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 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
;
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 */
125 static int __init
log_buf_len_setup(char *str
)
127 unsigned long size
= memparse(str
, &str
);
131 size
= roundup_pow_of_two(size
);
132 if (size
> log_buf_len
) {
133 unsigned long start
, dest_idx
, offset
;
136 new_log_buf
= alloc_bootmem(size
);
138 printk(KERN_WARNING
"log_buf_len: allocation failed\n");
142 spin_lock_irqsave(&logbuf_lock
, flags
);
144 log_buf
= new_log_buf
;
146 offset
= start
= min(con_start
, log_start
);
148 while (start
!= log_end
) {
149 log_buf
[dest_idx
] = __log_buf
[start
& (__LOG_BUF_LEN
- 1)];
156 spin_unlock_irqrestore(&logbuf_lock
, flags
);
158 printk(KERN_NOTICE
"log_buf_len: %d\n", log_buf_len
);
164 __setup("log_buf_len=", log_buf_len_setup
);
167 * Commands to do_syslog:
169 * 0 -- Close the log. Currently a NOP.
170 * 1 -- Open the log. Currently a NOP.
171 * 2 -- Read from the log.
172 * 3 -- Read all messages remaining in the ring buffer.
173 * 4 -- Read and clear all messages remaining in the ring buffer
174 * 5 -- Clear ring buffer.
175 * 6 -- Disable printk's to console
176 * 7 -- Enable printk's to console
177 * 8 -- Set level of messages printed to console
178 * 9 -- Return number of unread characters in the log buffer
179 * 10 -- Return size of the log buffer
181 int do_syslog(int type
, char __user
*buf
, int len
)
183 unsigned long i
, j
, limit
, count
;
188 error
= security_syslog(type
);
193 case 0: /* Close log */
195 case 1: /* Open log */
197 case 2: /* Read from log */
204 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
208 error
= wait_event_interruptible(log_wait
,
209 (log_start
- log_end
));
213 spin_lock_irq(&logbuf_lock
);
214 while (!error
&& (log_start
!= log_end
) && i
< len
) {
215 c
= LOG_BUF(log_start
);
217 spin_unlock_irq(&logbuf_lock
);
218 error
= __put_user(c
,buf
);
222 spin_lock_irq(&logbuf_lock
);
224 spin_unlock_irq(&logbuf_lock
);
228 case 4: /* Read/clear last kernel messages */
231 case 3: /* Read last kernel messages */
238 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
243 if (count
> log_buf_len
)
245 spin_lock_irq(&logbuf_lock
);
246 if (count
> logged_chars
)
247 count
= logged_chars
;
252 * __put_user() could sleep, and while we sleep
253 * printk() could overwrite the messages
254 * we try to copy to user space. Therefore
255 * the messages are copied in reverse. <manfreds>
257 for (i
= 0; i
< count
&& !error
; i
++) {
259 if (j
+ log_buf_len
< log_end
)
262 spin_unlock_irq(&logbuf_lock
);
263 error
= __put_user(c
,&buf
[count
-1-i
]);
265 spin_lock_irq(&logbuf_lock
);
267 spin_unlock_irq(&logbuf_lock
);
272 int offset
= count
-error
;
273 /* buffer overflow during copy, correct user buffer. */
274 for (i
= 0; i
< error
; i
++) {
275 if (__get_user(c
,&buf
[i
+offset
]) ||
276 __put_user(c
,&buf
[i
])) {
284 case 5: /* Clear ring buffer */
287 case 6: /* Disable logging to console */
288 console_loglevel
= minimum_console_loglevel
;
290 case 7: /* Enable logging to console */
291 console_loglevel
= default_console_loglevel
;
293 case 8: /* Set level of messages printed to console */
295 if (len
< 1 || len
> 8)
297 if (len
< minimum_console_loglevel
)
298 len
= minimum_console_loglevel
;
299 console_loglevel
= len
;
302 case 9: /* Number of chars in the log buffer */
303 error
= log_end
- log_start
;
305 case 10: /* Size of the log buffer */
316 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
318 return do_syslog(type
, buf
, len
);
322 * Call the console drivers on a range of log_buf
324 static void __call_console_drivers(unsigned long start
, unsigned long end
)
328 for (con
= console_drivers
; con
; con
= con
->next
) {
329 if ((con
->flags
& CON_ENABLED
) && con
->write
)
330 con
->write(con
, &LOG_BUF(start
), end
- start
);
335 * Write out chars from start to end - 1 inclusive
337 static void _call_console_drivers(unsigned long start
,
338 unsigned long end
, int msg_log_level
)
340 if (msg_log_level
< console_loglevel
&&
341 console_drivers
&& start
!= end
) {
342 if ((start
& LOG_BUF_MASK
) > (end
& LOG_BUF_MASK
)) {
344 __call_console_drivers(start
& LOG_BUF_MASK
,
346 __call_console_drivers(0, end
& LOG_BUF_MASK
);
348 __call_console_drivers(start
, end
);
354 * Call the console drivers, asking them to write out
355 * log_buf[start] to log_buf[end - 1].
