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Use a new message buffer `consmsgbuf' to forward messages to a

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TIOCCONS console (e.g. xconsole) via a timeout routine instead of
calling into the tty code directly from printf(). This fixes a
number of cases where calling printf() at the wrong time (such as
with locks held) would cause a panic if xconsole is running.

The TIOCCONS message buffer is 8k in size by default, but this can
be changed with the kern.consmsgbuf_size sysctl. By default, messages
are checked for 5 times per second. The timer runs and the buffer
memory remains allocated only at times when a TIOCCONS console is
active.

Discussed on:	freebsd-arch
This commit is contained in:
Ian Dowse 2003-06-22 02:54:33 +00:00
parent 7ca33ad1e8
commit d29bf12ff8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=116663
4 changed files with 89 additions and 16 deletions
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26
sys/kern/subr_prf.c
View File

@ -89,9 +89,6 @@ struct snprintf_arg {
extern int log_open;
struct tty *constty; /* pointer to console "window" tty */
static void (*v_putc)(int) = cnputc; /* routine to putc on virtual console */
static void msglogchar(int c, int pri);
static void putchar(int ch, void *arg);
static char *ksprintn(char *nbuf, uintmax_t num, int base, int *len);
@ -335,21 +332,24 @@ static void
putchar(int c, void *arg)
{
struct putchar_arg *ap = (struct putchar_arg*) arg;
int flags = ap->flags;
struct tty *tp = ap->tty;
int consdirect, flags = ap->flags;
consdirect = ((flags & TOCONS) && constty == NULL);
/* Don't use the tty code after a panic. */
if (panicstr)
constty = NULL;
if ((flags & TOCONS) && tp == NULL && constty) {
tp = constty;
flags |= TOTTY;
consdirect = 1;
if (consdirect) {
if (c != '\0')
cnputc(c);
} else {
if ((flags & TOTTY) && tp != NULL)
tputchar(c, tp);
if ((flags & TOCONS) && constty != NULL)
msgbuf_addchar(&consmsgbuf, c);
}
if ((flags & TOTTY) && tp && tputchar(c, tp) < 0 &&
(flags & TOCONS) && tp == constty)
constty = NULL;
if ((flags & TOLOG))
msglogchar(c, ap->pri);
if ((flags & TOCONS) && constty == NULL && c != '\0')
(*v_putc)(c);
}
/*

6
sys/kern/tty.c
View File

@ -261,7 +261,7 @@ ttyclose(struct tty *tp)
funsetown(&tp->t_sigio);
s = spltty();
if (constty == tp)
constty = NULL;
constty_clear();
ttyflush(tp, FREAD | FWRITE);
clist_free_cblocks(&tp->t_canq);
@ -871,9 +871,9 @@ ttioctl(struct tty *tp, u_long cmd, void *data, int flag)
if (error)
return (error);
constty = tp;
constty_set(tp);
} else if (tp == constty)
constty = NULL;
constty_clear();
break;
case TIOCDRAIN: /* wait till output drained */
error = ttywait(tp);

70
sys/kern/tty_cons.c
View File

@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/msgbuf.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/queue.h>
@ -117,11 +118,16 @@ int cons_unavail = 0; /* XXX:
static int cn_mute;
static int openflag; /* how /dev/console was opened */
static int cn_is_open;
static char *consbuf; /* buffer used by `consmsgbuf' */
static struct callout conscallout; /* callout for outputting to constty */
struct msgbuf consmsgbuf; /* message buffer for console tty */
static u_char console_pausing; /* pause after each line during probe */
static char *console_pausestr=
"<pause; press any key to proceed to next line or '.' to end pause mode>";
struct tty *constty; /* pointer to console "window" tty */
void cndebug(char *);
static void constty_timeout(void *arg);
CONS_DRIVER(cons, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
SET_DECLARE(cons_set, struct consdev);
@ -589,6 +595,70 @@ cndbctl(int on)
refcount++;
}
static int consmsgbuf_size = 8192;
SYSCTL_INT(_kern, OID_AUTO, consmsgbuf_size, CTLFLAG_RW, &consmsgbuf_size, 0,
"");
/*
* Redirect console output to a tty.
*/
void
constty_set(struct tty *tp)
{
int size;
KASSERT(tp != NULL, ("constty_set: NULL tp"));
if (consbuf == NULL) {
size = consmsgbuf_size;
consbuf = malloc(size, M_TTYS, M_WAITOK);
msgbuf_init(&consmsgbuf, consbuf, size);
callout_init(&conscallout, 0);
}
constty = tp;
constty_timeout(NULL);
}
/*
* Disable console redirection to a tty.
*/
void
constty_clear(void)
{
int c;
constty = NULL;
if (consbuf == NULL)
return;
callout_stop(&conscallout);
while ((c = msgbuf_getchar(&consmsgbuf)) != -1)
cnputc(c);
free(consbuf, M_TTYS);
consbuf = NULL;
}
/* Times per second to check for pending console tty messages. */
static int constty_wakeups_per_second = 5;
SYSCTL_INT(_kern, OID_AUTO, constty_wakeups_per_second, CTLFLAG_RW,
&constty_wakeups_per_second, 0, "");
static void
constty_timeout(void *arg)
{
int c;
while (constty != NULL && (c = msgbuf_getchar(&consmsgbuf)) != -1) {
if (tputchar(c, constty) < 0)
constty = NULL;
}
if (constty != NULL) {
callout_reset(&conscallout, hz / constty_wakeups_per_second,
constty_timeout, NULL);
} else {
/* Deallocate the constty buffer memory. */
constty_clear();
}
}
static void
cn_drvinit(void *unused)
{

3
sys/sys/tty.h
View File

@ -265,6 +265,7 @@ struct speedtab {
#ifdef MALLOC_DECLARE
MALLOC_DECLARE(M_TTYS);
#endif
extern struct msgbuf consmsgbuf; /* Message buffer for constty. */
extern struct tty *constty; /* Temporary virtual console. */
extern long tk_cancc;
extern long tk_nin;
@ -275,6 +276,8 @@ int b_to_q(char *cp, int cc, struct clist *q);
void catq(struct clist *from, struct clist *to);
void clist_alloc_cblocks(struct clist *q, int ccmax, int ccres);
void clist_free_cblocks(struct clist *q);
void constty_set(struct tty *tp);
void constty_clear(void);
int getc(struct clist *q);
void ndflush(struct clist *q, int cc);
char *nextc(struct clist *q, char *cp, int *c);