Re: Query: Regarding crash in n_tty_receive_buf_common during boot

[Greg KH]

On Tue, Dec 26, 2017 at 05:58:55PM +0530, Kohli, Gaurav wrote:
> Hi ,
> We have seen lot of crashes in 4.9 during boot in n_tty_receive_buf_common,
> when tty->disc_data
> becomes NULL, Below is the call stack for same
> 29.710969] PC is at n_tty_receive_buf_common+0x68/0xa3c
> [   29.716425] LR is at n_tty_receive_buf_common+0x58/0xa3c
> [   29.721882] pc : [<ffffff80085a7450>] lr : [<ffffff80085a7440>] pstate:
> 80c00145
> [   29.721885] sp : ffffffc0a2b83c30
> [   29.721889] x29: ffffffc0a2b83c30 x28: ffffffc093c00080
> [   29.723875] x27: ffffff8009b7c0e8 x26: ffffff8009145000
> [   29.729218] x25: ffffff8009cdd748 x24: ffffffc0ee040028
> [   29.729225] x23: ffffffc093c7f280 x22: 0000000000000000
> [   29.729231] x21: ffffffc0e3a5cf62 x20: 0000000000000032
> [   29.729238] x19: 0000000000000000 x18: 0000000000000000
> [   29.729245] x17: 0000000000000000 x16: 0000000000000000
> [   29.729252] x15: 0000000000000000 x14: ffffffc0fb3de310
> [   29.729259] x13: ffffffc0fb3de308 x12: 0000000000000000
> [   29.729265] x11: ffffffc0f641aa80 x10: 0000000000000b10
> [   29.729272] x9 : ffffffc0a2b83ce0 x8 : ffffffc0a2b91cf0
> [   29.729279] x7 : 7aa17304d29fd900 x6 : ffffff8009bef778
> [   29.729285] x5 : ffffff80085a7e24 x4 : 0000000000000001
> [   29.729292] x3 : 0000000000000032 x2 : 0000000000000000
> [   29.729581] x1 : 0000000000000000 x0 : 0000000000002260
> [   29.732927]
> [   29.732927] PC: 0xffffff80085a7410:
> [   29.738025] 7410  9104e381 aa0103f6 aa0203f3 2a0303f4 b9009ba4 f90033a1
> d503201f aa1603e0
> [   29.740517] 7430  b9009fbf f941af96 d0005cfa 942acb7f 91174340 f90047a0
> d2844c00 8b160000
> [   29.743892] 7450  c8dffc03 f94002c2 52820000 b941eb81 4b020000 0b030000
> 361800e1 528aaac1
> [   29.749003] 7470  11000800 72aaaaa1 9b217c01 d360fc21 4b807c20 51000400
> 52800001 6b1f001f
> [   29.753967]
> [   29.753967] LR: 0xffffff80085a7400:
> [   29.759068] 7400  a90573fb aa0003fc aa0103f5 aa1e03e0 9104e381 aa0103f6
> aa0203f3 2a0303f4
> [   29.760110] 7420  b9009ba4 f90033a1 d503201f aa1603e0 b9009fbf f941af96
> d0005cfa 942acb7f
> [   29.766051] 7440  91174340 f90047a0 d2844c00 8b160000 c8dffc03 f94002c2
> 52820000 b941eb81
> [   29.773012] 7460  4b020000 0b030000 361800e1 528aaac1 11000800 72aaaaa1
> 9b217c01 d360fc21
> [   29.779088]
> [   29.779088] SP: 0xffffffc0a2b83bf0:
> [   29.779092] 3bf0  085a7440 ffffff80 a2b83c30 ffffffc0 085a7450 ffffff80
> 80c00145 00000000
> [   29.779113] 3c10  a2b83c30 ffffffc0 085a7440 ffffff80 ffffffff ffffffff
> 09059d28 ffffff80
> [   29.779134] 3c30  a2b83cd0 ffffffc0 085a7e60 ffffff80 93c00080 ffffffc0
> e3a5ce80 ffffffc0
> [   29.779155] 3c50  ee040008 ffffffc0 ee040000 ffffffc0 93c7f280 ffffffc0
> ee040028 ffffffc0
> [   29.779177] Process kworker/u16:10 (pid: 1216, stack limit =
> 0xffffffc0a2b80000)
> [   29.779181] Call trace:
> [   29.779186] Exception stack(0xffffffc0a2b83a40 to 0xffffffc0a2b83b70)
> [   29.779191] 3a40: 0000000000000000 0000008000000000 ffffffc0a2b83c30
> ffffff80085a7450
> [   29.779195] 3a60: 0000000080c00145 ffffffc0a2b83ba0 ffffffc0a2b91180
> ffffffc0a2b91180
> [   29.787281] 3a80: ffffff8009cdd6d0 ffffff80080f6ff8 ffffffc0a2b83aa0
> ffffff8008088e88
> [   29.787285] 3aa0: ffffffc0a2b83ab0 ffffff8008155758 ffffffc0a2b83ae0
> ffffff8008183760
> [   29.787289] 3ac0: ffffffc0a2b91180 ffffffc0f66781b0 ffffffc0f41be520
> ffffffc0f41be540
> [   29.787293] 3ae0: ffffffc0a2b83b10 ffffff800818cd50 ffffffc0f41be480
> 7aa17304d29fd900
> [   29.795323] 3b00: 0000000000002260 0000000000000000 0000000000000000
> 0000000000000032
> [   29.795327] 3b20: 0000000000000001 ffffff80085a7e24 ffffff8009bef778
> 7aa17304d29fd900
> [   29.803361] 3b40: ffffffc0a2b91cf0 ffffffc0a2b83ce0 0000000000000b10
> ffffffc0f641aa80
> [   29.803364] 3b60: 0000000000000000 ffffffc0fb3de308
> [   29.808376] [<ffffff80085a7450>] n_tty_receive_buf_common+0x68/0xa3c
> [   29.814893] [<ffffff80085a7e60>] n_tty_receive_buf2+0x3c/0x48
> [   29.820791] [<ffffff80085ab1f8>] flush_to_ldisc+0xe4/0x124
> [   29.820798] [<ffffff80080c7f78>] process_one_work+0x184/0x480
> [   29.826696] [<ffffff80080c83b4>] worker_thread+0x140/0x4b4
> [   29.826701] [<ffffff80080cf2cc>] kthread+0xf4/0x108
> I have seen some earlier patch which is fixing the same
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=71472fa9c52b1da27663c275d416d8654b905f05
> 
> but it is reverted finally in below commit:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=71472fa9c52b1da27663c275d416d8654b905f05.
> Do we have any fix available for above bug, please revert me for any further
> information.

Nope, no new information, see the archives for details :)

But have you tried 4.14?  It might be better in this area...

good luck!

greg k-h