock); > - timecounter_init(&parent->tc, &parent->cc, ktime_get_real_ns()); > + if (!parent->active_timestamp_channels) { > + cc->read = gs_usb_timestamp_read; > + cc->mask = CYCLECOUNTER_MASK(32); > + cc->shift = 32 - bits_per(NSEC_PER_SEC / > + GS_USB_TIMESTAMP_TIMER_HZ); > + cc->mult = clocksource_hz2mult(GS_USB_TIMESTAMP_TIMER_HZ, > + cc->shift); > + > + timecounter_init(&parent->tc, &parent->cc, > + ktime_get_real_ns()); > + first = true; > + } > + parent->active_timestamp_channels++; > spin_unlock_bh(&parent->tc_lock); > > - INIT_DELAYED_WORK(&parent->timestamp, gs_usb_timestamp_work); > - schedule_delayed_work(&parent->timestamp, > - GS_USB_TIMESTAMP_WORK_DELAY_SEC * HZ); > + if (first) > + schedule_delayed_work(&parent->timestamp, > + GS_USB_TIMESTAMP_WORK_DELAY_SEC * HZ); > } > > static void gs_usb_timestamp_stop(struct gs_usb *parent) > { > - cancel_delayed_work_sync(&parent->timestamp); > + bool last; > + > + spin_lock_bh(&parent->tc_lock); > + parent->active_timestamp_channels--; > + last = !parent->active_timestamp_channels; > + spin_unlock_bh(&parent->tc_lock); > + > + if (last) > + cancel_delayed_work_sync(&parent->timestamp); > } > tc_lock serializes active_timestamp_channels updates, but this work manipulation is not protected. Imagine CPU0 doing gs_usb_timestamp_stop while CPU1 is doing gs_can_open: CPU0 CPU1 gs_usb_timestamp_stop() gs_usb_timestamp_init() spin_lock_bh(&tc_lock); active_timestamp_channels-- last = true spin_unlock_bh(&tc_lock); ... spin_lock_bh(&tc_lock) ... timecounter_init() ... first = true; ... spin_unlock_bh(&tc_lock) ... schedule_delayed_work() cancel_delayed_work_sync() And the device will have no worker while active_timestamp_channels is not 0. I think we have to find another way of synchronization here. > static void gs_update_state(struct gs_can *dev, struct can_frame *cf) > @@ -980,10 +1007,10 @@ static int gs_can_open(struct net_device *netdev) > > can_rx_offload_enable(&dev->offload); > > - if (!parent->active_channels) { > - if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) > - gs_usb_timestamp_init(parent); > + if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) > + gs_usb_timestamp_init(parent); > > + if (!parent->active_channels) { > for (i = 0; i < GS_MAX_RX_URBS; i++) { > u8 *buf; > > @@ -1094,12 +1121,11 @@ static int gs_can_open(struct net_device *netdev) > out_usb_free_urb: > usb_free_urb(urb); > out_usb_kill_anchored_urbs: > - if (!parent->active_channels) { > - usb_kill_anchored_urbs(&parent->rx_submitted); > + if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) > + gs_usb_timestamp_stop(parent); > > - if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) > - gs_usb_timestamp_stop(parent); > - } > + if (!parent->active_channels) > + usb_kill_anchored_urbs(&parent->rx_submitted); > > can_rx_offload_disable(&dev->offload); > close_candev(netdev); > @@ -1152,12 +1178,11 @@ static int gs_can_close(struct net_device *netdev) > > /* Stop polling */ > parent->active_channels--; > - if (!parent->active_channels) { > - usb_kill_anchored_urbs(&parent->rx_submitted); > + if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) > + gs_usb_timestamp_stop(parent); > > - if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) > - gs_usb_timestamp_stop(parent); > - } > + if (!parent->active_channels) > + usb_kill_anchored_urbs(&parent->rx_submitted); > > /* Stop sending URBs */ > usb_kill_anchored_urbs(&dev->tx_submitted); > @@ -1577,6 +1602,8 @@ static int gs_usb_probe(struct usb_interface *intf, > parent->channel_cnt = icount; > > init_usb_anchor(&parent->rx_submitted); > + spin_lock_init(&parent->tc_lock); > + INIT_DELAYED_WORK(&parent->timestamp, gs_usb_timestamp_work); > > usb_set_intfdata(intf, parent); > parent->udev = udev;