From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mga09.intel.com ([134.134.136.24]:35479 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753424Ab0G1OfS (ORCPT ); Wed, 28 Jul 2010 10:35:18 -0400 Subject: Re: [RFC] iwlwifi: fix scan abort From: "Guy, Wey-Yi" To: Stanislaw Gruszka Cc: "Chatre, Reinette" , "John W. Linville" , "linux-wireless@vger.kernel.org" In-Reply-To: <20100728154509.77e8e85b@dhcp-lab-109.englab.brq.redhat.com> References: <20100728154509.77e8e85b@dhcp-lab-109.englab.brq.redhat.com> Content-Type: text/plain Date: Wed, 28 Jul 2010 07:34:42 -0700 Message-Id: <1280327682.26765.6.camel@wwguy-ubuntu> Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi Gruszka, On Wed, 2010-07-28 at 06:45 -0700, Stanislaw Gruszka wrote: > We can not call cancel_delayed_work_sync(&priv->scan_check) with > priv->mutex locked because workqueue function iwl_bg_scan_check() > take that lock internally. > > We do not need to synchronize when canceling priv->scan_check work. > We can avoid races (sending double abort command or send no > command at all) using STATUS_SCAN_ABORT bit. Moreover > current iwl_bg_scan_check() code seems to be broken, as > we should not send abort commands when currently aborting. > > I did not test patch yet, just want to know if it is theoretically > correct. Except obvious circular priv->mutex locking fix, maybe it > can help with warning in ieee80211_scan_completed, which is still > reported by the users from time to time. > > diff --git a/drivers/net/wireless/iwlwifi/iwl-scan.c b/drivers/net/wireless/iwlwifi/iwl-scan.c > index 2a7c399..b0c6b04 100644 > --- a/drivers/net/wireless/iwlwifi/iwl-scan.c > +++ b/drivers/net/wireless/iwlwifi/iwl-scan.c > @@ -429,11 +429,10 @@ void iwl_bg_scan_check(struct work_struct *data) > return; > > mutex_lock(&priv->mutex); > - if (test_bit(STATUS_SCANNING, &priv->status) || > - test_bit(STATUS_SCAN_ABORTING, &priv->status)) { > - IWL_DEBUG_SCAN(priv, "Scan completion watchdog resetting " > - "adapter (%dms)\n", > - jiffies_to_msecs(IWL_SCAN_CHECK_WATCHDOG)); > + if (test_bit(STATUS_SCANNING, &priv->status) && > + !test_bit(STATUS_SCAN_ABORTING, &priv->status)) { > + IWL_DEBUG_SCAN(priv, "Scan completion watchdog (%dms)\n", > + jiffies_to_msecs(IWL_SCAN_CHECK_WATCHDOG)); make sense here, the code is broken, we should not abort scan if already doing it. > > if (!test_bit(STATUS_EXIT_PENDING, &priv->status)) > iwl_send_scan_abort(priv); > @@ -498,12 +497,11 @@ void iwl_bg_abort_scan(struct work_struct *work) > !test_bit(STATUS_GEO_CONFIGURED, &priv->status)) > return; > > - mutex_lock(&priv->mutex); > - > - cancel_delayed_work_sync(&priv->scan_check); > - set_bit(STATUS_SCAN_ABORTING, &priv->status); > - iwl_send_scan_abort(priv); > + cancel_delayed_work(&priv->scan_check); > > + mutex_lock(&priv->mutex); > + if (test_bit(STATUS_SCAN_ABORTING, &priv->status)) > + iwl_send_scan_abort(priv); > mutex_unlock(&priv->mutex); > } Looks right to me, thanks a lot to catch this one. Wey