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 68A471FB4 for ; Fri, 3 Feb 2023 10:18:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5016C433D2; Fri, 3 Feb 2023 10:18:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1675419521; bh=D4M29BTteyS3xWJOfQL/c5/hQpFbOp7cxr30QXQYRbI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=a6WtSqht9ptjyuhmCx7a7lscLw/T+IZ+nftrHBVb8Oi+7l4fowdtfZP5+bhAwhHBt SM5I5KWKcNn86nNkA9ZG3KgnVX1Ssr/3DpfrwfK3AzZAmd5G7HC1TtE29dlY/1PZA0 X63grBg939siGAYEjPudQRcsJbTXCR5HQixipexY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yang Yingliang , Sasha Levin Subject: [PATCH 4.19 30/80] w1: fix deadloop in __w1_remove_master_device() Date: Fri, 3 Feb 2023 11:12:24 +0100 Message-Id: <20230203101016.464087441@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230203101015.263854890@linuxfoundation.org> References: <20230203101015.263854890@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Yang Yingliang [ Upstream commit 25d5648802f12ae486076ceca5d7ddf1fef792b2 ] I got a deadloop report while doing device(ds2482) add/remove test: [ 162.241881] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1. [ 163.272251] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1. [ 164.296157] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1. ... __w1_remove_master_device() can't return, because the dev->refcnt is not zero. w1_add_master_device() | w1_alloc_dev() | atomic_set(&dev->refcnt, 2) | kthread_run() | |__w1_remove_master_device() | kthread_stop() // KTHREAD_SHOULD_STOP is set, | // threadfn(w1_process) won't be | // called. | kthread() | | // refcnt will never be 0, it's deadloop. | while (atomic_read(&dev->refcnt)) {...} After calling w1_add_master_device(), w1_process() is not really invoked, before w1_process() starting, if kthread_stop() is called in __w1_remove_master_device(), w1_process() will never be called, the refcnt can not be decreased, then it causes deadloop in remove function because of non-zero refcnt. We need to make sure w1_process() is really started, so move the set refcnt into w1_process() to fix this problem. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Yang Yingliang Link: https://lore.kernel.org/r/20221205080434.3149205-1-yangyingliang@huawei.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/w1/w1.c | 2 ++ drivers/w1/w1_int.c | 5 ++--- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c index 890c038c25f8..c1d0e723fabc 100644 --- a/drivers/w1/w1.c +++ b/drivers/w1/w1.c @@ -1140,6 +1140,8 @@ int w1_process(void *data) /* remainder if it woke up early */ unsigned long jremain = 0; + atomic_inc(&dev->refcnt); + for (;;) { if (!jremain && dev->search_count) { diff --git a/drivers/w1/w1_int.c b/drivers/w1/w1_int.c index 1c776178f598..eb851eb44300 100644 --- a/drivers/w1/w1_int.c +++ b/drivers/w1/w1_int.c @@ -60,10 +60,9 @@ static struct w1_master *w1_alloc_dev(u32 id, int slave_count, int slave_ttl, dev->search_count = w1_search_count; dev->enable_pullup = w1_enable_pullup; - /* 1 for w1_process to decrement - * 1 for __w1_remove_master_device to decrement + /* For __w1_remove_master_device to decrement */ - atomic_set(&dev->refcnt, 2); + atomic_set(&dev->refcnt, 1); INIT_LIST_HEAD(&dev->slist); INIT_LIST_HEAD(&dev->async_list); -- 2.39.0