kernel/linux.git/drivers/tty/tty_buffer.c, branch v4.14.263

tty: tty_buffer: Fix the softlockup issue in flush_to_ldisc

2021-11-26T10:40:38+00:00

[ Upstream commit 3968ddcf05fb4b9409cd1859feb06a5b0550a1c1 ] When running ltp testcase(ltp/testcases/kernel/pty/pty04.c) with arm64, there is a soft lockup, which look like this one: Workqueue: events_unbound flush_to_ldisc Call trace: dump_backtrace+0x0/0x1ec show_stack+0x24/0x30 dump_stack+0xd0/0x128 panic+0x15c/0x374 watchdog_timer_fn+0x2b8/0x304 __run_hrtimer+0x88/0x2c0 __hrtimer_run_queues+0xa4/0x120 hrtimer_interrupt+0xfc/0x270 arch_timer_handler_phys+0x40/0x50 handle_percpu_devid_irq+0x94/0x220 __handle_domain_irq+0x88/0xf0 gic_handle_irq+0x84/0xfc el1_irq+0xc8/0x180 slip_unesc+0x80/0x214 [slip] tty_ldisc_receive_buf+0x64/0x80 tty_port_default_receive_buf+0x50/0x90 flush_to_ldisc+0xbc/0x110 process_one_work+0x1d4/0x4b0 worker_thread+0x180/0x430 kthread+0x11c/0x120 In the testcase pty04, The first process call the write syscall to send data to the pty master. At the same time, the workqueue will do the flush_to_ldisc to pop data in a loop until there is no more data left. When the sender and workqueue running in different core, the sender sends data fastly in full time which will result in workqueue doing work in loop for a long time and occuring softlockup in flush_to_ldisc with kernel configured without preempt. So I add need_resched check and cond_resched in the flush_to_ldisc loop to avoid it. Signed-off-by: Guanghui Feng Link: https://lore.kernel.org/r/1633961304-24759-1-git-send-email-guanghuifeng@linux.alibaba.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

tty: increase the default flip buffer limit to 2*640K

2019-04-05T20:31:37+00:00

[ Upstream commit 7ab57b76ebf632bf2231ccabe26bea33868118c6 ] We increase the default limit for buffer memory allocation by a factor of 10 to 640K to prevent data loss when using fast serial interfaces. For example when using RS485 without flow-control at speeds of 1Mbit/s an upwards we've run into problems such as applications being too slow to read out this buffer (on embedded devices based on imx53 or imx6). If you want to write transmitted data to a slow SD card and thus have realtime requirements, this limit can become a problem. That shouldn't be the case and 640K buffers fix such problems for us. This value is a maximum limit for allocation only. It has no effect on systems that currently run fine. When transmission is slow enough applications and hardware can keep up and increasing this limit doesn't change anything. It only _allows_ to allocate more than 2*64K in cases we currently fail to allocate memory despite having some. Signed-off-by: Manfred Schlaegl Signed-off-by: Martin Kepplinger Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

tty: wipe buffer.

2018-12-01T08:42:59+00:00

commit c9a8e5fce009e3c601a43c49ea9dbcb25d1ffac5 upstream. After we are done with the tty buffer, zero it out. Reported-by: aszlig Tested-by: Milan Broz Tested-by: Daniel Zatovic Tested-by: aszlig Cc: Willy Tarreau Signed-off-by: Greg Kroah-Hartman

tty: fix tty_ldisc_receive_buf() documentation

2018-01-02T19:31:17+00:00

commit e7e51dcf3b8a5f65c5653a054ad57eb2492a90d0 upstream. The tty_ldisc_receive_buf() helper returns the number of bytes processed so drop the bogus "not" from the kernel doc comment. Fixes: 8d082cd300ab ("tty: Unify receive_buf() code paths") Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman

tty: fix __tty_insert_flip_char regression

2017-08-02T13:58:17+00:00

Sergey noticed a small but fatal mistake in __tty_insert_flip_char, leading to an oops in an interrupt handler when using any serial port. The problem is that I accidentally took the tty_buffer pointer before calling __tty_buffer_request_room(), which replaces the buffer. This moves the pointer lookup to the right place after allocating the new buffer space. Fixes: 979990c62848 ("tty: improve tty_insert_flip_char() fast path") Reported-by: Sergey Senozhatsky Tested-by: Sergey Senozhatsky Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman

tty: improve tty_insert_flip_char() slow path

2017-07-30T14:52:19+00:00

While working on improving the fast path of tty_insert_flip_char(), I noticed that by calling tty_buffer_request_room(), we needlessly move to the separate flag buffer mode for the tty, even when all characters use TTY_NORMAL as the flag. This changes the code to call __tty_buffer_request_room() with the correct flag, which will then allocate a regular buffer when it rounds out of space but no special flags have been used. I'm guessing that this is the behavior that Peter Hurley intended when he introduced the compacted flip buffers. Fixes: acc0f67f307f ("tty: Halve flip buffer GFP_ATOMIC memory consumption") Cc: Peter Hurley Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman

tty: improve tty_insert_flip_char() fast path

2017-07-30T14:52:19+00:00

kernelci.org reports a crazy stack usage for the VT code when CONFIG_KASAN is enabled: drivers/tty/vt/keyboard.c: In function 'kbd_keycode': drivers/tty/vt/keyboard.c:1452:1: error: the frame size of 2240 bytes is larger than 2048 bytes [-Werror=frame-larger-than=] The problem is that tty_insert_flip_char() gets inlined many times into kbd_keycode(), and also into other functions, and each copy requires 128 bytes for stack redzone to check for a possible out-of-bounds access on the 'ch' and 'flags' arguments that are passed into tty_insert_flip_string_flags as a variable-length string. This introduces a new __tty_insert_flip_char() function for the slow path, which receives the two arguments by value. This completely avoids the problem and the stack usage goes back down to around 100 bytes. Without KASAN, this is also slightly better, as we don't have to spill the arguments to the stack but can simply pass 'ch' and 'flag' in registers, saving a few bytes in .text for each call site. This should be backported to linux-4.0 or later, which first introduced the stack sanitizer in the kernel. Cc: stable@vger.kernel.org Fixes: c420f167db8c ("kasan: enable stack instrumentation") Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman

tty_port: Add port client functions

2017-02-03T09:17:02+00:00

Introduce a client (upward direction) operations struct for tty_port clients. Initially supported operations are for receiving data and write wake-up. This will allow for having clients other than an ldisc. Convert the calls to the ldisc to use the client ops as the default operations. Signed-off-by: Rob Herring Reviewed-By: Sebastian Reichel Tested-By: Sebastian Reichel Signed-off-by: Greg Kroah-Hartman

tty: constify tty_ldisc_receive_buf buffer pointer

2017-01-19T16:22:34+00:00

This is needed to work with the client operations which uses const ptrs. Really, the flags pointer could be const, too, but this would be a tree wide fix. Signed-off-by: Rob Herring Reviewed-by: Andy Shevchenko Reviewed-By: Sebastian Reichel Signed-off-by: Greg Kroah-Hartman

Fix OpenSSH pty regression on close

2016-05-01T20:22:54+00:00

OpenSSH expects the (non-blocking) read() of pty master to return EAGAIN only if it has received all of the slave-side output after it has received SIGCHLD. This used to work on pre-3.12 kernels. This fix effectively forces non-blocking read() and poll() to block for parallel i/o to complete for all ttys. It also unwinds these changes: 1) f8747d4a466ab2cafe56112c51b3379f9fdb7a12 tty: Fix pty master read() after slave closes 2) 52bce7f8d4fc633c9a9d0646eef58ba6ae9a3b73 pty, n_tty: Simplify input processing on final close 3) 1a48632ffed61352a7810ce089dc5a8bcd505a60 pty: Fix input race when closing Inspired by analysis and patch from Marc Aurele La France Reported-by: Volth Reported-by: Marc Aurele La France BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=52 BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=2492 Signed-off-by: Brian Bloniarz Reviewed-by: Peter Hurley Cc: stable Signed-off-by: Greg Kroah-Hartman