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Daniel Starke 7962a4b900 tty: n_gsm: fix deadlock and link starvation in outgoing data path [ Upstream commit `0af021678d` ] The current implementation queues up new control and user packets as needed and processes this queue down to the ldisc in the same code path. That means that the upper and the lower layer are hard coupled in the code. Due to this deadlocks can happen as seen below while transmitting data, especially during ldisc congestion. Furthermore, the data channels starve the control channel on high transmission load on the ldisc. Introduce an additional control channel data queue to prevent timeouts and link hangups during ldisc congestion. This is being processed before the user channel data queue in gsm_data_kick(), i.e. with the highest priority. Put the queue to ldisc data path into a workqueue and trigger it whenever new data has been put into the transmission queue. Change gsm_dlci_data_sweep() accordingly to fill up the transmission queue until TX_THRESH_HI. This solves the locking issue, keeps latency low and provides good performance on high data load. Note that now all packets from a DLCI are removed from the internal queue if the associated DLCI was closed. This ensures that no data is sent by the introduced write task to an already closed DLCI. BUG: spinlock recursion on CPU#0, test_v24_loop/124 lock: serial8250_ports+0x3a8/0x7500, .magic: dead4ead, .owner: test_v24_loop/124, .owner_cpu: 0 CPU: 0 PID: 124 Comm: test_v24_loop Tainted: G O 5.18.0-rc2 #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Call Trace: <IRQ> dump_stack_lvl+0x34/0x44 do_raw_spin_lock+0x76/0xa0 _raw_spin_lock_irqsave+0x72/0x80 uart_write_room+0x3b/0xc0 gsm_data_kick+0x14b/0x240 [n_gsm] gsmld_write_wakeup+0x35/0x70 [n_gsm] tty_wakeup+0x53/0x60 tty_port_default_wakeup+0x1b/0x30 serial8250_tx_chars+0x12f/0x220 serial8250_handle_irq.part.0+0xfe/0x150 serial8250_default_handle_irq+0x48/0x80 serial8250_interrupt+0x56/0xa0 __handle_irq_event_percpu+0x78/0x1f0 handle_irq_event+0x34/0x70 handle_fasteoi_irq+0x90/0x1e0 __common_interrupt+0x69/0x100 common_interrupt+0x48/0xc0 asm_common_interrupt+0x1e/0x40 RIP: 0010:__do_softirq+0x83/0x34e Code: 2a 0a ff 0f b7 ed c7 44 24 10 0a 00 00 00 48 c7 c7 51 2a 64 82 e8 2d e2 d5 ff 65 66 c7 05 83 af 1e 7e 00 00 fb b8 ff ff ff ff <49> c7 c2 40 61 80 82 0f bc c5 41 89 c4 41 83 c4 01 0f 84 e6 00 00 RSP: 0018:ffffc90000003f98 EFLAGS: 00000286 RAX: 00000000ffffffff RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff82642a51 RDI: ffffffff825bb5e7 RBP: 0000000000000200 R08: 00000008de3271a8 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000030 R14: 0000000000000000 R15: 0000000000000000 ? __do_softirq+0x73/0x34e irq_exit_rcu+0xb5/0x100 common_interrupt+0xa4/0xc0 </IRQ> <TASK> asm_common_interrupt+0x1e/0x40 RIP: 0010:_raw_spin_unlock_irqrestore+0x2e/0x50 Code: 00 55 48 89 fd 48 83 c7 18 53 48 89 f3 48 8b 74 24 10 e8 85 28 36 ff 48 89 ef e8 cd 58 36 ff 80 e7 02 74 01 fb bf 01 00 00 00 <e8> 3d 97 33 ff 65 8b 05 96 23 2b 7e 85 c0 74 03 5b 5d c3 0f 1f 44 RSP: 0018:ffffc9000020fd08 EFLAGS: 00000202 RAX: 0000000000000000 RBX: 0000000000000246 RCX: 0000000000000000 RDX: 0000000000000004 RSI: ffffffff8257fd74 RDI: 0000000000000001 RBP: ffff8880057de3a0 R08: 00000008de233000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000100 R14: 0000000000000202 R15: ffff8880057df0b8 ? _raw_spin_unlock_irqrestore+0x23/0x50 gsmtty_write+0x65/0x80 [n_gsm] n_tty_write+0x33f/0x530 ? swake_up_all+0xe0/0xe0 file_tty_write.constprop.0+0x1b1/0x320 ? n_tty_flush_buffer+0xb0/0xb0 new_sync_write+0x10c/0x190 vfs_write+0x282/0x310 