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).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton <andrewm@uow.edu.au>
19 #include <linux/kernel.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/jiffies.h>
27 #include <linux/nmi.h>
28 #include <linux/module.h>
29 #include <linux/moduleparam.h>
30 #include <linux/interrupt.h> /* For in_interrupt() */
31 #include <linux/delay.h>
32 #include <linux/smp.h>
33 #include <linux/security.h>
34 #include <linux/bootmem.h>
35 #include <linux/syscalls.h>
36 #include <linux/vserver/cvirt.h>
38 #include <asm/uaccess.h>
40 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
42 /* printk's without a loglevel use this.. */
43 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
45 /* We show everything that is MORE important than this.. */
46 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
47 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
49 DECLARE_WAIT_QUEUE_HEAD(log_wait);
51 int console_printk[4] = {
52 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
53 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
54 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
55 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
58 EXPORT_UNUSED_SYMBOL(console_printk); /* June 2006 */
61 * Low lever drivers may need that to know if they can schedule in
62 * their unblank() callback or not. So let's export it.
65 EXPORT_SYMBOL(oops_in_progress);
68 * console_sem protects the console_drivers list, and also
69 * provides serialisation for access to the entire console
72 static DECLARE_MUTEX(console_sem);
73 static DECLARE_MUTEX(secondary_console_sem);
74 struct console *console_drivers;
76 * This is used for debugging the mess that is the VT code by
77 * keeping track if we have the console semaphore held. It's
78 * definitely not the perfect debug tool (we don't know if _WE_
79 * hold it are racing, but it helps tracking those weird code
80 * path in the console code where we end up in places I want
81 * locked without the console sempahore held
83 static int console_locked, console_suspended;
86 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
87 * It is also used in interesting ways to provide interlocking in
88 * release_console_sem().
90 static DEFINE_SPINLOCK(logbuf_lock);
92 #define LOG_BUF_MASK (log_buf_len-1)
93 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
96 * The indices into log_buf are not constrained to log_buf_len - they
97 * must be masked before subscripting
99 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
100 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
101 static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */
104 * Array of consoles built from command line options (console=)
106 struct console_cmdline
108 char name[8]; /* Name of the driver */
109 int index; /* Minor dev. to use */
110 char *options; /* Options for the driver */
113 #define MAX_CMDLINECONSOLES 8
115 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
116 static int selected_console = -1;
117 static int preferred_console = -1;
119 /* Flag: console code may call schedule() */
120 static int console_may_schedule;
124 static char __log_buf[__LOG_BUF_LEN];
125 static char *log_buf = __log_buf;
126 static int log_buf_len = __LOG_BUF_LEN;
127 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
129 static int __init log_buf_len_setup(char *str)
131 unsigned long size = memparse(str, &str);
135 size = roundup_pow_of_two(size);
136 if (size > log_buf_len) {
137 unsigned long start, dest_idx, offset;
140 new_log_buf = alloc_bootmem(size);
142 printk(KERN_WARNING "log_buf_len: allocation failed\n");
146 spin_lock_irqsave(&logbuf_lock, flags);
148 log_buf = new_log_buf;
150 offset = start = min(con_start, log_start);
152 while (start != log_end) {
153 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
160 spin_unlock_irqrestore(&logbuf_lock, flags);
162 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
168 __setup("log_buf_len=", log_buf_len_setup);
170 #ifdef CONFIG_BOOT_DELAY
172 extern unsigned int boot_delay; /* msecs to delay after each printk during bootup */
173 extern long preset_lpj;
174 extern unsigned long long printk_delay_msec;
176 static void boot_delay_msec(int millisecs)
178 unsigned long long k = printk_delay_msec * millisecs;
179 unsigned long timeout;
181 timeout = jiffies + msecs_to_jiffies(millisecs);
186 * use (volatile) jiffies to prevent
187 * compiler reduction; loop termination via jiffies
188 * is secondary and may or may not happen.
190 if (time_after(jiffies, timeout))
192 touch_nmi_watchdog();
199 * Commands to do_syslog:
201 * 0 -- Close the log. Currently a NOP.
202 * 1 -- Open the log. Currently a NOP.
203 * 2 -- Read from the log.
204 * 3 -- Read all messages remaining in the ring buffer.
