[CPUFREQ] Recalibrate cpu_khz [2/2]
[linux-2.6/mini2440.git] / kernel / printk.c
blob01b58d7d17ff763d50f92cb80b66e8ffe67dad4f
1 /*
2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
11 * Ted Ts'o, 2/11/93.
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfreds@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton <andrewm@uow.edu.au>
19 #include <linux/kernel.h>
20 #include <linux/mm.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/smp_lock.h>
24 #include <linux/console.h>
25 #include <linux/init.h>
26 #include <linux/module.h>
27 #include <linux/interrupt.h> /* For in_interrupt() */
28 #include <linux/config.h>
29 #include <linux/delay.h>
30 #include <linux/smp.h>
31 #include <linux/security.h>
32 #include <linux/bootmem.h>
33 #include <linux/syscalls.h>
35 #include <asm/uaccess.h>
37 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
39 /* printk's without a loglevel use this.. */
40 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
42 /* We show everything that is MORE important than this.. */
43 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
44 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
46 DECLARE_WAIT_QUEUE_HEAD(log_wait);
48 int console_printk[4] = {
49 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
50 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
51 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
52 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
55 EXPORT_SYMBOL(console_printk);
58 * Low lever drivers may need that to know if they can schedule in
59 * their unblank() callback or not. So let's export it.
61 int oops_in_progress;
62 EXPORT_SYMBOL(oops_in_progress);
65 * console_sem protects the console_drivers list, and also
66 * provides serialisation for access to the entire console
67 * driver system.
69 static DECLARE_MUTEX(console_sem);
70 struct console *console_drivers;
72 * This is used for debugging the mess that is the VT code by
73 * keeping track if we have the console semaphore held. It's
74 * definitely not the perfect debug tool (we don't know if _WE_
75 * hold it are racing, but it helps tracking those weird code
76 * path in the console code where we end up in places I want
77 * locked without the console sempahore held
79 static int console_locked;
82 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
83 * It is also used in interesting ways to provide interlocking in
84 * release_console_sem().
86 static DEFINE_SPINLOCK(logbuf_lock);
88 #define LOG_BUF_MASK (log_buf_len-1)
89 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
92 * The indices into log_buf are not constrained to log_buf_len - they
93 * must be masked before subscripting
95 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
96 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
97 static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */
100 * Array of consoles built from command line options (console=)
102 struct console_cmdline
104 char name[8]; /* Name of the driver */
105 int index; /* Minor dev. to use */
106 char *options; /* Options for the driver */
109 #define MAX_CMDLINECONSOLES 8
111 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
112 static int selected_console = -1;
113 static int preferred_console = -1;
115 /* Flag: console code may call schedule() */
116 static int console_may_schedule;
118 #ifdef CONFIG_PRINTK
120 static char __log_buf[__LOG_BUF_LEN];
121 static char *log_buf = __log_buf;
122 static int log_buf_len = __LOG_BUF_LEN;
123 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
126 * Setup a list of consoles. Called from init/main.c
128 static int __init console_setup(char *str)
130 char name[sizeof(console_cmdline[0].name)];
131 char *s, *options;
132 int idx;
135 * Decode str into name, index, options.
