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 <guanghuifeng@linux.alibaba.com>
Link: https://lore.kernel.org/r/1633961304-24759-1-git-send-email-guanghuifeng@linux.alibaba.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
With W=1, the kernel-doc checker complains quite a lot in the tty layer.
Over the time, many documented parameters were renamed, removed or
switched from tty to tty_port and similar. Some were mistyped in the doc
too.
So fix all these in the tty core. (But do not add the missing ones which
the checker complains about too. Not now.) The rest in the tty layer
will follow in the next patches.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200818085655.12071-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 <manfred.schlaegl@ginzinger.com>
Signed-off-by: Martin Kepplinger <martin.kepplinger@ginzinger.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When we leak some tty buffer, warn about that. For that we need to
account the memory used also in the tty_buffer_free_all function. On
other locations, the accounting is handled correctly.
Note that we do not account the free list, as that was accounted in
tty_buffer_free before put on the free list.
I have been using this patch for ages, so let's see if anybody else
encounters any issues.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The tty_ldisc_receive_buf() helper returns the number of bytes
processed so drop the bogus "not" from the kernel doc comment.
Fixes: 8d082cd300 ("tty: Unify receive_buf() code paths")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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: 979990c628 ("tty: improve tty_insert_flip_char() fast path")
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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: acc0f67f30 ("tty: Halve flip buffer GFP_ATOMIC memory consumption")
Cc: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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: c420f167db ("kasan: enable stack instrumentation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 <robh@kernel.org>
Reviewed-By: Sebastian Reichel <sre@kernel.org>
Tested-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 <robh@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Instead of two distinct code branches for receive_buf() handling,
use tty_ldisc_receive_buf() as the single code path.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The commonly accepted wisdom that scheduling work on the same cpu
that handled interrupt i/o benefits from cache-locality is only
true if the cpu is idle (since bound kworkers are often the highest
vruntime and thus the lowest priority).
Measurements of scheduling via the unbound queue show lowered
worst-case latency responses of up to 5x over bound workqueue, without
increase in average latency or throughput.
pty i/o test measurements show >3x (!) reduced total running time; tests
previously taking ~8s now complete in <2.5s.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Introduce API functions to restart and cancel tty buffer work, rather
than manipulate buffer work directly.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
