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authorChuansheng Liu <chuansheng.liu@intel.com>2013-12-18 13:30:11 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-18 16:58:28 -0800
commitbe7065725590dd8fbf5d6a614bcfaec4a860b998 (patch)
tree0b174c4c46637a464980c487abd63d1d45e9a658 /drivers/tty/n_gsm.c
parent8be3da65d9222e1e63b7f9d001e872947588946f (diff)
TTY/n_gsm: Removing the wrong tty_unlock/lock() in gsm_dlci_release()
Commit 4d9b109060f690f5c835(tty: Prevent deadlock in n_gsm driver) tried to close all the virtual ports synchronously before closing the phycial ports, so the tty_vhangup() is used. But the tty_unlock/lock() is wrong: tty_release tty_ldisc_release tty_lock_pair(tty, o_tty) < == Here the tty is for physical port tty_ldisc_kill gsmld_close gsm_cleanup_mux gsm_dlci_release tty = tty_port_tty_get(&dlci->port) < == Here the tty(s) are for virtual port They are different ttys, so before tty_vhangup(virtual tty), do not need to call the tty_unlock(virtual tty) at all which causes unbalanced unlock warning. When enabling mutex debugging option, we will hit the below warning also: [ 99.276903] ===================================== [ 99.282172] [ BUG: bad unlock balance detected! ] [ 99.287442] 3.10.20-261976-gaec5ba0 #44 Tainted: G O [ 99.293972] ------------------------------------- [ 99.299240] mmgr/152 is trying to release lock (&tty->legacy_mutex) at: [ 99.306693] [<c1b2dcad>] mutex_unlock+0xd/0x10 [ 99.311669] but there are no more locks to release! [ 99.317131] [ 99.317131] other info that might help us debug this: [ 99.324440] 3 locks held by mmgr/152: [ 99.328542] #0: (&tty->legacy_mutex/1){......}, at: [<c1b30ab0>] tty_lock_nested+0x40/0x90 [ 99.338116] #1: (&tty->ldisc_mutex){......}, at: [<c15dbd02>] tty_ldisc_kill+0x22/0xd0 [ 99.347284] #2: (&gsm->mutex){......}, at: [<c15e3d83>] gsm_cleanup_mux+0x73/0x170 [ 99.356060] [ 99.356060] stack backtrace: [ 99.360932] CPU: 0 PID: 152 Comm: mmgr Tainted: G O 3.10.20-261976-gaec5ba0 #44 [ 99.370086] ef4a4de0 ef4a4de0 ef4c1d98 c1b27b91 ef4c1db8 c1292655 c1dd10f5 c1b2dcad [ 99.378921] c1b2dcad ef4a4de0 ef4a528c ffffffff ef4c1dfc c12930dd 00000246 00000000 [ 99.387754] 00000000 00000000 c15e1926 00000000 00000001 ddfa7530 00000003 c1b2dcad [ 99.396588] Call Trace: [ 99.399326] [<c1b27b91>] dump_stack+0x16/0x18 [ 99.404307] [<c1292655>] print_unlock_imbalance_bug+0xe5/0xf0 [ 99.410840] [<c1b2dcad>] ? mutex_unlock+0xd/0x10 [ 99.416110] [<c1b2dcad>] ? mutex_unlock+0xd/0x10 [ 99.421382] [<c12930dd>] lock_release_non_nested+0x1cd/0x210 [ 99.427818] [<c15e1926>] ? gsm_destroy_network+0x36/0x130 [ 99.433964] [<c1b2dcad>] ? mutex_unlock+0xd/0x10 [ 99.439235] [<c12931a2>] lock_release+0x82/0x1c0 [ 99.444505] [<c1b2dcad>] ? mutex_unlock+0xd/0x10 [ 99.449776] [<c1b2dcad>] ? mutex_unlock+0xd/0x10 [ 99.455047] [<c1b2dc2f>] __mutex_unlock_slowpath+0x5f/0xd0 [ 99.461288] [<c1b2dcad>] mutex_unlock+0xd/0x10 [ 99.466365] [<c1b30bb1>] tty_unlock+0x21/0x50 [ 99.471345] [<c15e3dd1>] gsm_cleanup_mux+0xc1/0x170 [ 99.476906] [<c15e44d2>] gsmld_close+0x52/0x90 [ 99.481983] [<c15db905>] tty_ldisc_close.isra.1+0x35/0x50 [ 99.488127] [<c15dbd0c>] tty_ldisc_kill+0x2c/0xd0 [ 99.493494] [<c15dc7af>] tty_ldisc_release+0x2f/0x50 [ 99.499152] [<c15d572c>] tty_release+0x37c/0x4b0 [ 99.504424] [<c1b2dcad>] ? mutex_unlock+0xd/0x10 [ 99.509695] [<c1b2dcad>] ? mutex_unlock+0xd/0x10 [ 99.514967] [<c1372f6e>] ? eventpoll_release_file+0x7e/0x90 [ 99.521307] [<c1335849>] __fput+0xd9/0x200 [ 99.525996] [<c133597d>] ____fput+0xd/0x10 [ 99.530685] [<c125c731>] task_work_run+0x81/0xb0 [ 99.535957] [<c12019e9>] do_notify_resume+0x49/0x70 [ 99.541520] [<c1b30dc4>] work_notifysig+0x29/0x31 [ 99.546897] ------------[ cut here ]------------ So here we can call tty_vhangup() directly which is for virtual port. Reviewed-by: Chao Bi <chao.bi@intel.com> Signed-off-by: Liu, Chuansheng <chuansheng.liu@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/n_gsm.c')
-rw-r--r--drivers/tty/n_gsm.c5
1 files changed, 1 insertions, 4 deletions
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index b94737b54e3e..f34461c5f14e 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1705,11 +1705,8 @@ static void gsm_dlci_release(struct gsm_dlci *dlci)
gsm_destroy_network(dlci);
mutex_unlock(&dlci->mutex);
- /* tty_vhangup needs the tty_lock, so unlock and
- relock after doing the hangup. */
- tty_unlock(tty);
tty_vhangup(tty);
- tty_lock(tty);
+
tty_port_tty_set(&dlci->port, NULL);
tty_kref_put(tty);
}