205 * 4 -- Read and clear all messages remaining in the ring buffer
206 * 5 -- Clear ring buffer.
207 * 6 -- Disable printk's to console
208 * 7 -- Enable printk's to console
209 * 8 -- Set level of messages printed to console
210 * 9 -- Return number of unread characters in the log buffer
211 * 10 -- Return size of the log buffer
213 int do_syslog(int type, char __user *buf, int len)
215 unsigned long i, j, limit, count;
220 error = security_syslog(type);
224 if ((type >= 2) && (type <= 4)) {
231 if (!access_ok(VERIFY_WRITE, buf, len)) {
236 if (!vx_check(0, VX_ADMIN|VX_WATCH))
237 return vx_do_syslog(type, buf, len);
240 case 0: /* Close log */
242 case 1: /* Open log */
244 case 2: /* Read from log */
245 error = wait_event_interruptible(log_wait,
246 (log_start - log_end));
250 spin_lock_irq(&logbuf_lock);
251 while (!error && (log_start != log_end) && i < len) {
252 c = LOG_BUF(log_start);
254 spin_unlock_irq(&logbuf_lock);
255 error = __put_user(c,buf);
259 spin_lock_irq(&logbuf_lock);
261 spin_unlock_irq(&logbuf_lock);
265 case 4: /* Read/clear last kernel messages */
268 case 3: /* Read last kernel messages */
270 if (count > log_buf_len)
272 spin_lock_irq(&logbuf_lock);
273 if (count > logged_chars)
274 count = logged_chars;
279 * __put_user() could sleep, and while we sleep
280 * printk() could overwrite the messages
281 * we try to copy to user space. Therefore
282 * the messages are copied in reverse. <manfreds>
284 for (i = 0; i < count && !error; i++) {
286 if (j + log_buf_len < log_end)
289 spin_unlock_irq(&logbuf_lock);
290 error = __put_user(c,&buf[count-1-i]);
292 spin_lock_irq(&logbuf_lock);
294 spin_unlock_irq(&logbuf_lock);
299 int offset = count-error;
300 /* buffer overflow during copy, correct user buffer. */
301 for (i = 0; i < error; i++) {
302 if (__get_user(c,&buf[i+offset]) ||
303 __put_user(c,&buf[i])) {
311 case 5: /* Clear ring buffer */
314 case 6: /* Disable logging to console */
315 console_loglevel = minimum_console_loglevel;
317 case 7: /* Enable logging to console */
318 console_loglevel = default_console_loglevel;
320 case 8: /* Set level of messages printed to console */
322 if (len < 1 || len > 8)
324 if (len < minimum_console_loglevel)
325 len = minimum_console_loglevel;
326 console_loglevel = len;
329 case 9: /* Number of chars in the log buffer */
330 error = log_end - log_start;
332 case 10: /* Size of the log buffer */
343 asmlinkage long sys_syslog(int type, char __user *buf, int len)
345 return do_syslog(type, buf, len);
349 * Call the console drivers on a range of log_buf
351 static void __call_console_drivers(unsigned long start, unsigned long end)
355 for (con = console_drivers; con; con = con->next) {
356 if ((con->flags & CON_ENABLED) && con->write &&
357 (cpu_online(smp_processor_id()) ||
358 (con->flags & CON_ANYTIME)))
359 con->write(con, &LOG_BUF(start), end - start);
364 * Write out chars from start to end - 1 inclusive
366 static void _call_console_drivers(unsigned long start,
367 unsigned long end, int msg_log_level)
369 if (msg_log_level < console_loglevel &&
370 console_drivers && start != end) {
371 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
373 __call_console_drivers(start & LOG_BUF_MASK,
375 __call_console_drivers(0, end & LOG_BUF_MASK);
377 __call_console_drivers(start, end);
383 * Call the console drivers, asking them to write out
384 * log_buf[start] to log_buf[end - 1].
385 * The console_sem must be held.
