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/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.
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
69 static DECLARE_MUTEX(console_sem);
70 static DECLARE_MUTEX(secondary_console_sem);
71 struct console *console_drivers;
73 * This is used for debugging the mess that is the VT code by
74 * keeping track if we have the console semaphore held. It's
75 * definitely not the perfect debug tool (we don't know if _WE_
76 * hold it are racing, but it helps tracking those weird code
77 * path in the console code where we end up in places I want
78 * locked without the console sempahore held
80 static int console_locked, console_suspended;
83 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
84 * It is also used in interesting ways to provide interlocking in
85 * release_console_sem().
87 static DEFINE_SPINLOCK(logbuf_lock);
89 #define LOG_BUF_MASK (log_buf_len-1)
90 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
93 * The indices into log_buf are not constrained to log_buf_len - they
94 * must be masked before subscripting
96 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
97 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
98 static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */
101 * Array of consoles built from command line options (console=)
103 struct console_cmdline
105 char name[8]; /* Name of the driver */
106 int index; /* Minor dev. to use */
107 char *options; /* Options for the driver */
110 #define MAX_CMDLINECONSOLES 8
112 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
113 static int selected_console = -1;
114 static int preferred_console = -1;
116 /* Flag: console code may call schedule() */
117 static int console_may_schedule;
121 static char __log_buf[__LOG_BUF_LEN];
122 static char *log_buf = __log_buf;
123 static int log_buf_len = __LOG_BUF_LEN;
124 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
126 static int __init log_buf_len_setup(char *str)
128 unsigned long size = memparse(str, &str);
132 size = roundup_pow_of_two(size);
133 if (size > log_buf_len) {
134 unsigned long start, dest_idx, offset;
137 new_log_buf = alloc_bootmem(size);
139 printk(KERN_WARNING "log_buf_len: allocation failed\n");
143 spin_lock_irqsave(&logbuf_lock, flags);
145 log_buf = new_log_buf;
147 offset = start = min(con_start, log_start);
149 while (start != log_end) {
150 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
157 spin_unlock_irqrestore(&logbuf_lock, flags);
159 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
165 __setup("log_buf_len=", log_buf_len_setup);
168 * Commands to do_syslog:
170 * 0 -- Close the log. Currently a NOP.
171 * 1 -- Open the log. Currently a NOP.
172 * 2 -- Read from the log.
173 * 3 -- Read all messages remaining in the ring buffer.
174 * 4 -- Read and clear all messages remaining in the ring buffer
175 * 5 -- Clear ring buffer.
176 * 6 -- Disable printk's to console
177 * 7 -- Enable printk's to console
178 * 8 -- Set level of messages printed to console
179 * 9 -- Return number of unread characters in the log buffer
180 * 10 -- Return size of the log buffer
182 int do_syslog(int type, char __user *buf, int len)
184 unsigned long i, j, limit, count;
189 error = security_syslog(type);
194 case 0: /* Close log */
196 case 1: /* Open log */
198 case 2: /* Read from log */
205 if (!access_ok(VERIFY_WRITE, buf, len)) {
209 error = wait_event_interruptible(log_wait,
210 (log_start - log_end));
214 spin_lock_irq(&logbuf_lock);
215 while (!error && (log_start != log_end) && i < len) {
216 c = LOG_BUF(log_start);
218 spin_unlock_irq(&logbuf_lock);
219 error = __put_user(c,buf);
223 spin_lock_irq(&logbuf_lock);
225 spin_unlock_irq(&logbuf_lock);
229 case 4: /* Read/clear last kernel messages */
232 case 3: /* Read last kernel messages */
239 if (!access_ok(VERIFY_WRITE, buf, len)) {
244 if (count > log_buf_len)
246 spin_lock_irq(&logbuf_lock);
247 if (count > logged_chars)
248 count = logged_chars;
253 * __put_user() could sleep, and while we sleep
254 * printk() could overwrite the messages
255 * we try to copy to user space. Therefore
256 * the messages are copied in reverse. <manfreds>
258 for (i = 0; i < count && !error; i++) {
260 if (j + log_buf_len < log_end)
263 spin_unlock_irq(&logbuf_lock);
264 error = __put_user(c,&buf[count-1-i]);
266 spin_lock_irq(&logbuf_lock);
268 spin_unlock_irq(&logbuf_lock);
273 int offset = count-error;
274 /* buffer overflow during copy, correct user buffer. */
275 for (i = 0; i < error; i++) {
