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a9c3f68f3c
linux_dsm_epyc7002/drivers/usb/gadget
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Peter Hurley a9c3f68f3c tty: Fix low_latency BUG 
The user-settable knob, low_latency, has been the source of
several BUG reports which stem from flush_to_ldisc() running
in interrupt context. Since 3.12, which added several sleeping
locks (termios_rwsem and buf->lock) to the input processing path,
the frequency of these BUG reports has increased.

Note that changes in 3.12 did not introduce this regression;
sleeping locks were first added to the input processing path
with the removal of the BKL from N_TTY in commit
a88a69c912,
'n_tty: Fix loss of echoed characters and remove bkl from n_tty'
and later in commit 38db89799b,
'tty: throttling race fix'. Since those changes, executing
flush_to_ldisc() in interrupt_context (ie, low_latency set), is unsafe.

However, since most devices do not validate if the low_latency
setting is appropriate for the context (process or interrupt) in
which they receive data, some reports are due to misconfiguration.
Further, serial dma devices for which dma fails, resort to
interrupt receiving as a backup without resetting low_latency.

Historically, low_latency was used to force wake-up the reading
process rather than wait for the next scheduler tick. The
effect was to trim multiple milliseconds of latency from
when the process would receive new data.

Recent tests [1] have shown that the reading process now receives
data with only 10's of microseconds latency without low_latency set.

Remove the low_latency rx steering from tty_flip_buffer_push();
however, leave the knob as an optional hint to drivers that can
tune their rx fifos and such like. Cleanup stale code comments
regarding low_latency.