387 static void call_console_drivers(unsigned long start, unsigned long end)
389 unsigned long cur_index, start_print;
390 static int msg_level = -1;
392 BUG_ON(((long)(start - end)) > 0);
396 while (cur_index != end) {
397 if (msg_level < 0 && ((end - cur_index) > 2) &&
398 LOG_BUF(cur_index + 0) == '<' &&
399 LOG_BUF(cur_index + 1) >= '0' &&
400 LOG_BUF(cur_index + 1) <= '7' &&
401 LOG_BUF(cur_index + 2) == '>') {
402 msg_level = LOG_BUF(cur_index + 1) - '0';
404 start_print = cur_index;
406 while (cur_index != end) {
407 char c = LOG_BUF(cur_index);
413 * printk() has already given us loglevel tags in
414 * the buffer. This code is here in case the
415 * log buffer has wrapped right round and scribbled
418 msg_level = default_message_loglevel;
420 _call_console_drivers(start_print, cur_index, msg_level);
422 start_print = cur_index;
427 _call_console_drivers(start_print, end, msg_level);
430 static void emit_log_char(char c)
432 LOG_BUF(log_end) = c;
434 if (log_end - log_start > log_buf_len)
435 log_start = log_end - log_buf_len;
436 if (log_end - con_start > log_buf_len)
437 con_start = log_end - log_buf_len;
438 if (logged_chars < log_buf_len)
443 * Zap console related locks when oopsing. Only zap at most once
444 * every 10 seconds, to leave time for slow consoles to print a
447 static void zap_locks(void)
449 static unsigned long oops_timestamp;
451 if (time_after_eq(jiffies, oops_timestamp) &&
452 !time_after(jiffies, oops_timestamp + 30 * HZ))
455 oops_timestamp = jiffies;
457 /* If a crash is occurring, make sure we can't deadlock */
458 spin_lock_init(&logbuf_lock);
459 /* And make sure that we print immediately */
460 init_MUTEX(&console_sem);
463 #if defined(CONFIG_PRINTK_TIME)
464 static int printk_time = 1;
466 static int printk_time = 0;
468 module_param(printk_time, int, S_IRUGO | S_IWUSR);
470 static int __init printk_time_setup(char *str)
478 __setup("time", printk_time_setup);
480 __attribute__((weak)) unsigned long long printk_clock(void)
482 return sched_clock();
485 /* Check if we have any console registered that can be called early in boot. */
486 static int have_callable_console(void)
490 for (con = console_drivers; con; con = con->next)
491 if (con->flags & CON_ANYTIME)
498 * printk - print a kernel message
499 * @fmt: format string
501 * This is printk. It can be called from any context. We want it to work.
503 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
504 * call the console drivers. If we fail to get the semaphore we place the output
505 * into the log buffer and return. The current holder of the console_sem will
506 * notice the new output in release_console_sem() and will send it to the
507 * consoles before releasing the semaphore.
509 * One effect of this deferred printing is that code which calls printk() and
510 * then changes console_loglevel may break. This is because console_loglevel
511 * is inspected when the actual printing occurs.
517 asmlinkage int printk(const char *fmt, ...)
523 r = vprintk(fmt, args);
526 #ifdef CONFIG_BOOT_DELAY
527 if (boot_delay && system_state == SYSTEM_BOOTING)
528 boot_delay_msec(boot_delay);
534 /* cpu currently holding logbuf_lock */
535 static volatile unsigned int printk_cpu = UINT_MAX;
537 asmlinkage int vprintk(const char *fmt, va_list args)
542 static char printk_buf[1024];
543 static int log_level_unknown = 1;
546 if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
547 /* If a crash is occurring during printk() on this CPU,
548 * make sure we can't deadlock */
551 /* This stops the holder of console_sem just where we want him */
552 local_irq_save(flags);
554 spin_lock(&logbuf_lock);
555 printk_cpu = smp_processor_id();
557 /* Emit the output into the temporary buffer */
558 printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
561 * Copy the output into log_buf. If the caller didn't provide
562 * appropriate log level tags, we insert them here
564 for (p = printk_buf; *p; p++) {
565 if (log_level_unknown) {
566 /* log_level_unknown signals the start of a new line */
571 unsigned long long t;
572 unsigned long nanosec_rem;
575 * force the log level token to be
576 * before the time output.
