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'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>
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>
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>
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>
The contents of this directory is mostly driver-api stuff. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details you should have received a copy of the gnu general public license along with this program if not write to the free software foundation inc 59 temple place suite 330 boston ma 02111 1307 usa extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 1334 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Reviewed-by: Richard Fontana <rfontana@redhat.com> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070033.113240726@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The converted files are focused at the Kernel internal API, so, this is a good candidate for the kernel API set of books. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In the static inline function uart_handle_break() in serial_core.h we dereference port->cons. That gives an error unless console.h is also included. This error hasn't shown up till now because everyone who has defined SUPPORT_SYSRQ has also included console.h, but it's a bit ugly to make this requirement. Let's make the include explicit. Signed-off-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Right now serial drivers process sysrq keys deep in their character
receiving code. This means that they've already grabbed their
port->lock spinlock. This can end up getting in the way if we've go
to do serial stuff (especially kgdb) in response to the sysrq.
Serial drivers have various hacks in them to handle this. Looking at
'8250_port.c' you can see that the console_write() skips locking if
we're in the sysrq handler. Looking at 'msm_serial.c' you can see
that the port lock is dropped around uart_handle_sysrq_char().
It turns out that these hacks aren't exactly perfect. If you have
lockdep turned on and use something like the 8250_port hack you'll get
a splat that looks like:
WARNING: possible circular locking dependency detected
[...] is trying to acquire lock:
... (console_owner){-.-.}, at: console_unlock+0x2e0/0x5e4
but task is already holding lock:
... (&port_lock_key){-.-.}, at: serial8250_handle_irq+0x30/0xe4
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&port_lock_key){-.-.}:
_raw_spin_lock_irqsave+0x58/0x70
serial8250_console_write+0xa8/0x250
univ8250_console_write+0x40/0x4c
console_unlock+0x528/0x5e4
register_console+0x2c4/0x3b0
uart_add_one_port+0x350/0x478
serial8250_register_8250_port+0x350/0x3a8
dw8250_probe+0x67c/0x754
platform_drv_probe+0x58/0xa4
really_probe+0x150/0x294
driver_probe_device+0xac/0xe8
__driver_attach+0x98/0xd0
bus_for_each_dev+0x84/0xc8
driver_attach+0x2c/0x34
bus_add_driver+0xf0/0x1ec
driver_register+0xb4/0x100
__platform_driver_register+0x60/0x6c
dw8250_platform_driver_init+0x20/0x28
...
-> #0 (console_owner){-.-.}:
lock_acquire+0x1e8/0x214
console_unlock+0x35c/0x5e4
vprintk_emit+0x230/0x274
vprintk_default+0x7c/0x84
vprintk_func+0x190/0x1bc
printk+0x80/0xa0
__handle_sysrq+0x104/0x21c
handle_sysrq+0x30/0x3c
serial8250_read_char+0x15c/0x18c
serial8250_rx_chars+0x34/0x74
serial8250_handle_irq+0x9c/0xe4
dw8250_handle_irq+0x98/0xcc
serial8250_interrupt+0x50/0xe8
...
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&port_lock_key);
lock(console_owner);
lock(&port_lock_key);
lock(console_owner);
*** DEADLOCK ***
The hack used in 'msm_serial.c' doesn't cause the above splats but it
seems a bit ugly to unlock / lock our spinlock deep in our irq
handler.
It seems like we could defer processing the sysrq until the end of the
interrupt handler right after we've unlocked the port. With this
scheme if a whole batch of sysrq characters comes in one irq then we
won't handle them all, but that seems like it should be a fine
compromise.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>