276 if (__get_user(c,&buf[i+offset]) ||
277 __put_user(c,&buf[i])) {
285 case 5: /* Clear ring buffer */
288 case 6: /* Disable logging to console */
289 console_loglevel = minimum_console_loglevel;
291 case 7: /* Enable logging to console */
292 console_loglevel = default_console_loglevel;
294 case 8: /* Set level of messages printed to console */
296 if (len < 1 || len > 8)
298 if (len < minimum_console_loglevel)
299 len = minimum_console_loglevel;
300 console_loglevel = len;
303 case 9: /* Number of chars in the log buffer */
304 error = log_end - log_start;
306 case 10: /* Size of the log buffer */
317 asmlinkage long sys_syslog(int type, char __user *buf, int len)
319 return do_syslog(type, buf, len);
323 * Call the console drivers on a range of log_buf
325 static void __call_console_drivers(unsigned long start, unsigned long end)
329 for (con = console_drivers; con; con = con->next) {
330 if ((con->flags & CON_ENABLED) && con->write &&
331 (cpu_online(smp_processor_id()) ||
332 (con->flags & CON_ANYTIME)))
333 con->write(con, &LOG_BUF(start), end - start);
338 * Write out chars from start to end - 1 inclusive
340 static void _call_console_drivers(unsigned long start,
341 unsigned long end, int msg_log_level)
343 if (msg_log_level < console_loglevel &&
344 console_drivers && start != end) {
345 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
347 __call_console_drivers(start & LOG_BUF_MASK,
349 __call_console_drivers(0, end & LOG_BUF_MASK);
351 __call_console_drivers(start, end);
357 * Call the console drivers, asking them to write out
358 * log_buf[start] to log_buf[end - 1].
359 * The console_sem must be held.
361 static void call_console_drivers(unsigned long start, unsigned long end)
363 unsigned long cur_index, start_print;
364 static int msg_level = -1;
366 BUG_ON(((long)(start - end)) > 0);
370 while (cur_index != end) {
371 if (msg_level < 0 && ((end - cur_index) > 2) &&
372 LOG_BUF(cur_index + 0) == '<' &&
373 LOG_BUF(cur_index + 1) >= '0' &&
374 LOG_BUF(cur_index + 1) <= '7' &&
375 LOG_BUF(cur_index + 2) == '>') {
376 msg_level = LOG_BUF(cur_index + 1) - '0';
378 start_print = cur_index;
380 while (cur_index != end) {
381 char c = LOG_BUF(cur_index);
387 * printk() has already given us loglevel tags in
388 * the buffer. This code is here in case the
389 * log buffer has wrapped right round and scribbled
392 msg_level = default_message_loglevel;
394 _call_console_drivers(start_print, cur_index, msg_level);
396 start_print = cur_index;
401 _call_console_drivers(start_print, end, msg_level);
404 static void emit_log_char(char c)
406 LOG_BUF(log_end) = c;
408 if (log_end - log_start > log_buf_len)
409 log_start = log_end - log_buf_len;
410 if (log_end - con_start > log_buf_len)
411 con_start = log_end - log_buf_len;
412 if (logged_chars < log_buf_len)
417 * Zap console related locks when oopsing. Only zap at most once
418 * every 10 seconds, to leave time for slow consoles to print a
421 static void zap_locks(void)
423 static unsigned long oops_timestamp;
425 if (time_after_eq(jiffies, oops_timestamp) &&
426 !time_after(jiffies, oops_timestamp + 30 * HZ))
429 oops_timestamp = jiffies;
431 /* If a crash is occurring, make sure we can't deadlock */
432 spin_lock_init(&logbuf_lock);
433 /* And make sure that we print immediately */
434 init_MUTEX(&console_sem);
437 #if defined(CONFIG_PRINTK_TIME)
438 static int printk_time = 1;
440 static int printk_time = 0;
443 static int __init printk_time_setup(char *str)
451 __setup("time", printk_time_setup);
453 __attribute__((weak)) unsigned long long printk_clock(void)
455 return sched_clock();
458 /* Check if we have any console registered that can be called early in boot. */
459 static int have_callable_console(void)
463 for (con = console_drivers; con; con = con->next)
464 if (con->flags & CON_ANYTIME)
471 * printk - print a kernel message
472 * @fmt: format string
474 * This is printk. It can be called from any context. We want it to work.
476 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
477 * call the console drivers. If we fail to get the semaphore we place the output
478 * into the log buffer and return. The current holder of the console_sem will
479 * notice the new output in release_console_sem() and will send it to the
480 * consoles before releasing the semaphore.
482 * One effect of this deferred printing is that code which calls printk() and
483 * then changes console_loglevel may break. This is because console_loglevel
484 * is inspected when the actual printing occurs.
