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Add a cnputs() function to write a string to the console with

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a lock to prevent interspersed strings written from different CPUs
at the same time.

To avoid putting a buffer on the stack or having to malloc one,
space is incorporated in the per-cpu structure. The buffer
size if 128 bytes; chosen because it's the next power of 2 size
up from 80 characters.

String writes to the console are buffered up the end of the line
or until the buffer fills. Then the buffer is flushed to all
console devices.

Existing low level console output via cnputc() is unaffected by
this change. ithread calls to log() are also unaffected to avoid
blocking those threads.

A minor change to the behaviour in a panic situation is that
console output will still be buffered, but won't be written to
a tty as before. This should prevent interspersed panic output
as a number of CPUs panic before we end up single threaded
running ddb.

Reviewed by:	scottl, jhb
MFC after:	2 weeks
This commit is contained in:
John Birrell 2006-11-01 04:54:51 +00:00
parent b889a97163
commit 3d068827c2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=163858
10 changed files with 109 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
sys/amd64/amd64/genassym.c
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@ -185,6 +185,7 @@ ASSYM(PC_CURTHREAD, offsetof(struct pcpu, pc_curthread));
ASSYM(PC_FPCURTHREAD, offsetof(struct pcpu, pc_fpcurthread));
ASSYM(PC_IDLETHREAD, offsetof(struct pcpu, pc_idlethread));
ASSYM(PC_CURPCB, offsetof(struct pcpu, pc_curpcb));
ASSYM(PC_CONS_BUFR, offsetof(struct pcpu, pc_cons_bufr));
ASSYM(PC_CPUID, offsetof(struct pcpu, pc_cpuid));
ASSYM(PC_SCRATCH_RSP, offsetof(struct pcpu, pc_scratch_rsp));
ASSYM(PC_CURPMAP, offsetof(struct pcpu, pc_curpmap));

1
sys/arm/arm/genassym.c
View File

@ -69,6 +69,7 @@ ASSYM(PCB_R12, offsetof(struct pcb, un_32.pcb32_r12));
ASSYM(PCB_PC, offsetof(struct pcb, un_32.pcb32_pc));
ASSYM(PCB_SP, offsetof(struct pcb, un_32.pcb32_sp));
ASSYM(PC_CONS_BUFR, offsetof(struct pcpu, pc_cons_bufr));
ASSYM(PC_CURPCB, offsetof(struct pcpu, pc_curpcb));
ASSYM(PC_CURTHREAD, offsetof(struct pcpu, pc_curthread));
ASSYM(M_LEN, offsetof(struct mbuf, m_len));

1
sys/i386/i386/genassym.c
View File

@ -195,6 +195,7 @@ ASSYM(PC_COMMON_TSSD, offsetof(struct pcpu, pc_common_tssd));
ASSYM(PC_TSS_GDT, offsetof(struct pcpu, pc_tss_gdt));
ASSYM(PC_FSGS_GDT, offsetof(struct pcpu, pc_fsgs_gdt));
ASSYM(PC_CURRENTLDT, offsetof(struct pcpu, pc_currentldt));
ASSYM(PC_CONS_BUFR, offsetof(struct pcpu, pc_cons_bufr));
ASSYM(PC_CPUID, offsetof(struct pcpu, pc_cpuid));
ASSYM(PC_CURPMAP, offsetof(struct pcpu, pc_curpmap));
ASSYM(PC_PRIVATE_TSS, offsetof(struct pcpu, pc_private_tss));

1
sys/ia64/ia64/genassym.c
View File

@ -91,6 +91,7 @@ ASSYM(MC_SPECIAL_RNAT, offsetof(mcontext_t, mc_special.rnat));
ASSYM(PAGE_SHIFT, PAGE_SHIFT);
ASSYM(PAGE_SIZE, PAGE_SIZE);
ASSYM(PC_CONS_BUFR, offsetof(struct pcpu, pc_cons_bufr));
ASSYM(PC_CPUID, offsetof(struct pcpu, pc_cpuid));
ASSYM(PC_CURRENT_PMAP, offsetof(struct pcpu, pc_current_pmap));
ASSYM(PC_CURTHREAD, offsetof(struct pcpu, pc_curthread));