356 * The console_sem must be held.
358 static void call_console_drivers(unsigned long start
, unsigned long end
)
360 unsigned long cur_index
, start_print
;
361 static int msg_level
= -1;
363 if (((long)(start
- end
)) > 0)
368 while (cur_index
!= end
) {
369 if (msg_level
< 0 && ((end
- cur_index
) > 2) &&
370 LOG_BUF(cur_index
+ 0) == '<' &&
371 LOG_BUF(cur_index
+ 1) >= '0' &&
372 LOG_BUF(cur_index
+ 1) <= '7' &&
373 LOG_BUF(cur_index
+ 2) == '>') {
374 msg_level
= LOG_BUF(cur_index
+ 1) - '0';
376 start_print
= cur_index
;
378 while (cur_index
!= end
) {
379 char c
= LOG_BUF(cur_index
);
385 * printk() has already given us loglevel tags in
386 * the buffer. This code is here in case the
387 * log buffer has wrapped right round and scribbled
390 msg_level
= default_message_loglevel
;
392 _call_console_drivers(start_print
, cur_index
, msg_level
);
394 start_print
= cur_index
;
399 _call_console_drivers(start_print
, end
, msg_level
);
402 static void emit_log_char(char c
)
404 LOG_BUF(log_end
) = c
;
406 if (log_end
- log_start
> log_buf_len
)
407 log_start
= log_end
- log_buf_len
;
408 if (log_end
- con_start
> log_buf_len
)
409 con_start
= log_end
- log_buf_len
;
410 if (logged_chars
< log_buf_len
)
415 * Zap console related locks when oopsing. Only zap at most once
416 * every 10 seconds, to leave time for slow consoles to print a
419 static void zap_locks(void)
421 static unsigned long oops_timestamp
;
423 if (time_after_eq(jiffies
, oops_timestamp
) &&
424 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
427 oops_timestamp
= jiffies
;
429 /* If a crash is occurring, make sure we can't deadlock */
430 spin_lock_init(&logbuf_lock
);
431 /* And make sure that we print immediately */
432 init_MUTEX(&console_sem
);
435 #if defined(CONFIG_PRINTK_TIME)
436 static int printk_time
= 1;
438 static int printk_time
= 0;
441 static int __init
printk_time_setup(char *str
)
449 __setup("time", printk_time_setup
);
451 __attribute__((weak
)) unsigned long long printk_clock(void)
453 return sched_clock();
457 * printk - print a kernel message
458 * @fmt: format string
460 * This is printk. It can be called from any context. We want it to work.
462 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
463 * call the console drivers. If we fail to get the semaphore we place the output
464 * into the log buffer and return. The current holder of the console_sem will
465 * notice the new output in release_console_sem() and will send it to the
466 * consoles before releasing the semaphore.
468 * One effect of this deferred printing is that code which calls printk() and
469 * then changes console_loglevel may break. This is because console_loglevel
470 * is inspected when the actual printing occurs.
476 asmlinkage
int printk(const char *fmt
, ...)
482 r
= vprintk(fmt
, args
);
488 /* cpu currently holding logbuf_lock */
489 static volatile unsigned int printk_cpu
= UINT_MAX
;
491 asmlinkage
int vprintk(const char *fmt
, va_list args
)
496 static char printk_buf
[1024];
497 static int log_level_unknown
= 1;
500 if (unlikely(oops_in_progress
) && printk_cpu
== smp_processor_id())
501 /* If a crash is occurring during printk() on this CPU,
502 * make sure we can't deadlock */
505 /* This stops the holder of console_sem just where we want him */
506 spin_lock_irqsave(&logbuf_lock
, flags
);
507 printk_cpu
= smp_processor_id();
509 /* Emit the output into the temporary buffer */
510 printed_len
= vscnprintf(printk_buf
, sizeof(printk_buf
), fmt
, args
);
513 * Copy the output into log_buf. If the caller didn't provide
514 * appropriate log level tags, we insert them here
516 for (p
= printk_buf
; *p
; p
++) {
517 if (log_level_unknown
) {
518 /* log_level_unknown signals the start of a new line */
523 unsigned long long t
;
524 unsigned long nanosec_rem
;
527 * force the log level token to be
528 * before the time output.