490 asmlinkage int printk(const char *fmt, ...)
496 r = vprintk(fmt, args);
502 /* cpu currently holding logbuf_lock */
503 static volatile unsigned int printk_cpu = UINT_MAX;
505 asmlinkage int vprintk(const char *fmt, va_list args)
510 static char printk_buf[1024];
511 static int log_level_unknown = 1;
514 if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
515 /* If a crash is occurring during printk() on this CPU,
516 * make sure we can't deadlock */
519 /* This stops the holder of console_sem just where we want him */
520 spin_lock_irqsave(&logbuf_lock, flags);
521 printk_cpu = smp_processor_id();
523 /* Emit the output into the temporary buffer */
524 printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
527 * Copy the output into log_buf. If the caller didn't provide
528 * appropriate log level tags, we insert them here
530 for (p = printk_buf; *p; p++) {
531 if (log_level_unknown) {
532 /* log_level_unknown signals the start of a new line */
537 unsigned long long t;
538 unsigned long nanosec_rem;
541 * force the log level token to be
542 * before the time output.
544 if (p[0] == '<' && p[1] >='0' &&
545 p[1] <= '7' && p[2] == '>') {
550 loglev_char = default_message_loglevel
554 nanosec_rem = do_div(t, 1000000000);
561 for (tp = tbuf; tp < tbuf + tlen; tp++)
565 if (p[0] != '<' || p[1] < '0' ||
566 p[1] > '7' || p[2] != '>') {
568 emit_log_char(default_message_loglevel
574 log_level_unknown = 0;
580 log_level_unknown = 1;
583 if (!down_trylock(&console_sem)) {
585 * We own the drivers. We can drop the spinlock and
586 * let release_console_sem() print the text, maybe ...
589 printk_cpu = UINT_MAX;
590 spin_unlock_irqrestore(&logbuf_lock, flags);
593 * Console drivers may assume that per-cpu resources have
594 * been allocated. So unless they're explicitly marked as
595 * being able to cope (CON_ANYTIME) don't call them until
596 * this CPU is officially up.
598 if (cpu_online(smp_processor_id()) || have_callable_console()) {
599 console_may_schedule = 0;
600 release_console_sem();
602 /* Release by hand to avoid flushing the buffer. */
608 * Someone else owns the drivers. We drop the spinlock, which
609 * allows the semaphore holder to proceed and to call the
610 * console drivers with the output which we just produced.
612 printk_cpu = UINT_MAX;
613 spin_unlock_irqrestore(&logbuf_lock, flags);
619 EXPORT_SYMBOL(printk);
620 EXPORT_SYMBOL(vprintk);
624 asmlinkage long sys_syslog(int type, char __user *buf, int len)
629 int do_syslog(int type, char __user *buf, int len)
634 static void call_console_drivers(unsigned long start, unsigned long end)
641 * Set up a list of consoles. Called from init/main.c
643 static int __init console_setup(char *str)
645 char name[sizeof(console_cmdline[0].name)];
650 * Decode str into name, index, options.
652 if (str[0] >= '0' && str[0] <= '9') {
653 strcpy(name, "ttyS");
654 strncpy(name + 4, str, sizeof(name) - 5);
656 strncpy(name, str, sizeof(name) - 1);
658 name[sizeof(name) - 1] = 0;
659 if ((options = strchr(str, ',')) != NULL)
662 if (!strcmp(str, "ttya"))
663 strcpy(name, "ttyS0");
664 if (!strcmp(str, "ttyb"))
665 strcpy(name, "ttyS1");
667 for (s = name; *s; s++)
668 if ((*s >= '0' && *s <= '9') || *s == ',')
670 idx = simple_strtoul(s, NULL, 10);
673 add_preferred_console(name, idx, options);
676 __setup("console=", console_setup);
679 * add_preferred_console - add a device to the list of preferred consoles.
682 * @options: options for this console
684 * The last preferred console added will be used for kernel messages
685 * and stdin/out/err for init. Normally this is used by console_setup
686 * above to handle user-supplied console arguments; however it can also
687 * be used by arch-specific code either to override the user or more
688 * commonly to provide a default console (ie from PROM variables) when
689 * the user has not supplied one.
691 int __init add_preferred_console(char *name, int idx, char *options)
693 struct console_cmdline *c;
697 * See if this tty is not yet registered, and
698 * if we have a slot free.