[1] https://lkml.org/lkml/2014/2/20/434

"Yay.. thats an annoying historical pain in the butt gone."
	-- Alan Cox

Reported-by: Beat Bolli <bbolli@ewanet.ch>
Reported-by: Pavel Roskin <proski@gnu.org>
Acked-by: David Sterba <dsterba@suse.cz>
Cc: Grant Edwards <grant.b.edwards@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Hal Murray <murray+fedora@ip-64-139-1-69.sjc.megapath.net>
Cc: <stable@vger.kernel.org> # 3.12.x+
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-02-28 16:31:00 -08:00
..
acm_ms.c usb: gadget: fix up some comments about CONFIG_USB_DEBUG 2013-12-20 09:51:24 -06:00
amd5536udc.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
amd5536udc.h usb: gadget: amd5536udc: remove unused structure member 2013-03-18 11:16:56 +02:00
at91_udc.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
at91_udc.h usb: gadget: at91_udc: add usb_clk for transition to common clk framework 2013-08-02 15:17:03 +03:00
atmel_usba_udc.c ARM: SoC cleanups for 3.14 2014-01-23 18:36:55 -08:00
atmel_usba_udc.h USB: gadget: atmel_usba: add DT support 2013-05-24 07:14:45 +08:00
audio.c
bcm63xx_udc.c usb: gadget: bcm63xx_udc: fix build failure on DMA channel code 2014-02-18 10:34:54 -06:00
cdc2.c usb: gadget: cdc2: fix conversion to new interface of f_ecm 2013-09-17 10:38:52 -05:00
composite.c usb: gadget: should use u16 type variable to store MaxPower 2013-12-19 09:27:43 -06:00
config.c
configfs.c usb: gadget: configfs: include appropriate header file in configfs.c 2013-12-19 09:27:42 -06:00
configfs.h usb: gadget: configfs: add a method to unregister the gadget 2013-10-01 09:50:22 -05:00
dbgp.c
dummy_hcd.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
epautoconf.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
ether.c usb: gadget: ether: put_usb_function on unbind 2013-07-25 20:35:23 +03:00
f_acm.c usb: acm gadget: Null termintate strings table 2013-08-30 11:10:36 -07:00
f_ecm.c usb: gadget: f_ecm: remove compatibility layer 2013-12-12 13:43:36 -06:00
f_eem.c usb: gadget: f_eem: Staticize eem_alloc 2013-09-17 11:06:50 -05:00
f_fs.c usb: gadget: fix NULL pointer dereference 2014-02-20 09:17:23 -06:00
f_hid.c usb: gadget: factor out alloc_ep_req 2013-11-26 13:41:32 -06:00
f_loopback.c usb: gadget: f_loopback: Fix sparse warning 2013-12-17 13:17:42 -06:00
f_mass_storage.c usb: gadget: f_mass_storage: Fix sparse warning 2013-12-17 13:17:43 -06:00
f_mass_storage.h usb: gadget: f_mass_storage: remove compatibility layer 2013-10-10 10:24:53 -05:00
f_midi.c usb: gadget: factor out alloc_ep_req 2013-11-26 13:41:32 -06:00
f_ncm.c usb: gadget: f_ncm: Fix sparse warning 2013-12-17 13:17:43 -06:00
f_obex.c usb: gadget: f_obex: Fix sparse warning 2013-12-17 13:17:43 -06:00
f_phonet.c usb: gadget: f_phonet: Fix sparse warning 2013-12-17 13:17:44 -06:00
f_rndis.c usb: gadget: rndis: merge u_rndis.ko with usb_f_rndis.ko 2013-12-12 13:43:38 -06:00
f_serial.c usb: gadget: f_serial: Fix sparse warning 2013-12-17 13:17:44 -06:00
f_sourcesink.c usb: gadget: f_sourcesink: Fix sparse warning 2013-12-17 13:17:44 -06:00
f_subset.c usb: gadget: f_subset: remove compatibility layer 2013-12-12 13:43:37 -06:00
f_uac1.c usb: gadget: f_uac1: Staticize local functions 2013-08-09 16:34:19 +03:00
f_uac2.c USB: gadget: f_uac2: Fix broken prm to uac2 mapping 2013-06-10 17:10:23 +03:00
f_uvc.c Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media 2013-07-13 12:09:57 -07:00
f_uvc.h usb: gadget: uvc: Fix coding style issues introduced by SS support 2013-03-18 11:18:18 +02:00
fotg210-udc.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
fotg210.h usb: gadget: add Faraday fotg210_udc driver 2013-06-10 17:58:11 +03:00
fsl_mxc_udc.c usb: gadget: use dev_get_platdata() 2013-07-30 11:18:46 +03:00
fsl_qe_udc.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
fsl_qe_udc.h
fsl_udc_core.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
fsl_usb2_udc.h
functions.c
fusb300_udc.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
fusb300_udc.h usb: gadget: fusb300_udc: add FUSB300_EPSET0_STL_CLR for clearing EP0 stall 2013-04-02 16:57:24 +03:00
g_ffs.c usb: gadget: g_ffs: convert to new interface of f_fs 2013-12-12 13:43:39 -06:00
g_zero.h usb: gadget: f_sourcesink: add configfs support 2013-11-26 13:47:41 -06:00
gadget_chips.h
gmidi.c
goku_udc.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
goku_udc.h usb: gadget: goku_udc: let udc-core manage gadget->dev 2013-03-18 11:16:45 +02:00
gr_udc.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
gr_udc.h usb: gadget: Add UDC driver for Aeroflex Gaisler GRUSBDC 2013-12-23 19:26:13 -06:00
hid.c usb: gadget: use dev_get_platdata() 2013-07-30 11:18:46 +03:00
inode.c Merge git://git.kvack.org/~bcrl/aio-next 2013-09-13 10:55:58 -07:00
