Return-path: Received: from mail-pf0-f174.google.com ([209.85.192.174]:33448 "EHLO mail-pf0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933846AbdEVVCi (ORCPT ); Mon, 22 May 2017 17:02:38 -0400 Received: by mail-pf0-f174.google.com with SMTP id e193so93319615pfh.0 for ; Mon, 22 May 2017 14:02:38 -0700 (PDT) Subject: Re: 4.12-RC2 BUG: scheduling while atomic: irq/47-iwlwifi To: Johannes Berg , Sander Eikelenboom References: <1495450628.2653.14.camel@sipsolutions.net> <764a929c-ce8a-c859-a49e-2f20cb05ae44@broadcom.com> Cc: linux-wireless , netdev@vger.kernel.org From: Arend Van Spriel Message-ID: <532c257e-52a0-18c1-1afe-04d37c28e072@broadcom.com> (sfid-20170522_230252_260507_58963069) Date: Mon, 22 May 2017 23:02:34 +0200 MIME-Version: 1.0 In-Reply-To: <764a929c-ce8a-c859-a49e-2f20cb05ae44@broadcom.com> Content-Type: text/plain; charset=utf-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 22-5-2017 14:09, Arend van Spriel wrote: > On 5/22/2017 12:57 PM, Johannes Berg wrote: >> On Mon, 2017-05-22 at 12:36 +0200, Sander Eikelenboom wrote: >>> Hi, >>> >>> I encountered this splat with 4.12-RC2. >> >> Ugh, yeah, I should've seen that in the review. >> >> Arend, please take a look at this. cfg80211_sched_scan_results() cannot >> sleep, so you can't rtnl_lock() in there. Looks like you can just rely >> on RCU though? > > I see. I think you are right on RCU. Don't have the code in front of me > now, but I think the lookup has an ASSERT_RTNL. Will look into it after > my monday meeting :-p I realized I have a laptop lying around with intel 3160 wifi chip and tried to reproduce the issue. Did not run into the splat running 4.12-rc1 from wireless-drivers-next repo. I did not get the email from Sander so I don't know any details. Here is what I changed based on the info Johannes provided. Can you please check if this get rid of the splat and let me know. Regards, Arend --- diff --git a/net/wireless/scan.c b/net/wireless/scan.c index 14d5f0c..04833bb 100644 --- a/net/wireless/scan.c +++ b/net/wireless/scan.c @@ -322,9 +322,7 @@ static void cfg80211_del_sched_scan_req(struct cfg80211_regi { struct cfg80211_sched_scan_request *pos; - ASSERT_RTNL(); - - list_for_each_entry(pos, &rdev->sched_scan_req_list, list) { + list_for_each_entry_rcu(pos, &rdev->sched_scan_req_list, list) { if (pos->reqid == reqid) return pos; } @@ -398,13 +396,13 @@ void cfg80211_sched_scan_results(struct wiphy *wiphy, u64 trace_cfg80211_sched_scan_results(wiphy, reqid); /* ignore if we're not scanning */ - rtnl_lock(); + rcu_read_lock(); request = cfg80211_find_sched_scan_req(rdev, reqid); if (request) { request->report_results = true; queue_work(cfg80211_wq, &rdev->sched_scan_res_wk); } - rtnl_unlock(); + rcu_read_unlock(); } EXPORT_SYMBOL(cfg80211_sched_scan_results);