Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753140AbcLHLzj (ORCPT ); Thu, 8 Dec 2016 06:55:39 -0500 Received: from mail-pg0-f42.google.com ([74.125.83.42]:34901 "EHLO mail-pg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752221AbcLHLzh (ORCPT ); Thu, 8 Dec 2016 06:55:37 -0500 From: Baolin Wang To: balbi@kernel.org Cc: gregkh@linuxfoundation.org, mina86@mina86.com, felixhaedicke@web.de, jilin@nvidia.com, dan.carpenter@oracle.com, lars@metafoo.de, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, broonie@kernel.org, baolin.wang@linaro.org Subject: [PATCH] usb: gadget: f_fs: Fix possibe deadlock Date: Thu, 8 Dec 2016 19:55:22 +0800 Message-Id: <470947805c9f50b9649bea4f9814b2dcb6ebcc45.1481197710.git.baolin.wang@linaro.org> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6607 Lines: 128 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 --- 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