578 if (p[0] == '<' && p[1] >='0' &&
579 p[1] <= '7' && p[2] == '>') {
584 loglev_char = default_message_loglevel
588 nanosec_rem = do_div(t, 1000000000);
595 for (tp = tbuf; tp < tbuf + tlen; tp++)
599 if (p[0] != '<' || p[1] < '0' ||
600 p[1] > '7' || p[2] != '>') {
602 emit_log_char(default_message_loglevel
608 log_level_unknown = 0;
614 log_level_unknown = 1;
617 if (!down_trylock(&console_sem)) {
619 * We own the drivers. We can drop the spinlock and
620 * let release_console_sem() print the text, maybe ...
623 printk_cpu = UINT_MAX;
624 spin_unlock(&logbuf_lock);
627 * Console drivers may assume that per-cpu resources have
628 * been allocated. So unless they're explicitly marked as
629 * being able to cope (CON_ANYTIME) don't call them until
630 * this CPU is officially up.
632 if (cpu_online(smp_processor_id()) || have_callable_console()) {
633 console_may_schedule = 0;
634 release_console_sem();
636 /* Release by hand to avoid flushing the buffer. */
641 local_irq_restore(flags);
644 * Someone else owns the drivers. We drop the spinlock, which
645 * allows the semaphore holder to proceed and to call the
646 * console drivers with the output which we just produced.
648 printk_cpu = UINT_MAX;
649 spin_unlock(&logbuf_lock);
651 local_irq_restore(flags);
657 EXPORT_SYMBOL(printk);
658 EXPORT_SYMBOL(vprintk);
662 asmlinkage long sys_syslog(int type, char __user *buf, int len)
667 int do_syslog(int type, char __user *buf, int len)
672 static void call_console_drivers(unsigned long start, unsigned long end)
679 * Set up a list of consoles. Called from init/main.c
681 static int __init console_setup(char *str)
683 char name[sizeof(console_cmdline[0].name)];
688 * Decode str into name, index, options.
690 if (str[0] >= '0' && str[0] <= '9') {
691 strcpy(name, "ttyS");
692 strncpy(name + 4, str, sizeof(name) - 5);
694 strncpy(name, str, sizeof(name) - 1);
696 name[sizeof(name) - 1] = 0;
697 if ((options = strchr(str, ',')) != NULL)
700 if (!strcmp(str, "ttya"))
701 strcpy(name, "ttyS0");
702 if (!strcmp(str, "ttyb"))
703 strcpy(name, "ttyS1");
705 for (s = name; *s; s++)
706 if ((*s >= '0' && *s <= '9') || *s == ',')
708 idx = simple_strtoul(s, NULL, 10);
711 add_preferred_console(name, idx, options);
714 __setup("console=", console_setup);
717 * add_preferred_console - add a device to the list of preferred consoles.
720 * @options: options for this console
722 * The last preferred console added will be used for kernel messages
723 * and stdin/out/err for init. Normally this is used by console_setup
724 * above to handle user-supplied console arguments; however it can also
725 * be used by arch-specific code either to override the user or more
726 * commonly to provide a default console (ie from PROM variables) when
727 * the user has not supplied one.
729 int __init add_preferred_console(char *name, int idx, char *options)
731 struct console_cmdline *c;
735 * See if this tty is not yet registered, and
736 * if we have a slot free.
738 for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
739 if (strcmp(console_cmdline[i].name, name) == 0 &&
740 console_cmdline[i].index == idx) {
741 selected_console = i;
744 if (i == MAX_CMDLINECONSOLES)
746 selected_console = i;
747 c = &console_cmdline[i];
748 memcpy(c->name, name, sizeof(c->name));
749 c->name[sizeof(c->name) - 1] = 0;
750 c->options = options;
756 * suspend_console - suspend the console subsystem
758 * This disables printk() while we go into suspend states
760 void suspend_console(void)
762 acquire_console_sem();
763 console_suspended = 1;
766 void resume_console(void)
768 console_suspended = 0;
769 release_console_sem();
773 * acquire_console_sem - lock the console system for exclusive use.
775 * Acquires a semaphore which guarantees that the caller has
776 * exclusive access to the console system and the console_drivers list.
778 * Can sleep, returns nothing.
