linux-stable.git/include/linux/serial_core.h, branch v5.7.17 Linux kernel stable tree serial: core: fix sysrq overhead regression 2020-07-22T07:34:20+00:00 Johan Hovold johan@kernel.org 2020-06-10T15:22:31+00:00 cbf6751750400deb9c95d591ebf6b878af0af23b commit 08d5470308ac3598e7709d08b8979ce6e9de8da2 upstream. Commit 8e20fc391711 ("serial_core: Move sysrq functions from header file") converted the inline sysrq helpers to exported functions which are now called for every received character, interrupt and break signal also on systems without CONFIG_MAGIC_SYSRQ_SERIAL instead of being optimised away by the compiler. Inlining these helpers again also avoids the function call overhead when CONFIG_MAGIC_SYSRQ_SERIAL is enabled (e.g. when the port is not used as a console). Fixes: 8e20fc391711 ("serial_core: Move sysrq functions from header file") Cc: Dmitry Safonov <0x7f454c46@gmail.com> Signed-off-by: Johan Hovold <johan@kernel.org> Cc: stable <stable@vger.kernel.org> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com> Link: https://lore.kernel.org/r/20200610152232.16925-3-johan@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 08d5470308ac3598e7709d08b8979ce6e9de8da2 upstream.

Commit 8e20fc391711 ("serial_core: Move sysrq functions from header
file") converted the inline sysrq helpers to exported functions which
are now called for every received character, interrupt and break signal
also on systems without CONFIG_MAGIC_SYSRQ_SERIAL instead of being
optimised away by the compiler.

Inlining these helpers again also avoids the function call overhead when
CONFIG_MAGIC_SYSRQ_SERIAL is enabled (e.g. when the port is not used as
a console).

Fixes: 8e20fc391711 ("serial_core: Move sysrq functions from header file")
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Link: https://lore.kernel.org/r/20200610152232.16925-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Revert "serial: core: Refactor uart_unlock_and_check_sysrq()" 2020-07-22T07:34:20+00:00 Johan Hovold johan@kernel.org 2020-06-10T15:22:30+00:00 04dcaed0440631ea79d160550b6006c2303a0dd5 commit 10652a9e9fe3fbcaca090f99cd3060ac3fee2913 upstream. This reverts commit da9a5aa3402db0ff3b57216d8dbf2478e1046cae. In order to ease backporting a fix for a sysrq regression, revert this rewrite which was since added on top. The other sysrq helpers now bail out early when sysrq is not enabled; it's better to keep that pattern here as well. Note that the __releases() attribute won't be needed after the follow-on fix either. Fixes: da9a5aa3402d ("serial: core: Refactor uart_unlock_and_check_sysrq()") Cc: stable <stable@vger.kernel.org> Signed-off-by: Johan Hovold <johan@kernel.org> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Link: https://lore.kernel.org/r/20200610152232.16925-2-johan@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 10652a9e9fe3fbcaca090f99cd3060ac3fee2913 upstream.

This reverts commit da9a5aa3402db0ff3b57216d8dbf2478e1046cae.

In order to ease backporting a fix for a sysrq regression, revert this
rewrite which was since added on top.

The other sysrq helpers now bail out early when sysrq is not enabled;
it's better to keep that pattern here as well.

Note that the __releases() attribute won't be needed after the follow-on
fix either.

Fixes: da9a5aa3402d ("serial: core: Refactor uart_unlock_and_check_sysrq()")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200610152232.16925-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
serial: core: Refactor uart_unlock_and_check_sysrq() 2020-03-12T16:16:42+00:00 Andy Shevchenko andriy.shevchenko@linux.intel.com 2020-03-10T17:43:37+00:00 da9a5aa3402db0ff3b57216d8dbf2478e1046cae Refactor uart_unlock_and_check_sysrq() to: - explicitly show that we release a port lock which makes static analyzers happy: CHECK drivers/tty/serial/serial_core.c .../serial_core.c:3290:17: warning: context imbalance in 'uart_unlock_and_check_sysrq' - unexpected unlock - use flags instead of irqflags to avoid confusion with IRQ flags - provide one return point - be more compact Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com> Link: https://lore.kernel.org/r/20200310174337.74109-4-andriy.shevchenko@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Refactor uart_unlock_and_check_sysrq() to:

  - explicitly show that we release a port lock which makes
    static analyzers happy:

CHECK   drivers/tty/serial/serial_core.c
.../serial_core.c:3290:17: warning: context imbalance in 'uart_unlock_and_check_sysrq' - unexpected unlock

  - use flags instead of irqflags to avoid confusion with IRQ flags

  - provide one return point

  - be more compact

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Link: https://lore.kernel.org/r/20200310174337.74109-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE 2020-03-07T08:52:02+00:00 Dmitry Safonov dima@arista.com 2020-03-02T17:51:35+00:00 68af43173d3fcece70bef49cb992c64c4c68ff23 Many embedded boards have a disconnected TTL level serial which can generate some garbage that can lead to spurious false sysrq detects. Currently, sysrq can be either completely disabled for serial console or always disabled (with CONFIG_MAGIC_SYSRQ_SERIAL), since commit 732dbf3a6104 ("serial: do not accept sysrq characters via serial port") At Arista, we have such boards that can generate BREAK and random garbage. While disabling sysrq for serial console would solve the problem with spurious false sysrq triggers, it's also desirable to have a way to enable sysrq back. As a measure of balance between on and off options, add MAGIC_SYSRQ_SERIAL_SEQUENCE which is a string sequence that can enable sysrq if it follows BREAK on a serial line. The longer the string - the less likely it may be in the garbage. Having the way to enable sysrq was beneficial to debug lockups with a manual investigation in field and on the other side preventing false sysrq detections. Based-on-patch-by: Vasiliy Khoruzhick <vasilykh@arista.com> Signed-off-by: Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20200302175135.269397-3-dima@arista.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Many embedded boards have a disconnected TTL level serial which can
generate some garbage that can lead to spurious false sysrq detects.

Currently, sysrq can be either completely disabled for serial console
or always disabled (with CONFIG_MAGIC_SYSRQ_SERIAL), since
commit 732dbf3a6104 ("serial: do not accept sysrq characters via serial port")

At Arista, we have such boards that can generate BREAK and random
garbage. While disabling sysrq for serial console would solve
the problem with spurious false sysrq triggers, it's also desirable
to have a way to enable sysrq back.

As a measure of balance between on and off options, add
MAGIC_SYSRQ_SERIAL_SEQUENCE which is a string sequence that can enable
sysrq if it follows BREAK on a serial line. The longer the string - the
less likely it may be in the garbage.

Having the way to enable sysrq was beneficial to debug lockups with
a manual investigation in field and on the other side preventing false
sysrq detections.

Based-on-patch-by: Vasiliy Khoruzhick <vasilykh@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200302175135.269397-3-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
serial_core: Remove unused member in uart_port 2020-01-15T12:39:14+00:00 Dmitry Safonov dima@arista.com 2020-01-14T17:19:12+00:00 7788f549ed8cfbecd75c10e1a1988812adba49d8 It should remove the align-padding before @name. [yes, there's a "hole" in the structure now, but that's fine, no one cares. If they do care, the whole thing should be restructured using pahole to find a better ordering. Removing this field is good as some drivers have been known to abuse it for other things when they shouldn't have been doing that. -- gregkh] Signed-off-by: Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20200114171912.261787-4-dima@arista.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
It should remove the align-padding before @name.

[yes, there's a "hole" in the structure now, but that's fine, no one
cares.  If they do care, the whole thing should be restructured using
pahole to find a better ordering.  Removing this field is good as some
drivers have been known to abuse it for other things when they shouldn't
have been doing that. -- gregkh]

Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200114171912.261787-4-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
serial_core: Move sysrq functions from header file 2020-01-10T16:48:02+00:00 Dmitry Safonov dima@arista.com 2020-01-09T21:54:42+00:00 8e20fc3917117b42de316e87f073a1ca43d94c9f It's not worth to have them in every serial driver and I'm about to add another helper function. Signed-off-by: Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20200109215444.95995-2-dima@arista.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
It's not worth to have them in every serial driver and I'm about to add
another helper function.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200109215444.95995-2-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
serial_core: Remove SUPPORT_SYSRQ ifdeffery 2019-12-18T14:05:11+00:00 Dmitry Safonov dima@arista.com 2019-12-13T00:06:53+00:00 82cfd2e62b354840af6a045e084f6e9e7c49584d No one defines it anymore. Signed-off-by: Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20191213000657.931618-55-dima@arista.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
No one defines it anymore.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20191213000657.931618-55-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
serial_core: Un-ifdef sysrq SUPPORT_SYSRQ 2019-12-17T14:10:17+00:00 Dmitry Safonov dima@arista.com 2019-12-13T00:06:02+00:00 1997e9dfdc84c8f73d6fc318355cf9e313aba183 The SUPPORT_SYSRQ is messy: every .c source should define it before including "serial_core.h" if sysrq is supported or struct uart_port will differ in sizes. Also this prevents moving to serial_core.c functions: uart_handle_sysrq_char(), uart_prepare_sysrq_char(), uart_unlock_and_check_sysrq(). It doesn't save many bytes in the structure, and a better way to reduce it's size would be making rs485 and iso7816 pointers. Introduce `has_sysrq` member to be used by serial line drivers further. Signed-off-by: Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20191213000657.931618-4-dima@arista.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
The SUPPORT_SYSRQ is messy: every .c source should define it before
including "serial_core.h" if sysrq is supported or struct uart_port will
differ in sizes. Also this prevents moving to serial_core.c functions:
uart_handle_sysrq_char(), uart_prepare_sysrq_char(),
uart_unlock_and_check_sysrq().

It doesn't save many bytes in the structure, and a better way to reduce
it's size would be making rs485 and iso7816 pointers.

Introduce `has_sysrq` member to be used by serial line drivers further.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20191213000657.931618-4-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
serial: Move sysrq members above 2019-12-17T13:48:51+00:00 Dmitry Safonov dima@arista.com 2019-12-13T00:06:01+00:00 7e5ed9f5e012f21a1514edcf8c35b9b4cfbd96c3 At the current place members those follow are: : upf_t flags; : upstat_t status; : int hw_stopped; : unsigned int mctrl; : unsigned int timeout; : unsigned int type; : const struct uart_ops *ops; Together, they give (*ops) 8-byte align on 64-bit platforms. And `sysrq_ch` introduces 4-byte padding. On the other side, above: : struct device *dev; : unsigned char hub6; : unsigned char suspended; : unsigned char unused[2]; : const char *name; Adds another 4-byte padding. Moving sysrq members just before `hub6` allows to save 8 bytes per-uart_port on 64-bit platforms: On my gcc, x86_64 sizeof(struct uart_port) goes from 528 to 520. Signed-off-by: Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20191213000657.931618-3-dima@arista.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
At the current place members those follow are:
:	upf_t			flags;
:	upstat_t		status;
:	int			hw_stopped;
:	unsigned int		mctrl;
:	unsigned int		timeout;
:	unsigned int		type;
:	const struct uart_ops	*ops;

Together, they give (*ops) 8-byte align on 64-bit platforms.
And `sysrq_ch` introduces 4-byte padding.

On the other side, above:
:	struct device		*dev;
:	unsigned char		hub6;
:	unsigned char		suspended;
:	unsigned char		unused[2];
:	const char		*name;

Adds another 4-byte padding.

Moving sysrq members just before `hub6` allows to save 8 bytes
per-uart_port on 64-bit platforms:
On my gcc, x86_64 sizeof(struct uart_port) goes from 528 to 520.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20191213000657.931618-3-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
docs: serial: move it to the driver-api 2019-07-15T14:03:03+00:00 Mauro Carvalho Chehab mchehab+samsung@kernel.org 2019-06-27T19:31:35+00:00 65388dad1bbb51a4eb6cc91b9fa865b57646fb67 The contents of this directory is mostly driver-api stuff. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> 
The contents of this directory is mostly driver-api stuff.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>