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Oliver Neukum df3aa13c7b Revert "cdc-acm: implement put_char() and flush_chars()" This reverts commit `a81cf9799a`. The patch causes a regression, which I cannot find the reason for. So let's revert for now, as a revert hurts only performance. Original report: I was trying to resolve the problem with Oliver but we don't get any conclusion for 5 months, so I am now sending this to mail list and cdc_acm authors. I am using simple request-response protocol to obtain the boiller parameters in constant intervals. A simple one transaction is: 1. opening the /dev/ttyACM0 2. sending the following 10-bytes request to the device: unsigned char req[] = {0x02, 0xfe, 0x01, 0x05, 0x08, 0x02, 0x01, 0x69, 0xab, 0x03}; 3. reading response (frame of 74 bytes length). 4. closing the descriptor I am doing this transaction with 5 seconds intervals. Before the bad commit everything was working correctly: I've got a requests and a responses in a timely manner. After the bad commit more time I am using the kernel module, more problems I have. The graph [2] is showing the problem. As you can see after module load all seems fine but after about 30 minutes I've got a plenty of EAGAINs when doing read()'s and trying to read back the data. When I rmmod and insmod the cdc_acm module again, then the situation is starting over again: running ok shortly after load, and more time it is running, more EAGAINs I have when calling read(). As a bonus I can see the problem on the device itself: The device is configured as you can see here on this screen [3]. It has two transmision LEDs: TX and RX. Blink duration is set for 100ms. This is a recording before the bad commit when all is working fine: [4] And this is with the bad commit: [5] As you can see the TX led is blinking wrongly long (indicating transmission?) and I have problems doing read() calls (EAGAIN). Reported-by: Mariusz Bialonczyk <manio@skyboo.net> Signed-off-by: Oliver Neukum <oneukum@suse.com> Fixes: `a81cf9799a` ("cdc-acm: implement put_char() and flush_chars()") Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2018-09-10 20:40:29 +02:00
arch	ARM: SoC fixes	2018-09-02 10:44:28 -07:00
block	block: bsg: move atomic_t ref_count variable to refcount API	2018-08-27 19:17:02 -06:00
certs	export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR()	2018-08-22 23:21:44 +09:00
crypto	DMAengine updates for v4.19-rc1	2018-08-18 15:55:59 -07:00
Documentation	linux-watchdog 4.19-rc2 tag	2018-09-01 13:17:15 -07:00
drivers	Revert "cdc-acm: implement put_char() and flush_chars()"	2018-09-10 20:40:29 +02:00
firmware	kbuild: remove all dummy assignments to obj-	2017-11-18 11:46:06 +09:00
fs	Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-09-02 09:41:45 -07:00
include	linux/mod_devicetable.h: fix kernel-doc missing notation for typec_device_id	2018-09-05 14:36:53 +02:00
init	Kbuild updates for v4.19 (2nd)	2018-08-25 13:40:38 -07:00
ipc	ipc/util.c: update return value of ipc_getref from int to bool	2018-08-22 10:52:52 -07:00
kernel	Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-09-02 10:09:35 -07:00
lib	Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-09-02 09:41:45 -07:00
LICENSES	LICENSES: Add Linux-OpenIB license text	2018-04-27 16:41:53 -06:00
mm	notifier: Remove notifier header file wherever not used	2018-08-30 12:56:40 +02:00
net	Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-09-02 09:41:45 -07:00
samples	samples/bpf: all XDP samples should unload xdp/bpf prog on SIGTERM	2018-08-16 21:55:32 +02:00
scripts	Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2018-09-02 10:11:30 -07:00
security	+ Cleanups	2018-08-24 13:00:33 -07:00
sound	Merge branch 'akpm' (patches from Andrew)	2018-08-23 19:20:12 -07:00
tools	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2018-08-27 11:59:39 -07:00
usr	initramfs: move gen_initramfs_list.sh from scripts/ to usr/	2018-08-22 23:21:44 +09:00
virt	ARM: Support for Group0 interrupts in guests, Cache management	2018-08-22 13:52:44 -07:00
.clang-format	clang-format: Set IndentWrappedFunctionNames false	2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	Kbuild updates for v4.17 (2nd)	2018-04-15 17:21:30 -07:00
.mailmap	libnvdimm-for-4.19_misc	2018-08-25 18:13:10 -07:00
COPYING	COPYING: use the new text with points to the license files	2018-03-23 12:41:45 -06:00
CREDITS	9p: remove Ron Minnich from MAINTAINERS	2018-08-17 16:20:26 -07:00
Kbuild	Kbuild updates for v4.15	2017-11-17 17:45:29 -08:00
Kconfig	kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt	2018-08-02 08:06:55 +09:00
MAINTAINERS	Fix up libata MAINTAINERS entry	2018-08-27 08:07:25 -07:00
Makefile	Linux 4.19-rc2	2018-09-02 14:37:30 -07:00
README	Docs: Added a pointer to the formatted docs to README	2018-03-21 09:02:53 -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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.