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As the association status changes the driver needs to configure the hardware. This is done based on information in the "sta" acquired by ieee80211_find_sta(), which requires the caller to ensure that the "sta" is valid while its being used; generally by entering an rcu read section. But the operations acting on the "sta" has to communicate with the firmware and may therefor sleep, resulting in the following report: [ 31.418190] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:238 [ 31.425919] in_atomic(): 0, irqs_disabled(): 0, pid: 34, name: kworker/u8:1 [ 31.434609] CPU: 0 PID: 34 Comm: kworker/u8:1 Tainted: G W 4.12.0-rc4-next-20170607+ #993 [ 31.441002] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT) [ 31.450380] Workqueue: phy0 ieee80211_iface_work [ 31.457226] Call trace: [ 31.461830] [<ffffff8008088c58>] dump_backtrace+0x0/0x260 [ 31.464004] [<ffffff8008088f7c>] show_stack+0x14/0x20 [ 31.469557] [<ffffff8008392e70>] dump_stack+0x98/0xb8 [ 31.474592] [<ffffff80080e4330>] ___might_sleep+0xf0/0x118 [ 31.479626] [<ffffff80080e43a8>] __might_sleep+0x50/0x88 [ 31.485010] [<ffffff80088ff9a4>] mutex_lock+0x24/0x60 [ 31.490479] [<ffffff8008595c38>] wcn36xx_smd_set_link_st+0x30/0x130 [ 31.495428] [<ffffff8008591ed8>] wcn36xx_bss_info_changed+0x148/0x448 [ 31.501504] [<ffffff80088ab3c4>] ieee80211_bss_info_change_notify+0xbc/0x118 [ 31.508102] [<ffffff80088f841c>] ieee80211_assoc_success+0x664/0x7f8 [ 31.515220] [<ffffff80088e13d4>] ieee80211_rx_mgmt_assoc_resp+0x144/0x2d8 [ 31.521555] [<ffffff80088e1e20>] ieee80211_sta_rx_queued_mgmt+0x190/0x698 [ 31.528239] [<ffffff80088bc44c>] ieee80211_iface_work+0x234/0x368 [ 31.535011] [<ffffff80080d81ac>] process_one_work+0x1cc/0x340 [ 31.541086] [<ffffff80080d8368>] worker_thread+0x48/0x430 [ 31.546814] [<ffffff80080de448>] kthread+0x108/0x138 [ 31.552195] [<ffffff8008082ec0>] ret_from_fork+0x10/0x50 In order to ensure that the "sta" remains alive (and consistent) for the duration of bss_info_changed() mutual exclusion has to be ensured with sta_remove(). This is done by introducing a mutex to cover firmware configuration changes, which is made to also ensure mutual exclusion between other operations changing the state or configuration of the firmware. With this we can drop the rcu read lock. Cc: stable@vger.kernel.org Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org> Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.