89
sys/kern/subr_prf.c
View File

@ -78,6 +78,10 @@ struct putchar_arg {
int flags;
int pri;
struct tty *tty;
char *p_bufr;
size_t n_bufr;
char *p_next;
size_t remain;
};
struct snprintf_arg {
@ -92,7 +96,6 @@ static void putchar(int ch, void *arg);
static char *ksprintn(char *nbuf, uintmax_t num, int base, int *len, int upper);
static void snprintf_func(int ch, void *arg);
static int consintr = 1; /* Ok to handle console interrupts? */
static int msgbufmapped; /* Set when safe to use msgbuf */
int msgbuftrigger;
@ -234,6 +237,7 @@ log(int level, const char *fmt, ...)
pca.tty = NULL;
pca.pri = level;
pca.flags = log_open ? TOLOG : TOCONS;
pca.p_bufr = NULL;
va_start(ap, fmt);
kvprintf(fmt, putchar, &pca, 10, ap);
@ -284,43 +288,96 @@ int
printf(const char *fmt, ...)
{
va_list ap;
int savintr;
struct putchar_arg pca;
int retval;
savintr = consintr; /* disable interrupts */
consintr = 0;
critical_enter();
va_start(ap, fmt);
pca.tty = NULL;
pca.flags = TOCONS | TOLOG;
pca.pri = -1;
pca.p_bufr = (char *) PCPU_PTR(cons_bufr);
pca.p_next = pca.p_bufr;
pca.n_bufr = PCPU_CONS_BUFR;
pca.remain = PCPU_CONS_BUFR;
*pca.p_next = '\0';
retval = kvprintf(fmt, putchar, &pca, 10, ap);
va_end(ap);
/* Write any buffered console output: */
if (*pca.p_bufr != '\0')
cnputs(pca.p_bufr);
if (!panicstr)
msgbuftrigger = 1;
consintr = savintr; /* reenable interrupts */
critical_exit();
return (retval);
}
int
vprintf(const char *fmt, va_list ap)
{
int savintr;
struct putchar_arg pca;
int retval;
savintr = consintr; /* disable interrupts */
consintr = 0;
critical_enter();
pca.tty = NULL;
pca.flags = TOCONS | TOLOG;
pca.pri = -1;
pca.p_bufr = (char *) PCPU_PTR(cons_bufr);
pca.p_next = pca.p_bufr;
pca.n_bufr = PCPU_CONS_BUFR;
pca.remain = PCPU_CONS_BUFR;
*pca.p_next = '\0';
retval = kvprintf(fmt, putchar, &pca, 10, ap);
/* Write any buffered console output: */
if (*pca.p_bufr != '\0')
cnputs(pca.p_bufr);
if (!panicstr)
msgbuftrigger = 1;
consintr = savintr; /* reenable interrupts */
critical_exit();
return (retval);
}
static void
putcons(int c, struct putchar_arg *ap)
{
/* Check if no console output buffer was provided. */
if (ap->p_bufr == NULL)
/* Output direct to the console. */
cnputc(c);
else {
/* Buffer the character: */
if (c == '\n') {
*ap->p_next++ = '\r';
ap->remain--;
}
*ap->p_next++ = c;
ap->remain--;
/* Always leave the buffer zero terminated. */
*ap->p_next = '\0';
/* Check if the buffer needs to be flushed. */
if (ap->remain < 3 || c == '\n') {
cnputs(ap->p_bufr);
ap->p_next = ap->p_bufr;
ap->remain = ap->n_bufr;
*ap->p_next = '\0';
}
}
}
/*
* Print a character on console or users terminal. If destination is
* the console then the last bunch of characters are saved in msgbuf for
@ -331,17 +388,15 @@ putchar(int c, void *arg)
{
struct putchar_arg *ap = (struct putchar_arg*) arg;
struct tty *tp = ap->tty;
int consdirect, flags = ap->flags;
int flags = ap->flags;
consdirect = ((flags & TOCONS) && constty == NULL);
/* Don't use the tty code after a panic or while in ddb. */
if (panicstr)
consdirect = 1;
if (kdb_active)
consdirect = 1;
if (consdirect) {
if (kdb_active) {
if (c != '\0')
cnputc(c);
} else if (panicstr || ((flags & TOCONS) && constty == NULL)) {
if (c != '\0')
putcons(c, ap);
} else {
if ((flags & TOTTY) && tp != NULL)
tputchar(c, tp);
@ -349,7 +404,7 @@ putchar(int c, void *arg)
if (constty != NULL)
msgbuf_addchar(&consmsgbuf, c);
if (always_console_output && c != '\0')
cnputc(c);
putcons(c, ap);
}
}
if ((flags & TOLOG))

