From mboxrd@z Thu Jan 1 00:00:00 1970 From: "John W. Linville" Subject: [PATCH] clarify locking comment in cfg80211 Date: Thu, 26 Apr 2007 21:50:55 -0400 Message-ID: <20070427015055.GF25332@tuxdriver.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Johannes Berg , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org Return-path: Content-Disposition: inline Sender: linux-wireless-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org From: Johannes Berg This patch clarifies the comment about locking in wiphy_unregister. Signed-off-by: Johannes Berg Signed-off-by: John W. Linville --- I applied this after the "fix locking in wiphy_new" patch, but I don't think the order really matters. net/wireless/core.c | 19 +++++++++++++++---- 1 files changed, 15 insertions(+), 4 deletions(-) diff --git a/net/wireless/core.c b/net/wireless/core.c index 24a21ad..7eabd55 100644 --- a/net/wireless/core.c +++ b/net/wireless/core.c @@ -91,7 +91,6 @@ int wiphy_register(struct wiphy *wiphy) mutex_lock(&cfg80211_drv_mutex); - res = device_add(&drv->wiphy.dev); if (res) goto out_unlock; @@ -114,14 +113,26 @@ void wiphy_unregister(struct wiphy *wiphy) { struct cfg80211_registered_device *drv = wiphy_to_dev(wiphy); + /* protect the device list */ mutex_lock(&cfg80211_drv_mutex); - /* hold registered driver mutex during list removal as well - * to make sure no commands are in progress at the moment */ + BUG_ON(!list_empty(&drv->netdev_list)); + + /* + * Try to grab drv->mtx. If a command is still in progress, + * hopefully the driver will refuse it since it's tearing + * down the device already. We wait for this command to complete + * before unlinking the item from the list. + * Note: as codified by the BUG_ON above we cannot get here if + * a virtual interface is still associated. Hence, we can only + * get to lock contention here if userspace issues a command + * that identified the hardware by wiphy index. + */ mutex_lock(&drv->mtx); - list_del(&drv->list); + /* unlock again before freeing */ mutex_unlock(&drv->mtx); + list_del(&drv->list); device_del(&drv->wiphy.dev); debugfs_remove(drv->wiphy.debugfsdir); -- 1.5.0.6 -- John W. Linville linville-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org