serial: Move sysrq members above

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>

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 2b78cc7..bbbe57b 100644 (file)
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -161,11 +161,6 @@ struct uart_port {
        struct uart_icount      icount;                 /* statistics */
 
        struct console          *cons;                  /* struct console, if any */
-#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
-       unsigned long           sysrq;                  /* sysrq timeout */
-       unsigned int            sysrq_ch;               /* char for sysrq */
-#endif
-
        /* flags must be updated while holding port mutex */
        upf_t                   flags;
 
@@ -244,6 +239,12 @@ struct uart_port {
        resource_size_t         mapbase;                /* for ioremap */
        resource_size_t         mapsize;
        struct device           *dev;                   /* parent device */
+
+#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
+       unsigned long           sysrq;                  /* sysrq timeout */
+       unsigned int            sysrq_ch;               /* char for sysrq */
+#endif
+
        unsigned char           hub6;                   /* this should be in the 8250 driver */
        unsigned char           suspended;
        unsigned char           unused[2];