530 if (p
[0] == '<' && p
[1] >='0' &&
531 p
[1] <= '7' && p
[2] == '>') {
536 loglev_char
= default_message_loglevel
540 nanosec_rem
= do_div(t
, 1000000000);
547 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
551 if (p
[0] != '<' || p
[1] < '0' ||
552 p
[1] > '7' || p
[2] != '>') {
554 emit_log_char(default_message_loglevel
560 log_level_unknown
= 0;
566 log_level_unknown
= 1;
569 if (!cpu_online(smp_processor_id())) {
571 * Some console drivers may assume that per-cpu resources have
572 * been allocated. So don't allow them to be called by this
573 * CPU until it is officially up. We shouldn't be calling into
574 * random console drivers on a CPU which doesn't exist yet..
576 printk_cpu
= UINT_MAX
;
577 spin_unlock_irqrestore(&logbuf_lock
, flags
);
580 if (!down_trylock(&console_sem
)) {
583 * We own the drivers. We can drop the spinlock and let
584 * release_console_sem() print the text
586 printk_cpu
= UINT_MAX
;
587 spin_unlock_irqrestore(&logbuf_lock
, flags
);
588 console_may_schedule
= 0;
589 release_console_sem();
592 * Someone else owns the drivers. We drop the spinlock, which
593 * allows the semaphore holder to proceed and to call the
594 * console drivers with the output which we just produced.
596 printk_cpu
= UINT_MAX
;
597 spin_unlock_irqrestore(&logbuf_lock
, flags
);
603 EXPORT_SYMBOL(printk
);
604 EXPORT_SYMBOL(vprintk
);
608 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
613 int do_syslog(int type
, char __user
*buf
, int len
)
618 static void call_console_drivers(unsigned long start
, unsigned long end
)
625 * Set up a list of consoles. Called from init/main.c
627 static int __init
console_setup(char *str
)
629 char name
[sizeof(console_cmdline
[0].name
)];
634 * Decode str into name, index, options.
636 if (str
[0] >= '0' && str
[0] <= '9') {
637 strcpy(name
, "ttyS");
638 strncpy(name
+ 4, str
, sizeof(name
) - 5);
640 strncpy(name
, str
, sizeof(name
) - 1);
642 name
[sizeof(name
) - 1] = 0;
643 if ((options
= strchr(str
, ',')) != NULL
)
646 if (!strcmp(str
, "ttya"))
647 strcpy(name
, "ttyS0");
648 if (!strcmp(str
, "ttyb"))
649 strcpy(name
, "ttyS1");
651 for (s
= name
; *s
; s
++)
652 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
654 idx
= simple_strtoul(s
, NULL
, 10);
657 add_preferred_console(name
, idx
, options
);
660 __setup("console=", console_setup
);
663 * add_preferred_console - add a device to the list of preferred consoles.
666 * @options: options for this console
668 * The last preferred console added will be used for kernel messages
669 * and stdin/out/err for init. Normally this is used by console_setup
670 * above to handle user-supplied console arguments; however it can also
671 * be used by arch-specific code either to override the user or more
672 * commonly to provide a default console (ie from PROM variables) when
673 * the user has not supplied one.
675 int __init
add_preferred_console(char *name
, int idx
, char *options
)
677 struct console_cmdline
*c
;
681 * See if this tty is not yet registered, and
682 * if we have a slot free.
684 for(i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
685 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
686 console_cmdline
[i
].index
== idx
) {
687 selected_console
= i
;
690 if (i
== MAX_CMDLINECONSOLES
)
692 selected_console
= i
;
693 c
= &console_cmdline
[i
];
694 memcpy(c
->name
, name
, sizeof(c
->name
));
695 c
->name
[sizeof(c
->name
) - 1] = 0;
696 c
->options
= options
;
702 * acquire_console_sem - lock the console system for exclusive use.