780 void acquire_console_sem(void)
782 BUG_ON(in_interrupt());
783 if (console_suspended) {
784 down(&secondary_console_sem);
789 console_may_schedule = 1;
791 EXPORT_SYMBOL(acquire_console_sem);
793 int try_acquire_console_sem(void)
795 if (down_trylock(&console_sem))
798 console_may_schedule = 0;
801 EXPORT_SYMBOL(try_acquire_console_sem);
803 int is_console_locked(void)
805 return console_locked;
807 EXPORT_UNUSED_SYMBOL(is_console_locked); /* June 2006 */
810 * release_console_sem - unlock the console system
812 * Releases the semaphore which the caller holds on the console system
813 * and the console driver list.
815 * While the semaphore was held, console output may have been buffered
816 * by printk(). If this is the case, release_console_sem() emits
817 * the output prior to releasing the semaphore.
819 * If there is output waiting for klogd, we wake it up.
821 * release_console_sem() may be called from any context.
823 void release_console_sem(void)
826 unsigned long _con_start, _log_end;
827 unsigned long wake_klogd = 0;
829 if (console_suspended) {
830 up(&secondary_console_sem);
834 console_may_schedule = 0;
837 spin_lock_irqsave(&logbuf_lock, flags);
838 wake_klogd |= log_start - log_end;
839 if (con_start == log_end)
840 break; /* Nothing to print */
841 _con_start = con_start;
843 con_start = log_end; /* Flush */
844 spin_unlock(&logbuf_lock);
845 call_console_drivers(_con_start, _log_end);
846 local_irq_restore(flags);
850 spin_unlock_irqrestore(&logbuf_lock, flags);
851 if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) {
853 * If we printk from within the lock dependency code,
854 * from within the scheduler code, then do not lock
855 * up due to self-recursion:
857 if (!lockdep_internal())
858 wake_up_interruptible(&log_wait);
861 EXPORT_SYMBOL(release_console_sem);
864 * console_conditional_schedule - yield the CPU if required
866 * If the console code is currently allowed to sleep, and
867 * if this CPU should yield the CPU to another task, do
870 * Must be called within acquire_console_sem().
872 void __sched console_conditional_schedule(void)
874 if (console_may_schedule)
877 EXPORT_SYMBOL(console_conditional_schedule);
879 void console_print(const char *s)
881 printk(KERN_EMERG "%s", s);
883 EXPORT_SYMBOL(console_print);
885 void console_unblank(void)
890 * console_unblank can no longer be called in interrupt context unless
891 * oops_in_progress is set to 1..
893 if (oops_in_progress) {
894 if (down_trylock(&console_sem) != 0)
897 acquire_console_sem();
900 console_may_schedule = 0;
901 for (c = console_drivers; c != NULL; c = c->next)
902 if ((c->flags & CON_ENABLED) && c->unblank)
904 release_console_sem();
908 * Return the console tty driver structure and its associated index
910 struct tty_driver *console_device(int *index)
913 struct tty_driver *driver = NULL;
915 acquire_console_sem();
916 for (c = console_drivers; c != NULL; c = c->next) {
919 driver = c->device(c, index);
923 release_console_sem();
928 * Prevent further output on the passed console device so that (for example)
929 * serial drivers can disable console output before suspending a port, and can
930 * re-enable output afterwards.
932 void console_stop(struct console *console)
934 acquire_console_sem();
935 console->flags &= ~CON_ENABLED;
936 release_console_sem();
938 EXPORT_SYMBOL(console_stop);
940 void console_start(struct console *console)
942 acquire_console_sem();
943 console->flags |= CON_ENABLED;
944 release_console_sem();
946 EXPORT_SYMBOL(console_start);
949 * The console driver calls this routine during kernel initialization
950 * to register the console printing procedure with printk() and to
951 * print any messages that were printed by the kernel before the
952 * console driver was initialized.
954 void register_console(struct console *console)
959 if (preferred_console < 0)
960 preferred_console = selected_console;
963 * See if we want to use this console driver. If we
964 * didn't select a console we take the first one
965 * that registers here.