25
sys/kern/tty_cons.c
View File

@ -41,6 +41,8 @@ __FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/conf.h>
#include <sys/cons.h>
#include <sys/fcntl.h>
@ -117,6 +119,8 @@ 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 */
static struct mtx cnputs_mtx; /* Mutex for cnputs(). */
static int use_cnputs_mtx = 0; /* != 0 if cnputs_mtx locking reqd. */
static void constty_timeout(void *arg);
@ -639,6 +643,24 @@ cnputc(int c)
}
}
void
cnputs(char *p)
{
int c;
int unlock_reqd = 0;
if (use_cnputs_mtx) {
mtx_lock_spin(&cnputs_mtx);
unlock_reqd = 1;
}
while ((c = *p++) != '\0')
cnputc(c);
if (unlock_reqd)
mtx_unlock_spin(&cnputs_mtx);
}
static int consmsgbuf_size = 8192;
SYSCTL_INT(_kern, OID_AUTO, consmsgbuf_size, CTLFLAG_RW, &consmsgbuf_size, 0,
"");
@ -708,6 +730,9 @@ cn_drvinit(void *unused)
{
make_dev(&cn_cdevsw, 0, UID_ROOT, GID_WHEEL, 0600, "console");
mtx_init(&cnputs_mtx, "cnputs_mtx", NULL, MTX_SPIN | MTX_NOWITNESS);
use_cnputs_mtx = 1;
}
SYSINIT(cndev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, cn_drvinit, NULL)

1
sys/powerpc/powerpc/genassym.c
View File

@ -55,6 +55,7 @@
#include <machine/pmap.h>
#include <machine/sigframe.h>
ASSYM(PC_CONS_BUFR, offsetof(struct pcpu, pc_cons_bufr));
ASSYM(PC_CURTHREAD, offsetof(struct pcpu, pc_curthread));
ASSYM(PC_CURPCB, offsetof(struct pcpu, pc_curpcb));
ASSYM(PC_CURPMAP, offsetof(struct pcpu, pc_curpmap));

1
sys/sparc64/sparc64/genassym.c
View File

@ -198,6 +198,7 @@ ASSYM(HASH_ENTRY_SHIFT, HASH_ENTRY_SHIFT);
ASSYM(V_INTR, offsetof(struct vmmeter, v_intr));
ASSYM(PC_CONS_BUFR, offsetof(struct pcpu, pc_cons_bufr));
ASSYM(PC_CURTHREAD, offsetof(struct pcpu, pc_curthread));
ASSYM(PC_CURPCB, offsetof(struct pcpu, pc_curpcb));
ASSYM(PC_CPUID, offsetof(struct pcpu, pc_cpuid));

1
sys/sys/cons.h
View File

@ -106,6 +106,7 @@ void cnselect(struct consdev *);
int cncheckc(void);
int cngetc(void);
void cnputc(int);
void cnputs(char *);
int cnunavailable(void);
#endif /* _KERNEL */

5
sys/sys/pcpu.h
View File

@ -48,6 +48,9 @@
struct pcb;
struct thread;
/* Size of the per-cpu console buffer for printf(). */
#define PCPU_CONS_BUFR 128
/*
* This structure maps out the global data that needs to be kept on a
* per-cpu basis. The members are accessed via the PCPU_GET/SET/PTR
@ -71,6 +74,8 @@ struct pcpu {
int pc_ktr_idx; /* Index into trace table */
char *pc_ktr_buf;
#endif
char pc_cons_bufr[PCPU_CONS_BUFR];
/* Console buffer */
PCPU_MD_FIELDS;
struct vmmeter pc_cnt; /* VM stats counters */
struct device *pc_device;