From nobody Mon May 11 02:57:21 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A2E5C433F5 for ; Sun, 17 Apr 2022 13:54:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234223AbiDQN5E (ORCPT ); Sun, 17 Apr 2022 09:57:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229496AbiDQN5B (ORCPT ); Sun, 17 Apr 2022 09:57:01 -0400 Received: from zju.edu.cn (spam.zju.edu.cn [61.164.42.155]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 894311EEC9 for ; Sun, 17 Apr 2022 06:54:24 -0700 (PDT) Received: from ubuntu.localdomain (unknown [10.15.192.164]) by mail-app2 (Coremail) with SMTP id by_KCgDnFMX_G1xiKCbwAQ--.34781S2; Sun, 17 Apr 2022 21:54:11 +0800 (CST) From: Duoming Zhou To: linux-kernel@vger.kernel.org Cc: gregkh@linuxfoundation.org, davem@davemloft.net, alexander.deucher@amd.com, akpm@linux-foundation.org, broonie@kernel.org, linux-staging@lists.linux.dev, Duoming Zhou Subject: [PATCH] drivers: staging: rtl8192u: Fix deadlock in ieee80211_beacons_stop() Date: Sun, 17 Apr 2022 21:54:07 +0800 Message-Id: <20220417135407.109536-1-duoming@zju.edu.cn> X-Mailer: git-send-email 2.17.1 X-CM-TRANSID: by_KCgDnFMX_G1xiKCbwAQ--.34781S2 X-Coremail-Antispam: 1UD129KBjvJXoW7AFWkKF1DGFWrtw43CrWfZrb_yoW8WrWkpF WDWa4YkF1jvr48u348Gw4kZasxCw4UX34vv34fG395ZanYqFnxWF1vkrW7JF4rAFWDJa43 Zrn5ZrW3Z3WqkrJanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkI1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVWxJr0_GcWl84ACjcxK6I8E 87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_GcCE3s1le2I262IYc4CY6c 8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_ Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwI xGrwACjI8F5VA0II8E6IAqYI8I648v4I1l42xK82IYc2Ij64vIr41l42xK82IY6x8ErcxF aVAv8VW8uw4UJr1UMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr 4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxG rwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVWUJVW8Jw CI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2 z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7VUbXdbUUUUUU== X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/1tbiAgoDAVZdtZOq7gAPss Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" There is a deadlock in ieee80211_beacons_stop(), which is shown below: (Thread 1) | (Thread 2) | ieee80211_send_beacon() ieee80211_beacons_stop() | mod_timer() spin_lock_irqsave() //(1) | (wait a time) ... | ieee80211_send_beacon_cb() del_timer_sync() | spin_lock_irqsave() //(2) (wait timer to stop) | ... We hold ieee->beacon_lock in position (1) of thread 1 and use del_timer_sync() to wait timer to stop, but timer handler also need ieee->beacon_lock in position (2) of thread 2. As a result, ieee80211_beacons_stop() will block forever. This patch extracts del_timer_sync() from the protection of spin_lock_irqsave(), which could let timer handler to obtain the needed lock. Signed-off-by: Duoming Zhou --- drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c b/drive= rs/staging/rtl8192u/ieee80211/ieee80211_softmac.c index 1a43979939a..79f3fbe2555 100644 --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c @@ -528,9 +528,9 @@ static void ieee80211_beacons_stop(struct ieee80211_dev= ice *ieee) spin_lock_irqsave(&ieee->beacon_lock, flags); =20 ieee->beacon_txing =3D 0; - del_timer_sync(&ieee->beacon_timer); =20 spin_unlock_irqrestore(&ieee->beacon_lock, flags); + del_timer_sync(&ieee->beacon_timer); } =20 void ieee80211_stop_send_beacons(struct ieee80211_device *ieee) --=20 2.17.1