137 if (str[0] >= '0' && str[0] <= '9') {
138 strcpy(name, "ttyS");
139 strncpy(name + 4, str, sizeof(name) - 5);
140 } else
141 strncpy(name, str, sizeof(name) - 1);
142 name[sizeof(name) - 1] = 0;
143 if ((options = strchr(str, ',')) != NULL)
144 *(options++) = 0;
145 #ifdef __sparc__
146 if (!strcmp(str, "ttya"))
147 strcpy(name, "ttyS0");
148 if (!strcmp(str, "ttyb"))
149 strcpy(name, "ttyS1");
150 #endif
151 for(s = name; *s; s++)
152 if ((*s >= '0' && *s <= '9') || *s == ',')
153 break;
154 idx = simple_strtoul(s, NULL, 10);
155 *s = 0;
157 add_preferred_console(name, idx, options);
158 return 1;
161 __setup("console=", console_setup);
163 static int __init log_buf_len_setup(char *str)
165 unsigned long size = memparse(str, &str);
166 unsigned long flags;
168 if (size)
169 size = roundup_pow_of_two(size);
170 if (size > log_buf_len) {
171 unsigned long start, dest_idx, offset;
172 char * new_log_buf;
174 new_log_buf = alloc_bootmem(size);
175 if (!new_log_buf) {
176 printk("log_buf_len: allocation failed\n");
177 goto out;
180 spin_lock_irqsave(&logbuf_lock, flags);
181 log_buf_len = size;
182 log_buf = new_log_buf;
184 offset = start = min(con_start, log_start);
185 dest_idx = 0;
186 while (start != log_end) {
187 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
188 start++;
189 dest_idx++;
191 log_start -= offset;
192 con_start -= offset;
193 log_end -= offset;
194 spin_unlock_irqrestore(&logbuf_lock, flags);
196 printk("log_buf_len: %d\n", log_buf_len);
198 out:
200 return 1;
203 __setup("log_buf_len=", log_buf_len_setup);
206 * Commands to do_syslog:
208 * 0 -- Close the log. Currently a NOP.
209 * 1 -- Open the log. Currently a NOP.
210 * 2 -- Read from the log.
211 * 3 -- Read all messages remaining in the ring buffer.
212 * 4 -- Read and clear all messages remaining in the ring buffer
213 * 5 -- Clear ring buffer.
214 * 6 -- Disable printk's to console
215 * 7 -- Enable printk's to console
216 * 8 -- Set level of messages printed to console
217 * 9 -- Return number of unread characters in the log buffer
218 * 10 -- Return size of the log buffer
220 int do_syslog(int type, char __user * buf, int len)
222 unsigned long i, j, limit, count;
223 int do_clear = 0;
224 char c;
225 int error = 0;
227 error = security_syslog(type);
228 if (error)
229 return error;
231 switch (type) {
232 case 0: /* Close log */
233 break;
234 case 1: /* Open log */
235 break;
236 case 2: /* Read from log */
237 error = -EINVAL;
238 if (!buf || len < 0)
239 goto out;
240 error = 0;
241 if (!len)
242 goto out;
243 if (!access_ok(VERIFY_WRITE, buf, len)) {
244 error = -EFAULT;
245 goto out;
247 error = wait_event_interruptible(log_wait, (log_start - log_end));
248 if (error)
249 goto out;
250 i = 0;
251 spin_lock_irq(&logbuf_lock);
252 while (!error && (log_start != log_end) && i < len) {
253 c = LOG_BUF(log_start);
254 log_start++;
255 spin_unlock_irq(&logbuf_lock);
256 error = __put_user(c,buf);
257 buf++;
258 i++;
259 cond_resched();
260 spin_lock_irq(&logbuf_lock);
262 spin_unlock_irq(&logbuf_lock);
263 if (!error)
264 error = i;
265 break;
266 case 4: /* Read/clear last kernel messages */
267 do_clear = 1;
268 /* FALL THRU */
269 case 3: /* Read last kernel messages */
270 error = -EINVAL;
271 if (!buf || len < 0)
272 goto out;
273 error = 0;
274 if (!len)
275 goto out;
276 if (!access_ok(VERIFY_WRITE, buf, len)) {
277 error = -EFAULT;
278 goto out;
280 count = len;
281 if (count > log_buf_len)
282 count = log_buf_len;
283 spin_lock_irq(&logbuf_lock);
284 if (count > logged_chars)
285 count = logged_chars;
286 if (do_clear)
287 logged_chars = 0;
288 limit = log_end;
290 * __put_user() could sleep, and while we sleep
291 * printk() could overwrite the messages
292 * we try to copy to user space. Therefore
293 * the messages are copied in reverse. <manfreds>
295 for(i = 0; i < count && !error; i++) {
296 j = limit-1-i;
