From f3a511912a7b56768101244a632c95d2841714d3 Mon Sep 17 00:00:00 2001 From: Baolin Wang Date: Thu, 8 Dec 2016 19:55:22 +0800 Subject: [PATCH] usb: gadget: f_fs: Fix possibe deadlock 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 Bug: 62572621 Change-Id: I78adea011c3a87dfeb5c15750b7737975fda1742 Acked-by: Michal Nazarewicz Signed-off-by: Baolin Wang Signed-off-by: Felipe Balbi (cherry picked from commit b3ce3ce02d146841af012d08506b4071db8ffde3) Signed-off-by: Jerry Zhang --- 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 89081b8..8a788d6 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -3688,6 +3688,7 @@ 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(); @@ -3711,8 +3712,11 @@ 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(); } -- 2.7.4