From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933079AbcLIDYr (ORCPT ); Thu, 8 Dec 2016 22:24:47 -0500 Received: from mail-yw0-f173.google.com ([209.85.161.173]:35937 "EHLO mail-yw0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932214AbcLIDYq (ORCPT ); Thu, 8 Dec 2016 22:24:46 -0500 MIME-Version: 1.0 In-Reply-To: References: <470947805c9f50b9649bea4f9814b2dcb6ebcc45.1481197710.git.baolin.wang@linaro.org> From: Baolin Wang Date: Fri, 9 Dec 2016 11:24:44 +0800 Message-ID: Subject: Re: [PATCH] usb: gadget: f_fs: Fix possibe deadlock To: Michal Nazarewicz Cc: Felipe Balbi , Greg KH , felixhaedicke@web.de, jilin@nvidia.com, dan.carpenter@oracle.com, lars@metafoo.de, USB , LKML , Mark Brown Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id uB93OqiH008862 Hi Michal, On 8 December 2016 at 23:18, Michal Nazarewicz wrote: > On Thu, Dec 08 2016, Baolin Wang wrote: >> When system try to close /dev/usb-ffs/adb/ep0 on one core, at the same >> time another core try to attach new UDC, which will cause deadlock as >> below scenario. Thus we should release ffs lock before issuing >> unregister_gadget_item(). >> >> [ 52.642225] c1 ====================================================== >> [ 52.642228] c1 [ INFO: possible circular locking dependency detected ] >> [ 52.642236] c1 4.4.6+ #1 Tainted: G W O >> [ 52.642241] c1 ------------------------------------------------------- >> [ 52.642245] c1 usb ffs open/2808 is trying to acquire lock: >> [ 52.642270] c0 (udc_lock){+.+.+.}, at: [] >> usb_gadget_unregister_driver+0x3c/0xc8 >> [ 52.642272] c1 but task is already holding lock: >> [ 52.642283] c0 (ffs_lock){+.+.+.}, at: [] >> ffs_data_clear+0x30/0x140 >> [ 52.642285] c1 which lock already depends on the new lock. >> [ 52.642287] c1 >> the existing dependency chain (in reverse order) is: >> [ 52.642295] c0 >> -> #1 (ffs_lock){+.+.+.}: >> [ 52.642307] c0 [] __lock_acquire+0x20f0/0x2238 >> [ 52.642314] c0 [] lock_acquire+0xe4/0x298 >> [ 52.642322] c0 [] mutex_lock_nested+0x7c/0x3cc >> [ 52.642328] c0 [] ffs_func_bind+0x504/0x6e8 >> [ 52.642334] c0 [] usb_add_function+0x84/0x184 >> [ 52.642340] c0 [] configfs_composite_bind+0x264/0x39c >> [ 52.642346] c0 [] udc_bind_to_driver+0x58/0x11c >> [ 52.642352] c0 [] usb_udc_attach_driver+0x90/0xc8 >> [ 52.642358] c0 [] gadget_dev_desc_UDC_store+0xd4/0x128 >> [ 52.642369] c0 [] configfs_write_file+0xd0/0x13c >> [ 52.642376] c0 [] vfs_write+0xb8/0x214 >> [ 52.642381] c0 [] SyS_write+0x54/0xb0 >> [ 52.642388] c0 [] el0_svc_naked+0x24/0x28 >> [ 52.642395] c0 >> -> #0 (udc_lock){+.+.+.}: >> [ 52.642401] c0 [] print_circular_bug+0x84/0x2e4 >> [ 52.642407] c0 [] __lock_acquire+0x2138/0x2238 >> [ 52.642412] c0 [] lock_acquire+0xe4/0x298 >> [ 52.642420] c0 [] mutex_lock_nested+0x7c/0x3cc >> [ 52.642427] c0 [] usb_gadget_unregister_driver+0x3c/0xc8 >> [ 52.642432] c0 [] unregister_gadget_item+0x28/0x44 >> [ 52.642439] c0 [] ffs_data_clear+0x138/0x140 >> [ 52.642444] c0 [] ffs_data_reset+0x20/0x6c >> [ 52.642450] c0 [] ffs_data_closed+0xac/0x12c >> [ 52.642454] c0 [] ffs_ep0_release+0x20/0x2c >> [ 52.642460] c0 [] __fput+0xb0/0x1f4 >> [ 52.642466] c0 [] ____fput+0x20/0x2c >> [ 52.642473] c0 [] task_work_run+0xb4/0xe8 >> [ 52.642482] c0 [] do_exit+0x360/0xb9c >> [ 52.642487] c0 [] do_group_exit+0x4c/0xb0 >> [ 52.642494] c0 [] get_signal+0x380/0x89c >> [ 52.642501] c0 [] do_signal+0x154/0x518 >> [ 52.642507] c0 [] do_notify_resume+0x70/0x78 >> [ 52.642512] c0 [] work_pending+0x1c/0x20 >> [ 52.642514] c1 >> other info that might help us debug this: >> [ 52.642517] c1 Possible unsafe locking scenario: >> [ 52.642518] c1 CPU0 CPU1 >> [ 52.642520] c1 ---- ---- >> [ 52.642525] c0 lock(ffs_lock); >> [ 52.642529] c0 lock(udc_lock); >> [ 52.642533] c0 lock(ffs_lock); >> [ 52.642537] c0 lock(udc_lock); >> [ 52.642539] c1 >> *** DEADLOCK *** >> [ 52.642543] c1 1 lock held by usb ffs open/2808: >> [ 52.642555] c0 #0: (ffs_lock){+.+.+.}, at: [] >> ffs_data_clear+0x30/0x140 >> [ 52.642557] c1 stack backtrace: >> [ 52.642563] c1 CPU: 1 PID: 2808 Comm: usb ffs open Tainted: G >> [ 52.642565] c1 Hardware name: Spreadtrum SP9860g Board (DT) >> [ 52.642568] c1 Call trace: >> [ 52.642573] c1 [] dump_backtrace+0x0/0x170 >> [ 52.642577] c1 [] show_stack+0x20/0x28 >> [ 52.642583] c1 [] dump_stack+0xa8/0xe0 >> [ 52.642587] c1 [] print_circular_bug+0x1fc/0x2e4 >> [ 52.642591] c1 [] __lock_acquire+0x2138/0x2238 >> [ 52.642595] c1 [] lock_acquire+0xe4/0x298 >> [ 52.642599] c1 [] mutex_lock_nested+0x7c/0x3cc >> [ 52.642604] c1 [] usb_gadget_unregister_driver+0x3c/0xc8 >> [ 52.642608] c1 [] unregister_gadget_item+0x28/0x44 >> [ 52.642613] c1 [] ffs_data_clear+0x138/0x140 >> [ 52.642618] c1 [] ffs_data_reset+0x20/0x6c >> [ 52.642621] c1 [] ffs_data_closed+0xac/0x12c >> [ 52.642625] c1 [] ffs_ep0_release+0x20/0x2c >> [ 52.642629] c1 [] __fput+0xb0/0x1f4 >> [ 52.642633] c1 [] ____fput+0x20/0x2c >> [ 52.642636] c1 [] task_work_run+0xb4/0xe8 >> [ 52.642640] c1 [] do_exit+0x360/0xb9c >> [ 52.642644] c1 [] do_group_exit+0x4c/0xb0 >> [ 52.642647] c1 [] get_signal+0x380/0x89c >> [ 52.642651] c1 [] do_signal+0x154/0x518 >> [ 52.642656] c1 [] do_notify_resume+0x70/0x78 >> [ 52.642659] c1 [] work_pending+0x1c/0x20 >> >> Signed-off-by: Baolin Wang > > Acked-by: Michal Nazarewicz Thanks for your ACK. > >> --- >> drivers/usb/gadget/function/f_fs.c | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c >> index 0780d83..93de3b9 100644 >> --- a/drivers/usb/gadget/function/f_fs.c >> +++ b/drivers/usb/gadget/function/f_fs.c >> @@ -3666,6 +3666,7 @@ static void ffs_closed(struct ffs_data *ffs) >> { >> struct ffs_dev *ffs_obj; >> struct f_fs_opts *opts; >> + struct config_item *ci; >> >> ENTER(); >> ffs_dev_lock(); >> @@ -3689,8 +3690,11 @@ static void ffs_closed(struct ffs_data *ffs) >> || !atomic_read(&opts->func_inst.group.cg_item.ci_kref.refcount)) >> goto done; >> >> - unregister_gadget_item(ffs_obj->opts-> >> - func_inst.group.cg_item.ci_parent->ci_parent); >> + ci = opts->func_inst.group.cg_item.ci_parent->ci_parent; >> + ffs_dev_unlock(); >> + >> + unregister_gadget_item(ci); >> + return; >> done: >> ffs_dev_unlock(); >> } >> -- >> 1.7.9.5 >> > > -- > Best regards > ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ > «If at first you don’t succeed, give up skydiving» -- Baolin.wang Best Regards