From patchwork Wed Feb 28 01:22:45 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ben Greear X-Patchwork-Id: 10246485 X-Patchwork-Delegate: kvalo@adurom.com Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id D2ED060212 for ; Wed, 28 Feb 2018 01:22:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BE9321FE82 for ; Wed, 28 Feb 2018 01:22:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B396C288CE; Wed, 28 Feb 2018 01:22:58 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4A2511FE82 for ; Wed, 28 Feb 2018 01:22:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751878AbeB1BW5 (ORCPT ); Tue, 27 Feb 2018 20:22:57 -0500 Received: from mail2.candelatech.com ([208.74.158.173]:41762 "EHLO mail2.candelatech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751825AbeB1BWx (ORCPT ); Tue, 27 Feb 2018 20:22:53 -0500 Received: from ben-dt3.candelatech.com (firewall.candelatech.com [50.251.239.81]) by mail2.candelatech.com (Postfix) with ESMTP id 860C940A30A; Tue, 27 Feb 2018 17:22:50 -0800 (PST) From: greearb@candelatech.com To: linux-wireless@vger.kernel.org Cc: ath10k@lists.infradead.org, Ben Greear Subject: [RFC] ath10k: Attempt to work around napi_synchronize hang. Date: Tue, 27 Feb 2018 17:22:45 -0800 Message-Id: <1519780965-15292-1-git-send-email-greearb@candelatech.com> X-Mailer: git-send-email 2.4.11 Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Ben Greear Calling napi_disable twice in a row (w/out starting it and/or without having NAPI active leads to deadlock because napi_disable sets NAPI_STATE_SCHED and NAPI_STATE_NPSVC when it returns, as far as I can tell. So, guard this call to napi_disable. I believe the failure case is something like this: rmmod ath10k_pci ath10k_core Firmware crashes before hif_stop is called by the rmmod path The crash handling logic calls hif_stop Then rmmod gets around to calling hif_stop, but spins endlessly in napi_synchronize. I think one way this could happen is that ath10k_stop checks for state != ATH10K_STATE_OFF, but STATE_RESTARTING is also a possibility. That might be how we can have hif_stop called twice without a hif_start in between. --Ben Signed-off-by: Ben Greear --- drivers/net/wireless/ath/ath10k/core.h | 1 + drivers/net/wireless/ath/ath10k/pci.c | 25 +++++++++++++++++++++++-- 2 files changed, 24 insertions(+), 2 deletions(-) diff --git a/drivers/net/wireless/ath/ath10k/core.h b/drivers/net/wireless/ath/ath10k/core.h index 72b4495..c7ba49f 100644 --- a/drivers/net/wireless/ath/ath10k/core.h +++ b/drivers/net/wireless/ath/ath10k/core.h @@ -1205,6 +1205,7 @@ struct ath10k { /* NAPI */ struct net_device napi_dev; struct napi_struct napi; + bool napi_enabled; struct work_struct stop_scan_work; diff --git a/drivers/net/wireless/ath/ath10k/pci.c b/drivers/net/wireless/ath/ath10k/pci.c index 398e413..9131e15 100644 --- a/drivers/net/wireless/ath/ath10k/pci.c +++ b/drivers/net/wireless/ath/ath10k/pci.c @@ -1956,6 +1956,7 @@ static int ath10k_pci_hif_start(struct ath10k *ar) ath10k_dbg(ar, ATH10K_DBG_BOOT, "boot hif start\n"); napi_enable(&ar->napi); + ar->napi_enabled = true; ath10k_pci_irq_enable(ar); ath10k_pci_rx_post(ar); @@ -2086,8 +2087,28 @@ static void ath10k_pci_hif_stop(struct ath10k *ar) ath10k_pci_irq_disable(ar); ath10k_pci_irq_sync(ar); ath10k_pci_flush(ar); - napi_synchronize(&ar->napi); - napi_disable(&ar->napi); + + /* Calling napi_disable twice in a row (w/out starting it and/or without + * having NAPI active leads to deadlock because napi_disable sets + * NAPI_STATE_SCHED and NAPI_STATE_NPSVC when it returns, as far as I + * can tell. So, guard this call to napi_disable. I believe the + * failure case is something like this: + * rmmod ath10k_pci ath10k_core + * Firmware crashes before hif_stop is called by the rmmod path + * The crash handling logic calls hif_stop + * Then rmmod gets around to calling hif_stop, but spins endlessly + * in napi_synchronize. + * + * I think one way this could happen is that ath10k_stop checks + * for state != ATH10K_STATE_OFF, but STATE_RESTARTING is also + * a possibility. That might be how we can have hif_stop called twice + * without a hif_start in between. --Ben + */ + if (ar->napi_enabled) { + napi_synchronize(&ar->napi); + napi_disable(&ar->napi); + ar->napi_enabled = false; + } spin_lock_irqsave(&ar_pci->ps_lock, flags); WARN_ON(ar_pci->ps_wake_refcount > 0);