297 if (j + log_buf_len < log_end)
298 break;
299 c = LOG_BUF(j);
300 spin_unlock_irq(&logbuf_lock);
301 error = __put_user(c,&buf[count-1-i]);
302 cond_resched();
303 spin_lock_irq(&logbuf_lock);
305 spin_unlock_irq(&logbuf_lock);
306 if (error)
307 break;
308 error = i;
309 if(i != count) {
310 int offset = count-error;
311 /* buffer overflow during copy, correct user buffer. */
312 for(i=0;i<error;i++) {
313 if (__get_user(c,&buf[i+offset]) ||
314 __put_user(c,&buf[i])) {
315 error = -EFAULT;
316 break;
318 cond_resched();
321 break;
322 case 5: /* Clear ring buffer */
323 logged_chars = 0;
324 break;
325 case 6: /* Disable logging to console */
326 console_loglevel = minimum_console_loglevel;
327 break;
328 case 7: /* Enable logging to console */
329 console_loglevel = default_console_loglevel;
330 break;
331 case 8: /* Set level of messages printed to console */
332 error = -EINVAL;
333 if (len < 1 || len > 8)
334 goto out;
335 if (len < minimum_console_loglevel)
336 len = minimum_console_loglevel;
337 console_loglevel = len;
338 error = 0;
339 break;
340 case 9: /* Number of chars in the log buffer */
341 error = log_end - log_start;
342 break;
343 case 10: /* Size of the log buffer */
344 error = log_buf_len;
345 break;
346 default:
347 error = -EINVAL;
348 break;
350 out:
351 return error;
354 asmlinkage long sys_syslog(int type, char __user * buf, int len)
356 return do_syslog(type, buf, len);
360 * Call the console drivers on a range of log_buf
362 static void __call_console_drivers(unsigned long start, unsigned long end)
364 struct console *con;
366 for (con = console_drivers; con; con = con->next) {
367 if ((con->flags & CON_ENABLED) && con->write)
368 con->write(con, &LOG_BUF(start), end - start);
373 * Write out chars from start to end - 1 inclusive
375 static void _call_console_drivers(unsigned long start,
376 unsigned long end, int msg_log_level)
378 if (msg_log_level < console_loglevel &&
379 console_drivers && start != end) {
380 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
381 /* wrapped write */
382 __call_console_drivers(start & LOG_BUF_MASK,
383 log_buf_len);
384 __call_console_drivers(0, end & LOG_BUF_MASK);
385 } else {
386 __call_console_drivers(start, end);
392 * Call the console drivers, asking them to write out
393 * log_buf[start] to log_buf[end - 1].
394 * The console_sem must be held.
396 static void call_console_drivers(unsigned long start, unsigned long end)
398 unsigned long cur_index, start_print;
399 static int msg_level = -1;
401 if (((long)(start - end)) > 0)
402 BUG();
404 cur_index = start;
405 start_print = start;
406 while (cur_index != end) {
407 if ( msg_level < 0 &&
408 ((end - cur_index) > 2) &&
409 LOG_BUF(cur_index + 0) == '<' &&
410 LOG_BUF(cur_index + 1) >= '0' &&
411 LOG_BUF(cur_index + 1) <= '7' &&
412 LOG_BUF(cur_index + 2) == '>')
414 msg_level = LOG_BUF(cur_index + 1) - '0';
415 cur_index += 3;
416 start_print = cur_index;
418 while (cur_index != end) {
419 char c = LOG_BUF(cur_index);
420 cur_index++;
422 if (c == '\n') {
423 if (msg_level < 0) {
425 * printk() has already given us loglevel tags in
426 * the buffer. This code is here in case the
427 * log buffer has wrapped right round and scribbled
428 * on those tags
430 msg_level = default_message_loglevel;
432 _call_console_drivers(start_print, cur_index, msg_level);
433 msg_level = -1;
434 start_print = cur_index;
435 break;
439 _call_console_drivers(start_print, end, msg_level);
442 static void emit_log_char(char c)
444 LOG_BUF(log_end) = c;
445 log_end++;
446 if (log_end - log_start > log_buf_len)
447 log_start = log_end - log_buf_len;
448 if (log_end - con_start > log_buf_len)
449 con_start = log_end - log_buf_len;
450 if (logged_chars < log_buf_len)
451 logged_chars++;
455 * Zap console related locks when oopsing. Only zap at most once
456 * every 10 seconds, to leave time for slow consoles to print a
457 * full oops.
