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 A755017733; Fri, 24 Nov 2023 10:04:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fW/cmt1T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 48068C433C8; Fri, 24 Nov 2023 10:04:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700820251; bh=odyegxK7uxxBKnGsjhd8OdJQcNHKmuTu63nAYxY3t2E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fW/cmt1TnBYSriyoDoMYuXJEjNH09il9ygKQUnnl5ODH1Wr4IfG4Y93l6CbHMIkvU WdRO66wZVI6cOKxPozmzXAtliC+A0SXhgb3rANXFTcpI8DECN74dAXajeWG/4bgXVc hru+IlPXZuZ7As/Yj8pyZCrhdTzKJ9RnHGTzZoZke5XVwMKib7d/xeqhAKRqgrT7U5 r07Hlt5ewNzEZTaxBK/Kqi+BRziZUliGYLT/327vvKele7g2dQpAif2AbkiQg5cQ+9 ffFrzzCmaOUX3wv6lFkFY9+9myZABvN3CxMgW2FTRNEJVgUyifLQObqRDR0enfupJr D5aRl8/ymt0oA== Date: Fri, 24 Nov 2023 15:34:03 +0530 From: Manivannan Sadhasivam To: Qiang Yu Cc: quic_jhugo@quicinc.com, mhi@lists.linux.dev, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, quic_cang@quicinc.com, quic_mrana@quicinc.com Subject: Re: [PATCH v4 2/4] bus: mhi: host: Drop chan lock before queuing buffers Message-ID: <20231124100403.GA4536@thinkpad> References: <1699939661-7385-1-git-send-email-quic_qianyu@quicinc.com> <1699939661-7385-3-git-send-email-quic_qianyu@quicinc.com> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1699939661-7385-3-git-send-email-quic_qianyu@quicinc.com> On Tue, Nov 14, 2023 at 01:27:39PM +0800, Qiang Yu wrote: > Ensure read and write locks for the channel are not taken in succession by > dropping the read lock from parse_xfer_event() such that a callback given > to client can potentially queue buffers and acquire the write lock in that > process. Any queueing of buffers should be done without channel read lock > acquired as it can result in multiple locks and a soft lockup. > Is this patch trying to fix an existing issue in client drivers or a potential issue in the future drivers? Even if you take care of disabled channels, "mhi_event->lock" acquired during mhi_mark_stale_events() can cause deadlock, since event lock is already held by mhi_ev_task(). I'd prefer not to open the window unless this patch is fixing a real issue. - Mani > Signed-off-by: Qiang Yu > --- > drivers/bus/mhi/host/main.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c > index 6c6d253..c4215b0 100644 > --- a/drivers/bus/mhi/host/main.c > +++ b/drivers/bus/mhi/host/main.c > @@ -642,6 +642,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl, > mhi_del_ring_element(mhi_cntrl, tre_ring); > local_rp = tre_ring->rp; > > + read_unlock_bh(&mhi_chan->lock); > + > /* notify client */ > mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result); > > @@ -667,6 +669,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl, > kfree(buf_info->cb_buf); > } > } > + > + read_lock_bh(&mhi_chan->lock); > } > break; > } /* CC_EOT */ > -- > 2.7.4 > > -- மணிவண்ணன் சதாசிவம்