Kconfig usb: gadget: Add UDC driver for Aeroflex Gaisler GRUSBDC 2013-12-23 19:26:13 -06:00
lpc32xx_udc.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
m66592-udc.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
m66592-udc.h
Makefile usb: gadget: Add UDC driver for Aeroflex Gaisler GRUSBDC 2013-12-23 19:26:13 -06:00
mass_storage.c usb: gadget: mass_storage: convert to new interface of f_mass_storage 2013-10-10 10:24:10 -05:00
multi.c usb: gadget: fix up some comments about CONFIG_USB_DEBUG 2013-12-20 09:51:24 -06:00
mv_u3d_core.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
mv_u3d.h
mv_udc_core.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
mv_udc.h usb: gadget: mv_udc_core: remove unused clock 2013-04-02 11:42:45 +03:00
ncm.c usb: gadget: ncm: convert to new function interface 2013-06-10 17:12:52 +03:00
ndis.h
net2272.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
net2272.h
net2280.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
net2280.h
nokia.c usb: gadget: nokia: fix error recovery path for optional functions 2013-12-17 13:17:41 -06:00
omap_udc.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
omap_udc.h
pch_udc.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
printer.c usb: gadget: printer: using gadget_is_otg to check otg support at runtime 2014-02-20 09:17:22 -06:00
pxa25x_udc.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
pxa25x_udc.h usb: gadget: pxa25x_udc: convert to udc_start/udc_stop 2013-01-24 21:11:31 +02:00
pxa27x_udc.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
pxa27x_udc.h usb: gadget: pxa27x_udc: convert to udc_start/udc_stop 2013-01-24 21:11:31 +02:00
r8a66597-udc.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
r8a66597-udc.h
rndis.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
rndis.h usb: gadget: rndis: init & exit rndis at module load/unload 2013-06-10 17:58:09 +03:00
s3c2410_udc.c usb: gadget: s3c2410_udc: Fix build error 2014-02-18 10:34:04 -06:00
s3c2410_udc.h usb: gadget: s3c2410: convert to udc_start/udc_stop 2013-01-24 21:11:32 +02:00
s3c-hsotg.c usb: gadget: s3c-hsotg: remove duplicated include from s3c-hsotg.c 2014-01-07 16:30:10 -08:00
s3c-hsotg.h usb: gadget: s3c-hsotg: get phy bus width from phy subsystem 2013-12-23 14:31:49 -06:00
s3c-hsudc.c usb: gadget: add "maxpacket_limit" field to struct usb_ep 2013-12-17 13:17:41 -06:00
serial.c usb: gadget: serial: convert to new interface of f_obex 2013-04-03 14:43:36 +03:00
storage_common.c usb: gadget: storage_common: pass filesem to fsg_store_cdrom 2013-10-15 06:52:08 -05:00
storage_common.h usb: gadget: mass storage: fix return of delayed status 2013-11-25 10:56:33 -06:00
tcm_usb_gadget.c usb: gadget: tcm_usb_gadget: mark bot_cleanup_old_alt static 2013-11-25 11:19:41 -06:00
tcm_usb_gadget.h
u_ecm.h usb: gadget: f_ecm: add configfs support 2013-06-10 17:27:54 +03:00
u_eem.h usb: gadget: f_eem: add configfs support 2013-06-10 17:58:00 +03:00
u_ether_configfs.h usb: gadget: add helpers for configfs support for USB Ethernet 2013-06-10 17:15:43 +03:00
u_ether.c usb: gadget: update some out of date comments 2013-11-26 10:58:17 -06:00
u_ether.h usb: gadget: f_rndis: remove compatibility layer 2013-12-12 13:43:37 -06:00
u_f.c usb: gadget: factor out alloc_ep_req 2013-11-26 13:41:32 -06:00
u_f.h usb: gadget: factor out alloc_ep_req 2013-11-26 13:41:32 -06:00
u_fs.h usb: gadget: FunctionFS: add configfs support 2013-12-12 13:43:40 -06:00
u_gether.h usb: gadget: f_subset: add configfs support 2013-06-10 17:58:08 +03:00
u_ncm.h usb: gadget: f_ncm: add configfs support 2013-06-10 17:15:02 +03:00
u_phonet.h usb: gadget: f_phonet: remove compatibility layer 2013-06-10 17:31:55 +03:00
u_rndis.h usb: gadget: rndis: merge u_rndis.ko with usb_f_rndis.ko 2013-12-12 13:43:38 -06:00
u_serial.c tty: Fix low_latency BUG 2014-02-28 16:31:00 -08:00
u_serial.h usb: gadget: nokia: use function framework for ACM 2013-04-03 14:43:20 +03:00
u_uac1.c usb: gadget: u_uac1: add __user annotation 2013-08-09 16:34:13 +03:00
u_uac1.h
udc-core.c usb: gadget: udc-core: Do not report -EISNAM error from gadgetfs 2013-10-04 09:44:43 -05:00
usbstring.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
uvc_queue.c usb: gadget: uvc: Fix error handling in uvc_queue_buffer() 2013-08-09 17:40:54 +03:00
uvc_queue.h usb: gadget/uvc: Port UVC webcam gadget to use videobuf2 framework 2013-04-02 11:42:48 +03:00
uvc_v4l2.c usb: gadget/uvc: Add support for 'get_unmapped_area' for MMUless architectures 2013-04-02 11:42:49 +03:00
uvc_video.c usb: gadget/uvc: Port UVC webcam gadget to use videobuf2 framework 2013-04-02 11:42:48 +03:00
uvc.h [media] f_uvc: add v4l2_device and replace parent with v4l2_dev 2013-06-21 11:04:47 -03:00
webcam.c
zero.c Linux 3.13-rc4 2013-12-19 09:18:53 -06:00