459 static void zap_locks(void)
461 static unsigned long oops_timestamp;
463 if (time_after_eq(jiffies, oops_timestamp) &&
464 !time_after(jiffies, oops_timestamp + 30*HZ))
465 return;
467 oops_timestamp = jiffies;
469 /* If a crash is occurring, make sure we can't deadlock */
470 spin_lock_init(&logbuf_lock);
471 /* And make sure that we print immediately */
472 init_MUTEX(&console_sem);
475 #if defined(CONFIG_PRINTK_TIME)
476 static int printk_time = 1;
477 #else
478 static int printk_time = 0;
479 #endif
481 static int __init printk_time_setup(char *str)
483 if (*str)
484 return 0;
485 printk_time = 1;
486 return 1;
489 __setup("time", printk_time_setup);
492 * This is printk. It can be called from any context. We want it to work.
494 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
495 * call the console drivers. If we fail to get the semaphore we place the output
496 * into the log buffer and return. The current holder of the console_sem will
497 * notice the new output in release_console_sem() and will send it to the
498 * consoles before releasing the semaphore.
500 * One effect of this deferred printing is that code which calls printk() and
501 * then changes console_loglevel may break. This is because console_loglevel
502 * is inspected when the actual printing occurs.
505 asmlinkage int printk(const char *fmt, ...)
507 va_list args;
508 int r;
510 va_start(args, fmt);
511 r = vprintk(fmt, args);
512 va_end(args);
514 return r;
517 asmlinkage int vprintk(const char *fmt, va_list args)
519 unsigned long flags;
520 int printed_len;
521 char *p;
522 static char printk_buf[1024];
523 static int log_level_unknown = 1;
525 if (unlikely(oops_in_progress))
526 zap_locks();
528 /* This stops the holder of console_sem just where we want him */
529 spin_lock_irqsave(&logbuf_lock, flags);
531 /* Emit the output into the temporary buffer */
532 printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
535 * Copy the output into log_buf. If the caller didn't provide
536 * appropriate log level tags, we insert them here
538 for (p = printk_buf; *p; p++) {
539 if (log_level_unknown) {
540 /* log_level_unknown signals the start of a new line */
541 if (printk_time) {
542 int loglev_char;
543 char tbuf[50], *tp;
544 unsigned tlen;
545 unsigned long long t;
546 unsigned long nanosec_rem;
549 * force the log level token to be
550 * before the time output.
552 if (p[0] == '<' && p[1] >='0' &&
553 p[1] <= '7' && p[2] == '>') {
554 loglev_char = p[1];
555 p += 3;
556 printed_len += 3;
557 } else {
558 loglev_char = default_message_loglevel
559 + '0';
561 t = sched_clock();
562 nanosec_rem = do_div(t, 1000000000);
563 tlen = sprintf(tbuf,
564 "<%c>[%5lu.%06lu] ",
565 loglev_char,
566 (unsigned long)t,
567 nanosec_rem/1000);
569 for (tp = tbuf; tp < tbuf + tlen; tp++)
570 emit_log_char(*tp);
571 printed_len += tlen - 3;
572 } else {
573 if (p[0] != '<' || p[1] < '0' ||
574 p[1] > '7' || p[2] != '>') {
575 emit_log_char('<');
576 emit_log_char(default_message_loglevel
577 + '0');
578 emit_log_char('>');
580 printed_len += 3;
582 log_level_unknown = 0;
583 if (!*p)
584 break;
586 emit_log_char(*p);
587 if (*p == '\n')
588 log_level_unknown = 1;
591 if (!cpu_online(smp_processor_id()) &&
592 system_state != SYSTEM_RUNNING) {
594 * Some console drivers may assume that per-cpu resources have
595 * been allocated. So don't allow them to be called by this
596 * CPU until it is officially up. We shouldn't be calling into
597 * random console drivers on a CPU which doesn't exist yet..