967 if (preferred_console < 0) {
968 if (console->index < 0)
970 if (console->setup == NULL ||
971 console->setup(console, NULL) == 0) {
972 console->flags |= CON_ENABLED | CON_CONSDEV;
973 preferred_console = 0;
978 * See if this console matches one we selected on
981 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
983 if (strcmp(console_cmdline[i].name, console->name) != 0)
985 if (console->index >= 0 &&
986 console->index != console_cmdline[i].index)
988 if (console->index < 0)
989 console->index = console_cmdline[i].index;
990 if (console->setup &&
991 console->setup(console, console_cmdline[i].options) != 0)
993 console->flags |= CON_ENABLED;
994 console->index = console_cmdline[i].index;
995 if (i == selected_console) {
996 console->flags |= CON_CONSDEV;
997 preferred_console = selected_console;
1002 if (!(console->flags & CON_ENABLED))
1005 if (console_drivers && (console_drivers->flags & CON_BOOT)) {
1006 unregister_console(console_drivers);
1007 console->flags &= ~CON_PRINTBUFFER;
1011 * Put this console in the list - keep the
1012 * preferred driver at the head of the list.
1014 acquire_console_sem();
1015 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1016 console->next = console_drivers;
1017 console_drivers = console;
1019 console->next->flags &= ~CON_CONSDEV;
1021 console->next = console_drivers->next;
1022 console_drivers->next = console;
1024 if (console->flags & CON_PRINTBUFFER) {
1026 * release_console_sem() will print out the buffered messages
1029 spin_lock_irqsave(&logbuf_lock, flags);
1030 con_start = log_start;
1031 spin_unlock_irqrestore(&logbuf_lock, flags);
1033 release_console_sem();
1035 EXPORT_SYMBOL(register_console);
1037 int unregister_console(struct console *console)
1039 struct console *a, *b;
1042 acquire_console_sem();
1043 if (console_drivers == console) {
1044 console_drivers=console->next;
1046 } else if (console_drivers) {
1047 for (a=console_drivers->next, b=console_drivers ;
1048 a; b=a, a=b->next) {
1057 /* If last console is removed, we re-enable picking the first
1058 * one that gets registered. Without that, pmac early boot console
1059 * would prevent fbcon from taking over.
1061 * If this isn't the last console and it has CON_CONSDEV set, we
1062 * need to set it on the next preferred console.
1064 if (console_drivers == NULL)
1065 preferred_console = selected_console;
1066 else if (console->flags & CON_CONSDEV)
1067 console_drivers->flags |= CON_CONSDEV;
1069 release_console_sem();
1072 EXPORT_SYMBOL(unregister_console);
1075 * tty_write_message - write a message to a certain tty, not just the console.
1076 * @tty: the destination tty_struct
1077 * @msg: the message to write
1079 * This is used for messages that need to be redirected to a specific tty.
1080 * We don't put it into the syslog queue right now maybe in the future if
1083 void tty_write_message(struct tty_struct *tty, char *msg)
1085 if (tty && tty->driver->write)
1086 tty->driver->write(tty, msg, strlen(msg));
1091 * printk rate limiting, lifted from the networking subsystem.
1093 * This enforces a rate limit: not more than one kernel message
1094 * every printk_ratelimit_jiffies to make a denial-of-service
1095 * attack impossible.
1097 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1099 static DEFINE_SPINLOCK(ratelimit_lock);
1100 static unsigned long toks = 10 * 5 * HZ;
1101 static unsigned long last_msg;
1103 unsigned long flags;
1104 unsigned long now = jiffies;
1106 spin_lock_irqsave(&ratelimit_lock, flags);
1107 toks += now - last_msg;
1109 if (toks > (ratelimit_burst * ratelimit_jiffies))
1110 toks = ratelimit_burst * ratelimit_jiffies;
1111 if (toks >= ratelimit_jiffies) {
1115 toks -= ratelimit_jiffies;
1116 spin_unlock_irqrestore(&ratelimit_lock, flags);
1118 printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1122 spin_unlock_irqrestore(&ratelimit_lock, flags);
1125 EXPORT_SYMBOL(__printk_ratelimit);
1127 /* minimum time in jiffies between messages */
1128 int printk_ratelimit_jiffies = 5 * HZ;
1130 /* number of messages we send before ratelimiting */
1131 int printk_ratelimit_burst = 10;
1133 int printk_ratelimit(void)
1135 return __printk_ratelimit(printk_ratelimit_jiffies,
1136 printk_ratelimit_burst);
1138 EXPORT_SYMBOL(printk_ratelimit);