svn commit: r324863 - in head/sys: kern sys

[Hans Petter Selasky]

On 10/22/17 15:42, Mateusz Guzik wrote:
> Author: mjg
> Date: Sun Oct 22 13:42:56 2017
> New Revision: 324863
> URL: https://svnweb.freebsd.org/changeset/base/324863
> 
> Log:
>    Change kdb_active type to u_char.
>    
>    Fixes warnings from gcc and keeps the small size. Perhaps nesting should be moved
>    to another variablle.
>    
>    Reported by:	ngie
> 
> Modified:
>    head/sys/kern/subr_kdb.c
>    head/sys/sys/kdb.h
> 
> Modified: head/sys/kern/subr_kdb.c
> ==============================================================================
> --- head/sys/kern/subr_kdb.c	Sun Oct 22 12:12:52 2017	(r324862)
> +++ head/sys/kern/subr_kdb.c	Sun Oct 22 13:42:56 2017	(r324863)
> @@ -50,7 +50,7 @@ __FBSDID("$FreeBSD$");
>   #include <machine/smp.h>
>   #endif
>   
> -bool __read_frequently kdb_active = 0;
> +u_char __read_frequently kdb_active = 0;
>   static void *kdb_jmpbufp = NULL;
>   struct kdb_dbbe *kdb_dbbe = NULL;
>   static struct pcb kdb_pcb;
> 
> Modified: head/sys/sys/kdb.h
> ==============================================================================
> --- head/sys/sys/kdb.h	Sun Oct 22 12:12:52 2017	(r324862)
> +++ head/sys/sys/kdb.h	Sun Oct 22 13:42:56 2017	(r324863)
> @@ -59,7 +59,7 @@ struct kdb_dbbe {
>   	};						\
>   	DATA_SET(kdb_dbbe_set, name##_dbbe)
>   
> -extern bool kdb_active;			/* Non-zero while in debugger. */
> +extern u_char kdb_active;		/* Non-zero while in debugger. */
>   extern int debugger_on_panic;		/* enter the debugger on panic. */
>   extern struct kdb_dbbe *kdb_dbbe;	/* Default debugger backend or NULL. */
>   extern struct trapframe *kdb_frame;	/* Frame to kdb_trap(). */
> 
> 

Should we add __aligned(8) to this definition?

./systm.h:#define	__read_frequently	__section(".data.read_frequently")

It will prevent commonly read variables from residing in two different 
cache-lines on x86 and amd64 at least???


--HPS