599 spin_unlock_irqrestore(&logbuf_lock, flags);
600 goto out;
602 if (!down_trylock(&console_sem)) {
603 console_locked = 1;
605 * We own the drivers. We can drop the spinlock and let
606 * release_console_sem() print the text
608 spin_unlock_irqrestore(&logbuf_lock, flags);
609 console_may_schedule = 0;
610 release_console_sem();
611 } else {
613 * Someone else owns the drivers. We drop the spinlock, which
614 * allows the semaphore holder to proceed and to call the
615 * console drivers with the output which we just produced.
617 spin_unlock_irqrestore(&logbuf_lock, flags);
619 out:
620 return printed_len;
622 EXPORT_SYMBOL(printk);
623 EXPORT_SYMBOL(vprintk);
625 #else
627 asmlinkage long sys_syslog(int type, char __user * buf, int len)
629 return 0;
632 int do_syslog(int type, char __user * buf, int len) { return 0; }
633 static void call_console_drivers(unsigned long start, unsigned long end) {}
635 #endif
638 * add_preferred_console - add a device to the list of preferred consoles.
640 * The last preferred console added will be used for kernel messages
641 * and stdin/out/err for init. Normally this is used by console_setup
642 * above to handle user-supplied console arguments; however it can also
643 * be used by arch-specific code either to override the user or more
644 * commonly to provide a default console (ie from PROM variables) when
645 * the user has not supplied one.
647 int __init add_preferred_console(char *name, int idx, char *options)
649 struct console_cmdline *c;
650 int i;
653 * See if this tty is not yet registered, and
654 * if we have a slot free.
656 for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
657 if (strcmp(console_cmdline[i].name, name) == 0 &&
658 console_cmdline[i].index == idx) {
659 selected_console = i;
660 return 0;
662 if (i == MAX_CMDLINECONSOLES)
663 return -E2BIG;
664 selected_console = i;
665 c = &console_cmdline[i];
666 memcpy(c->name, name, sizeof(c->name));
667 c->name[sizeof(c->name) - 1] = 0;
668 c->options = options;
669 c->index = idx;
670 return 0;
674 * acquire_console_sem - lock the console system for exclusive use.
676 * Acquires a semaphore which guarantees that the caller has
677 * exclusive access to the console system and the console_drivers list.
679 * Can sleep, returns nothing.
681 void acquire_console_sem(void)
683 if (in_interrupt())
684 BUG();
685 down(&console_sem);
686 console_locked = 1;
687 console_may_schedule = 1;
689 EXPORT_SYMBOL(acquire_console_sem);
691 int try_acquire_console_sem(void)
693 if (down_trylock(&console_sem))
694 return -1;
695 console_locked = 1;
696 console_may_schedule = 0;
697 return 0;
699 EXPORT_SYMBOL(try_acquire_console_sem);
701 int is_console_locked(void)
703 return console_locked;
705 EXPORT_SYMBOL(is_console_locked);
708 * release_console_sem - unlock the console system
710 * Releases the semaphore which the caller holds on the console system
711 * and the console driver list.
713 * While the semaphore was held, console output may have been buffered
714 * by printk(). If this is the case, release_console_sem() emits
715 * the output prior to releasing the semaphore.
717 * If there is output waiting for klogd, we wake it up.
719 * release_console_sem() may be called from any context.