700 for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
701 if (strcmp(console_cmdline[i].name, name) == 0 &&
702 console_cmdline[i].index == idx) {
703 selected_console = i;
706 if (i == MAX_CMDLINECONSOLES)
708 selected_console = i;
709 c = &console_cmdline[i];
710 memcpy(c->name, name, sizeof(c->name));
711 c->name[sizeof(c->name) - 1] = 0;
712 c->options = options;
718 * suspend_console - suspend the console subsystem
720 * This disables printk() while we go into suspend states
722 void suspend_console(void)
724 acquire_console_sem();
725 console_suspended = 1;
728 void resume_console(void)
730 console_suspended = 0;
731 release_console_sem();
735 * acquire_console_sem - lock the console system for exclusive use.
737 * Acquires a semaphore which guarantees that the caller has
738 * exclusive access to the console system and the console_drivers list.
740 * Can sleep, returns nothing.
742 void acquire_console_sem(void)
744 BUG_ON(in_interrupt());
745 if (console_suspended) {
746 down(&secondary_console_sem);
751 console_may_schedule = 1;
753 EXPORT_SYMBOL(acquire_console_sem);
755 int try_acquire_console_sem(void)
757 if (down_trylock(&console_sem))
760 console_may_schedule = 0;
763 EXPORT_SYMBOL(try_acquire_console_sem);
765 int is_console_locked(void)
767 return console_locked;
769 EXPORT_SYMBOL(is_console_locked);
772 * release_console_sem - unlock the console system
774 * Releases the semaphore which the caller holds on the console system
775 * and the console driver list.
777 * While the semaphore was held, console output may have been buffered
778 * by printk(). If this is the case, release_console_sem() emits
779 * the output prior to releasing the semaphore.
781 * If there is output waiting for klogd, we wake it up.
783 * release_console_sem() may be called from any context.
785 void release_console_sem(void)
788 unsigned long _con_start, _log_end;
789 unsigned long wake_klogd = 0;
791 if (console_suspended) {
792 up(&secondary_console_sem);
796 spin_lock_irqsave(&logbuf_lock, flags);
797 wake_klogd |= log_start - log_end;
798 if (con_start == log_end)
799 break; /* Nothing to print */
800 _con_start = con_start;
802 con_start = log_end; /* Flush */
803 spin_unlock(&logbuf_lock);
804 call_console_drivers(_con_start, _log_end);
805 local_irq_restore(flags);
808 console_may_schedule = 0;
810 spin_unlock_irqrestore(&logbuf_lock, flags);
811 if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
812 wake_up_interruptible(&log_wait);
814 EXPORT_SYMBOL(release_console_sem);
817 * console_conditional_schedule - yield the CPU if required
819 * If the console code is currently allowed to sleep, and
820 * if this CPU should yield the CPU to another task, do
823 * Must be called within acquire_console_sem().
825 void __sched console_conditional_schedule(void)
827 if (console_may_schedule)
830 EXPORT_SYMBOL(console_conditional_schedule);
832 void console_print(const char *s)
834 printk(KERN_EMERG "%s", s);
836 EXPORT_SYMBOL(console_print);
838 void console_unblank(void)
843 * console_unblank can no longer be called in interrupt context unless
844 * oops_in_progress is set to 1..
846 if (oops_in_progress) {
847 if (down_trylock(&console_sem) != 0)
850 acquire_console_sem();
853 console_may_schedule = 0;
854 for (c = console_drivers; c != NULL; c = c->next)
855 if ((c->flags & CON_ENABLED) && c->unblank)
857 release_console_sem();
861 * Return the console tty driver structure and its associated index
863 struct tty_driver *console_device(int *index)
866 struct tty_driver *driver = NULL;
868 acquire_console_sem();
869 for (c = console_drivers; c != NULL; c = c->next) {
872 driver = c->device(c, index);
876 release_console_sem();
881 * Prevent further output on the passed console device so that (for example)
882 * serial drivers can disable console output before suspending a port, and can
883 * re-enable output afterwards.
885 void console_stop(struct console *console)
887 acquire_console_sem();
888 console->flags &= ~CON_ENABLED;
889 release_console_sem();
891 EXPORT_SYMBOL(console_stop);
893 void console_start(struct console *console)
895 acquire_console_sem();
896 console->flags |= CON_ENABLED;
897 release_console_sem();
899 EXPORT_SYMBOL(console_start);
902 * The console driver calls this routine during kernel initialization
903 * to register the console printing procedure with printk() and to
904 * print any messages that were printed by the kernel before the
905 * console driver was initialized.
907 void register_console(struct console *console)
912 if (preferred_console < 0)
913 preferred_console = selected_console;
916 * See if we want to use this console driver. If we
917 * didn't select a console we take the first one
918 * that registers here.