704 * Acquires a semaphore which guarantees that the caller has
705 * exclusive access to the console system and the console_drivers list.
707 * Can sleep, returns nothing.
709 void acquire_console_sem(void)
715 console_may_schedule
= 1;
717 EXPORT_SYMBOL(acquire_console_sem
);
719 int try_acquire_console_sem(void)
721 if (down_trylock(&console_sem
))
724 console_may_schedule
= 0;
727 EXPORT_SYMBOL(try_acquire_console_sem
);
729 int is_console_locked(void)
731 return console_locked
;
733 EXPORT_SYMBOL(is_console_locked
);
736 * release_console_sem - unlock the console system
738 * Releases the semaphore which the caller holds on the console system
739 * and the console driver list.
741 * While the semaphore was held, console output may have been buffered
742 * by printk(). If this is the case, release_console_sem() emits
743 * the output prior to releasing the semaphore.
745 * If there is output waiting for klogd, we wake it up.
747 * release_console_sem() may be called from any context.
749 void release_console_sem(void)
752 unsigned long _con_start
, _log_end
;
753 unsigned long wake_klogd
= 0;
756 spin_lock_irqsave(&logbuf_lock
, flags
);
757 wake_klogd
|= log_start
- log_end
;
758 if (con_start
== log_end
)
759 break; /* Nothing to print */
760 _con_start
= con_start
;
762 con_start
= log_end
; /* Flush */
763 spin_unlock(&logbuf_lock
);
764 call_console_drivers(_con_start
, _log_end
);
765 local_irq_restore(flags
);
768 console_may_schedule
= 0;
770 spin_unlock_irqrestore(&logbuf_lock
, flags
);
771 if (wake_klogd
&& !oops_in_progress
&& waitqueue_active(&log_wait
))
772 wake_up_interruptible(&log_wait
);
774 EXPORT_SYMBOL(release_console_sem
);
777 * console_conditional_schedule - yield the CPU if required
779 * If the console code is currently allowed to sleep, and
780 * if this CPU should yield the CPU to another task, do
783 * Must be called within acquire_console_sem().
785 void __sched
console_conditional_schedule(void)
787 if (console_may_schedule
)
790 EXPORT_SYMBOL(console_conditional_schedule
);
792 void console_print(const char *s
)
794 printk(KERN_EMERG
"%s", s
);
796 EXPORT_SYMBOL(console_print
);
798 void console_unblank(void)
803 * console_unblank can no longer be called in interrupt context unless
804 * oops_in_progress is set to 1..
806 if (oops_in_progress
) {
807 if (down_trylock(&console_sem
) != 0)
810 acquire_console_sem();
813 console_may_schedule
= 0;
814 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
)
815 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
817 release_console_sem();
821 * Return the console tty driver structure and its associated index
823 struct tty_driver
*console_device(int *index
)
826 struct tty_driver
*driver
= NULL
;
828 acquire_console_sem();
829 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
) {
832 driver
= c
->device(c
, index
);
836 release_console_sem();
841 * Prevent further output on the passed console device so that (for example)
842 * serial drivers can disable console output before suspending a port, and can
843 * re-enable output afterwards.
845 void console_stop(struct console
*console
)
847 acquire_console_sem();
848 console
->flags
&= ~CON_ENABLED
;
849 release_console_sem();
851 EXPORT_SYMBOL(console_stop
);
853 void console_start(struct console
*console
)
855 acquire_console_sem();
856 console
->flags
|= CON_ENABLED
;
857 release_console_sem();
859 EXPORT_SYMBOL(console_start
);
862 * The console driver calls this routine during kernel initialization
863 * to register the console printing procedure with printk() and to
864 * print any messages that were printed by the kernel before the
865 * console driver was initialized.
867 void register_console(struct console
*console
)
872 if (preferred_console
< 0)
873 preferred_console
= selected_console
;
876 * See if we want to use this console driver. If we
877 * didn't select a console we take the first one
878 * that registers here.