721 void release_console_sem(void)
723 unsigned long flags;
724 unsigned long _con_start, _log_end;
725 unsigned long wake_klogd = 0;
727 for ( ; ; ) {
728 spin_lock_irqsave(&logbuf_lock, flags);
729 wake_klogd |= log_start - log_end;
730 if (con_start == log_end)
731 break; /* Nothing to print */
732 _con_start = con_start;
733 _log_end = log_end;
734 con_start = log_end; /* Flush */
735 spin_unlock(&logbuf_lock);
736 call_console_drivers(_con_start, _log_end);
737 local_irq_restore(flags);
739 console_locked = 0;
740 console_may_schedule = 0;
741 up(&console_sem);
742 spin_unlock_irqrestore(&logbuf_lock, flags);
743 if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
744 wake_up_interruptible(&log_wait);
746 EXPORT_SYMBOL(release_console_sem);
748 /** console_conditional_schedule - yield the CPU if required
750 * If the console code is currently allowed to sleep, and
751 * if this CPU should yield the CPU to another task, do
752 * so here.
754 * Must be called within acquire_console_sem().
756 void __sched console_conditional_schedule(void)
758 if (console_may_schedule)
759 cond_resched();
761 EXPORT_SYMBOL(console_conditional_schedule);
763 void console_print(const char *s)
765 printk(KERN_EMERG "%s", s);
767 EXPORT_SYMBOL(console_print);
769 void console_unblank(void)
771 struct console *c;
774 * console_unblank can no longer be called in interrupt context unless
775 * oops_in_progress is set to 1..
777 if (oops_in_progress) {
778 if (down_trylock(&console_sem) != 0)
779 return;
780 } else
781 acquire_console_sem();
783 console_locked = 1;
784 console_may_schedule = 0;
785 for (c = console_drivers; c != NULL; c = c->next)
786 if ((c->flags & CON_ENABLED) && c->unblank)
787 c->unblank();
788 release_console_sem();
790 EXPORT_SYMBOL(console_unblank);
793 * Return the console tty driver structure and its associated index
795 struct tty_driver *console_device(int *index)
797 struct console *c;
798 struct tty_driver *driver = NULL;
800 acquire_console_sem();
801 for (c = console_drivers; c != NULL; c = c->next) {
802 if (!c->device)
803 continue;
804 driver = c->device(c, index);
805 if (driver)
806 break;
808 release_console_sem();
809 return driver;
813 * Prevent further output on the passed console device so that (for example)
814 * serial drivers can disable console output before suspending a port, and can
815 * re-enable output afterwards.
817 void console_stop(struct console *console)
819 acquire_console_sem();
820 console->flags &= ~CON_ENABLED;
821 release_console_sem();
823 EXPORT_SYMBOL(console_stop);
825 void console_start(struct console *console)
827 acquire_console_sem();
828 console->flags |= CON_ENABLED;
829 release_console_sem();
831 EXPORT_SYMBOL(console_start);
834 * The console driver calls this routine during kernel initialization
835 * to register the console printing procedure with printk() and to
836 * print any messages that were printed by the kernel before the
837 * console driver was initialized.
839 void register_console(struct console * console)
841 int i;
842 unsigned long flags;
844 if (preferred_console < 0)
845 preferred_console = selected_console;
848 * See if we want to use this console driver. If we
849 * didn't select a console we take the first one
850 * that registers here.
852 if (preferred_console < 0) {
853 if (console->index < 0)
854 console->index = 0;
855 if (console->setup == NULL ||
856 console->setup(console, NULL) == 0) {
857 console->flags |= CON_ENABLED | CON_CONSDEV;
858 preferred_console = 0;
863 * See if this console matches one we selected on
864 * the command line.