ksys_write+0x68/0xe0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f3e5e35c15c Code: 8b 7c 24 08 89 c5 e8 c5 ff ff ff 89 ef 89 44 24 08 e8 58 bc 02 00 8b 44 24 08 48 83 c4 10 5d c3 48 63 ff b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 76 10 48 8b 15 fd fc 05 00 f7 d8 64 89 02 48 83 RSP: 002b:00007ffcee77cd18 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007ffcee77cd70 RCX: 00007f3e5e35c15c RDX: 0000000000000100 RSI: 00007ffcee77cd90 RDI: 0000000000000003 RBP: 0000000000000100 R08: 0000000000000000 R09: 7efefefefefefeff R10: 00007f3e5e3bddeb R11: 0000000000000246 R12: 00007ffcee77ce8f R13: 0000000000000001 R14: 000056214404e010 R15: 00007ffcee77cd90 </TASK> Fixes: `e1eaea46bb` ("tty: n_gsm line discipline") Signed-off-by: Daniel Starke <daniel.starke@siemens.com> Link: https://lore.kernel.org/r/20220701122332.2039-1-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		History 2022-08-17 15:15:49 +02:00
arch	powerpc/perf: Optimize clearing the pending PMI and remove WARN_ON for PMI check in power_pmu_disable	2022-08-17 15:15:47 +02:00
block	block: ensure iov_iter advances for added pages	2022-08-17 15:15:43 +02:00
certs	certs: make system keyring depend on x509 parser	2022-07-24 12:53:55 -07:00
crypto	crypto: s390 - do not depend on CRYPTO_HW for SIMD implementations	2022-07-06 20:04:06 -07:00
Documentation	dt-bindings: mmc: sdhci-msm: Fix issues in yaml bindings	2022-08-17 15:15:30 +02:00
drivers	tty: n_gsm: fix deadlock and link starvation in outgoing data path	2022-08-17 15:15:49 +02:00
fs	jbd2: fix assertion 'jh->b_frozen_data == NULL' failure when journal aborted	2022-08-17 15:15:43 +02:00
include	vfio: Split migration ops from main device ops	2022-08-17 15:15:48 +02:00
init	stack: Declare {randomize_,}kstack_offset to fix Sparse warnings	2022-08-17 15:14:14 +02:00
io_uring	io_uring: Don't require reinitable percpu_ref	2022-08-17 15:14:20 +02:00
ipc	ipc: Free mq_sysctls if ipc namespace creation failed	2022-06-22 17:47:41 -05:00
kernel	profiling: fix shift too large makes kernel panic	2022-08-17 15:15:46 +02:00
lib	selftests/livepatch: better synchronize test_klp_callbacks_busy	2022-08-17 15:15:46 +02:00
LICENSES	LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers	2021-12-16 14:33:10 +01:00
mm	mm/mmap.c: fix missing call to vm_unacct_memory in mmap_region	2022-08-17 15:15:40 +02:00
net	dccp: put dccp_qpolicy_full() and dccp_qpolicy_push() in the same lock	2022-08-17 15:14:59 +02:00
samples	sample: bpf: xdp_router_ipv4: Allow the kernel to send arp requests	2022-08-17 15:14:25 +02:00
scripts	scripts/gdb: fix 'lx-dmesg' on 32 bits arch	2022-08-17 15:15:36 +02:00
security	selinux: Add boundary check in put_entry()	2022-08-17 15:14:06 +02:00
sound	ASoC: codecs: wsa881x: handle timeouts in resume path	2022-08-17 15:15:48 +02:00
tools	selftests/powerpc: Skip energy_scale_info test on older firmware	2022-08-17 15:15:47 +02:00
usr	Not a lot of material this cycle. Many singleton patches against various	2022-05-27 11:22:03 -07:00
virt	KVM: Don't set Accessed/Dirty bits for ZERO_PAGE	2022-08-17 15:15:21 +02:00
.clang-format	clang-format: Fix space after for_each macros	2022-05-20 19:27:16 +02:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	kbuild: split the second line of .mod into .usyms	2022-05-08 03:16:59 +09:00
.mailmap	ARM: SoC fixes for 5.19, part 4	2022-07-27 09:43:07 -07:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: mark ARM/PALM TREO SUPPORT orphan	2022-07-07 15:17:00 +02:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	io_uring: move to separate directory	2022-08-17 15:14:20 +02:00
Makefile	io_uring: move to separate directory	2022-08-17 15:14:20 +02:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.