880 if (preferred_console
< 0) {
881 if (console
->index
< 0)
883 if (console
->setup
== NULL
||
884 console
->setup(console
, NULL
) == 0) {
885 console
->flags
|= CON_ENABLED
| CON_CONSDEV
;
886 preferred_console
= 0;
891 * See if this console matches one we selected on
894 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
896 if (strcmp(console_cmdline
[i
].name
, console
->name
) != 0)
898 if (console
->index
>= 0 &&
899 console
->index
!= console_cmdline
[i
].index
)
901 if (console
->index
< 0)
902 console
->index
= console_cmdline
[i
].index
;
903 if (console
->setup
&&
904 console
->setup(console
, console_cmdline
[i
].options
) != 0)
906 console
->flags
|= CON_ENABLED
;
907 console
->index
= console_cmdline
[i
].index
;
908 if (i
== selected_console
) {
909 console
->flags
|= CON_CONSDEV
;
910 preferred_console
= selected_console
;
915 if (!(console
->flags
& CON_ENABLED
))
918 if (console_drivers
&& (console_drivers
->flags
& CON_BOOT
)) {
919 unregister_console(console_drivers
);
920 console
->flags
&= ~CON_PRINTBUFFER
;
924 * Put this console in the list - keep the
925 * preferred driver at the head of the list.
927 acquire_console_sem();
928 if ((console
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
929 console
->next
= console_drivers
;
930 console_drivers
= console
;
932 console
->next
->flags
&= ~CON_CONSDEV
;
934 console
->next
= console_drivers
->next
;
935 console_drivers
->next
= console
;
937 if (console
->flags
& CON_PRINTBUFFER
) {
939 * release_console_sem() will print out the buffered messages
942 spin_lock_irqsave(&logbuf_lock
, flags
);
943 con_start
= log_start
;
944 spin_unlock_irqrestore(&logbuf_lock
, flags
);
946 release_console_sem();
948 EXPORT_SYMBOL(register_console
);
950 int unregister_console(struct console
*console
)
952 struct console
*a
, *b
;
955 acquire_console_sem();
956 if (console_drivers
== console
) {
957 console_drivers
=console
->next
;
959 } else if (console_drivers
) {
960 for (a
=console_drivers
->next
, b
=console_drivers
;
970 /* If last console is removed, we re-enable picking the first
971 * one that gets registered. Without that, pmac early boot console
972 * would prevent fbcon from taking over.
974 * If this isn't the last console and it has CON_CONSDEV set, we
975 * need to set it on the next preferred console.
977 if (console_drivers
== NULL
)
978 preferred_console
= selected_console
;
979 else if (console
->flags
& CON_CONSDEV
)
980 console_drivers
->flags
|= CON_CONSDEV
;
982 release_console_sem();
985 EXPORT_SYMBOL(unregister_console
);
988 * tty_write_message - write a message to a certain tty, not just the console.
989 * @tty: the destination tty_struct
990 * @msg: the message to write
992 * This is used for messages that need to be redirected to a specific tty.
993 * We don't put it into the syslog queue right now maybe in the future if
996 void tty_write_message(struct tty_struct
*tty
, char *msg
)
998 if (tty
&& tty
->driver
->write
)
999 tty
->driver
->write(tty
, msg
, strlen(msg
));
1004 * printk rate limiting, lifted from the networking subsystem.
1006 * This enforces a rate limit: not more than one kernel message
1007 * every printk_ratelimit_jiffies to make a denial-of-service
1008 * attack impossible.
1010 int __printk_ratelimit(int ratelimit_jiffies
, int ratelimit_burst
)
1012 static DEFINE_SPINLOCK(ratelimit_lock
);
1013 static unsigned long toks
= 10 * 5 * HZ
;
1014 static unsigned long last_msg
;
1016 unsigned long flags
;
1017 unsigned long now
= jiffies
;
1019 spin_lock_irqsave(&ratelimit_lock
, flags
);
1020 toks
+= now
- last_msg
;
1022 if (toks
> (ratelimit_burst
* ratelimit_jiffies
))
1023 toks
= ratelimit_burst
* ratelimit_jiffies
;
1024 if (toks
>= ratelimit_jiffies
) {
1028 toks
-= ratelimit_jiffies
;
1029 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1031 printk(KERN_WARNING
"printk: %d messages suppressed.\n", lost
);
1035 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1038 EXPORT_SYMBOL(__printk_ratelimit
);
1040 /* minimum time in jiffies between messages */
1041 int printk_ratelimit_jiffies
= 5 * HZ
;
1043 /* number of messages we send before ratelimiting */
1044 int printk_ratelimit_burst
= 10;
1046 int printk_ratelimit(void)
1048 return __printk_ratelimit(printk_ratelimit_jiffies
,
1049 printk_ratelimit_burst
);
1051 EXPORT_SYMBOL(printk_ratelimit
);