866 for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) {
867 if (strcmp(console_cmdline[i].name, console->name) != 0)
868 continue;
869 if (console->index >= 0 &&
870 console->index != console_cmdline[i].index)
871 continue;
872 if (console->index < 0)
873 console->index = console_cmdline[i].index;
874 if (console->setup &&
875 console->setup(console, console_cmdline[i].options) != 0)
876 break;
877 console->flags |= CON_ENABLED;
878 console->index = console_cmdline[i].index;
879 if (i == preferred_console)
880 console->flags |= CON_CONSDEV;
881 break;
884 if (!(console->flags & CON_ENABLED))
885 return;
887 if (console_drivers && (console_drivers->flags & CON_BOOT)) {
888 unregister_console(console_drivers);
889 console->flags &= ~CON_PRINTBUFFER;
893 * Put this console in the list - keep the
894 * preferred driver at the head of the list.
896 acquire_console_sem();
897 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
898 console->next = console_drivers;
899 console_drivers = console;
900 } else {
901 console->next = console_drivers->next;
902 console_drivers->next = console;
904 if (console->flags & CON_PRINTBUFFER) {
906 * release_console_sem() will print out the buffered messages
907 * for us.
909 spin_lock_irqsave(&logbuf_lock, flags);
910 con_start = log_start;
911 spin_unlock_irqrestore(&logbuf_lock, flags);
913 release_console_sem();
915 EXPORT_SYMBOL(register_console);
917 int unregister_console(struct console * console)
919 struct console *a,*b;
920 int res = 1;
922 acquire_console_sem();
923 if (console_drivers == console) {
924 console_drivers=console->next;
925 res = 0;
926 } else {
927 for (a=console_drivers->next, b=console_drivers ;
928 a; b=a, a=b->next) {
929 if (a == console) {
930 b->next = a->next;
931 res = 0;
932 break;
937 /* If last console is removed, we re-enable picking the first
938 * one that gets registered. Without that, pmac early boot console
939 * would prevent fbcon from taking over.
941 if (console_drivers == NULL)
942 preferred_console = selected_console;
945 release_console_sem();
946 return res;
948 EXPORT_SYMBOL(unregister_console);
951 * tty_write_message - write a message to a certain tty, not just the console.
953 * This is used for messages that need to be redirected to a specific tty.
954 * We don't put it into the syslog queue right now maybe in the future if
955 * really needed.
957 void tty_write_message(struct tty_struct *tty, char *msg)
959 if (tty && tty->driver->write)
960 tty->driver->write(tty, msg, strlen(msg));
961 return;
965 * printk rate limiting, lifted from the networking subsystem.
967 * This enforces a rate limit: not more than one kernel message
968 * every printk_ratelimit_jiffies to make a denial-of-service
969 * attack impossible.
971 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
973 static DEFINE_SPINLOCK(ratelimit_lock);
974 static unsigned long toks = 10*5*HZ;
975 static unsigned long last_msg;
976 static int missed;
977 unsigned long flags;
978 unsigned long now = jiffies;
980 spin_lock_irqsave(&ratelimit_lock, flags);
981 toks += now - last_msg;
982 last_msg = now;
983 if (toks > (ratelimit_burst * ratelimit_jiffies))
984 toks = ratelimit_burst * ratelimit_jiffies;
985 if (toks >= ratelimit_jiffies) {
986 int lost = missed;
987 missed = 0;
988 toks -= ratelimit_jiffies;
989 spin_unlock_irqrestore(&ratelimit_lock, flags);
990 if (lost)
991 printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
992 return 1;
994 missed++;
995 spin_unlock_irqrestore(&ratelimit_lock, flags);
996 return 0;
998 EXPORT_SYMBOL(__printk_ratelimit);
1000 /* minimum time in jiffies between messages */
1001 int printk_ratelimit_jiffies = 5*HZ;
1003 /* number of messages we send before ratelimiting */
1004 int printk_ratelimit_burst = 10;
1006 int printk_ratelimit(void)
1008 return __printk_ratelimit(printk_ratelimit_jiffies,
1009 printk_ratelimit_burst);
1011 EXPORT_SYMBOL(printk_ratelimit);