920 if (preferred_console < 0) {
921 if (console->index < 0)
923 if (console->setup == NULL ||
924 console->setup(console, NULL) == 0) {
925 console->flags |= CON_ENABLED | CON_CONSDEV;
926 preferred_console = 0;
931 * See if this console matches one we selected on
934 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
936 if (strcmp(console_cmdline[i].name, console->name) != 0)
938 if (console->index >= 0 &&
939 console->index != console_cmdline[i].index)
941 if (console->index < 0)
942 console->index = console_cmdline[i].index;
943 if (console->setup &&
944 console->setup(console, console_cmdline[i].options) != 0)
946 console->flags |= CON_ENABLED;
947 console->index = console_cmdline[i].index;
948 if (i == selected_console) {
949 console->flags |= CON_CONSDEV;
950 preferred_console = selected_console;
955 if (!(console->flags & CON_ENABLED))
958 if (console_drivers && (console_drivers->flags & CON_BOOT)) {
959 unregister_console(console_drivers);
960 console->flags &= ~CON_PRINTBUFFER;
964 * Put this console in the list - keep the
965 * preferred driver at the head of the list.
967 acquire_console_sem();
968 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
969 console->next = console_drivers;
970 console_drivers = console;
972 console->next->flags &= ~CON_CONSDEV;
974 console->next = console_drivers->next;
975 console_drivers->next = console;
977 if (console->flags & CON_PRINTBUFFER) {
979 * release_console_sem() will print out the buffered messages
982 spin_lock_irqsave(&logbuf_lock, flags);
983 con_start = log_start;
984 spin_unlock_irqrestore(&logbuf_lock, flags);
986 release_console_sem();
988 EXPORT_SYMBOL(register_console);
990 int unregister_console(struct console *console)
992 struct console *a, *b;
995 acquire_console_sem();
996 if (console_drivers == console) {
997 console_drivers=console->next;
999 } else if (console_drivers) {
1000 for (a=console_drivers->next, b=console_drivers ;
1001 a; b=a, a=b->next) {
1010 /* If last console is removed, we re-enable picking the first
1011 * one that gets registered. Without that, pmac early boot console
1012 * would prevent fbcon from taking over.
1014 * If this isn't the last console and it has CON_CONSDEV set, we
1015 * need to set it on the next preferred console.
1017 if (console_drivers == NULL)
1018 preferred_console = selected_console;
1019 else if (console->flags & CON_CONSDEV)
1020 console_drivers->flags |= CON_CONSDEV;
1022 release_console_sem();
1025 EXPORT_SYMBOL(unregister_console);
1028 * tty_write_message - write a message to a certain tty, not just the console.
1029 * @tty: the destination tty_struct
1030 * @msg: the message to write
1032 * This is used for messages that need to be redirected to a specific tty.
1033 * We don't put it into the syslog queue right now maybe in the future if
1036 void tty_write_message(struct tty_struct *tty, char *msg)
1038 if (tty && tty->driver->write)
1039 tty->driver->write(tty, msg, strlen(msg));
1044 * printk rate limiting, lifted from the networking subsystem.
1046 * This enforces a rate limit: not more than one kernel message
1047 * every printk_ratelimit_jiffies to make a denial-of-service
1048 * attack impossible.
1050 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1052 static DEFINE_SPINLOCK(ratelimit_lock);
1053 static unsigned long toks = 10 * 5 * HZ;
1054 static unsigned long last_msg;
1056 unsigned long flags;
1057 unsigned long now = jiffies;
1059 spin_lock_irqsave(&ratelimit_lock, flags);
1060 toks += now - last_msg;
1062 if (toks > (ratelimit_burst * ratelimit_jiffies))
1063 toks = ratelimit_burst * ratelimit_jiffies;
1064 if (toks >= ratelimit_jiffies) {
1068 toks -= ratelimit_jiffies;
1069 spin_unlock_irqrestore(&ratelimit_lock, flags);
1071 printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1075 spin_unlock_irqrestore(&ratelimit_lock, flags);
1078 EXPORT_SYMBOL(__printk_ratelimit);
1080 /* minimum time in jiffies between messages */
1081 int printk_ratelimit_jiffies = 5 * HZ;
1083 /* number of messages we send before ratelimiting */
1084 int printk_ratelimit_burst = 10;
1086 int printk_ratelimit(void)
1088 return __printk_ratelimit(printk_ratelimit_jiffies,
1089 printk_ratelimit_burst);
1091 EXPORT_SYMBOL(printk_ratelimit);