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 * 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>
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 */
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
)];
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);
141 strncpy(name
, str
, sizeof(name
) - 1);
142 name
[sizeof(name
) - 1] = 0;
143 if ((options
= strchr(str
, ',')) != NULL
)
146 if (!strcmp(str
, "ttya"))
147 strcpy(name
, "ttyS0");
148 if (!strcmp(str
, "ttyb"))
149 strcpy(name
, "ttyS1");
151 for (s
= name
; *s
; s
++)
152 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
154 idx
= simple_strtoul(s
, NULL
, 10);
157 add_preferred_console(name
, idx
, options
);
161 __setup("console=", console_setup
);
163 static int __init
log_buf_len_setup(char *str
)
165 unsigned long size
= memparse(str
, &str
);
169 size
= roundup_pow_of_two(size
);
170 if (size
> log_buf_len
) {
171 unsigned long start
, dest_idx
, offset
;
174 new_log_buf
= alloc_bootmem(size
);
176 printk(KERN_WARNING
"log_buf_len: allocation failed\n");
180 spin_lock_irqsave(&logbuf_lock
, flags
);
182 log_buf
= new_log_buf
;
184 offset
= start
= min(con_start
, log_start
);
186 while (start
!= log_end
) {
187 log_buf
[dest_idx
] = __log_buf
[start
& (__LOG_BUF_LEN
- 1)];
194 spin_unlock_irqrestore(&logbuf_lock
, flags
);
196 printk(KERN_NOTICE
"log_buf_len: %d\n", log_buf_len
);
202 __setup("log_buf_len=", log_buf_len_setup
);
205 * Commands to do_syslog:
207 * 0 -- Close the log. Currently a NOP.
208 * 1 -- Open the log. Currently a NOP.
209 * 2 -- Read from the log.
210 * 3 -- Read all messages remaining in the ring buffer.
211 * 4 -- Read and clear all messages remaining in the ring buffer
212 * 5 -- Clear ring buffer.
213 * 6 -- Disable printk's to console
214 * 7 -- Enable printk's to console
215 * 8 -- Set level of messages printed to console
216 * 9 -- Return number of unread characters in the log buffer
217 * 10 -- Return size of the log buffer
219 int do_syslog(int type
, char __user
*buf
, int len
)
221 unsigned long i
, j
, limit
, count
;
226 error
= security_syslog(type
);
231 case 0: /* Close log */
233 case 1: /* Open log */
235 case 2: /* Read from log */
242 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
246 error
= wait_event_interruptible(log_wait
,
247 (log_start
- log_end
));
251 spin_lock_irq(&logbuf_lock
);
252 while (!error
&& (log_start
!= log_end
) && i
< len
) {
253 c
= LOG_BUF(log_start
);
255 spin_unlock_irq(&logbuf_lock
);
256 error
= __put_user(c
,buf
);
260 spin_lock_irq(&logbuf_lock
);
262 spin_unlock_irq(&logbuf_lock
);
266 case 4: /* Read/clear last kernel messages */
269 case 3: /* Read last kernel messages */
276 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
281 if (count
> log_buf_len
)
283 spin_lock_irq(&logbuf_lock
);
284 if (count
> logged_chars
)
285 count
= logged_chars
;
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
++) {
297 if (j
+ log_buf_len
< log_end
)
300 spin_unlock_irq(&logbuf_lock
);
301 error
= __put_user(c
,&buf
[count
-1-i
]);
303 spin_lock_irq(&logbuf_lock
);
305 spin_unlock_irq(&logbuf_lock
);
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
])) {
322 case 5: /* Clear ring buffer */
325 case 6: /* Disable logging to console */
326 console_loglevel
= minimum_console_loglevel
;
328 case 7: /* Enable logging to console */
329 console_loglevel
= default_console_loglevel
;
331 case 8: /* Set level of messages printed to console */
333 if (len
< 1 || len
> 8)
335 if (len
< minimum_console_loglevel
)
336 len
= minimum_console_loglevel
;
337 console_loglevel
= len
;
340 case 9: /* Number of chars in the log buffer */
341 error
= log_end
- log_start
;
343 case 10: /* Size of the log buffer */
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
)
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
)) {
382 __call_console_drivers(start
& LOG_BUF_MASK
,
384 __call_console_drivers(0, end
& LOG_BUF_MASK
);
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)
406 while (cur_index
!= end
) {
407 if (msg_level
< 0 && ((end
- cur_index
) > 2) &&
408 LOG_BUF(cur_index
+ 0) == '<' &&
409 LOG_BUF(cur_index
+ 1) >= '0' &&
410 LOG_BUF(cur_index
+ 1) <= '7' &&
411 LOG_BUF(cur_index
+ 2) == '>') {
412 msg_level
= LOG_BUF(cur_index
+ 1) - '0';
414 start_print
= cur_index
;
416 while (cur_index
!= end
) {
417 char c
= LOG_BUF(cur_index
);
423 * printk() has already given us loglevel tags in
424 * the buffer. This code is here in case the
425 * log buffer has wrapped right round and scribbled
428 msg_level
= default_message_loglevel
;
430 _call_console_drivers(start_print
, cur_index
, msg_level
);
432 start_print
= cur_index
;
437 _call_console_drivers(start_print
, end
, msg_level
);
440 static void emit_log_char(char c
)
442 LOG_BUF(log_end
) = c
;
444 if (log_end
- log_start
> log_buf_len
)
445 log_start
= log_end
- log_buf_len
;
446 if (log_end
- con_start
> log_buf_len
)
447 con_start
= log_end
- log_buf_len
;
448 if (logged_chars
< log_buf_len
)
453 * Zap console related locks when oopsing. Only zap at most once
454 * every 10 seconds, to leave time for slow consoles to print a
457 static void zap_locks(void)
459 static unsigned long oops_timestamp
;
461 if (time_after_eq(jiffies
, oops_timestamp
) &&
462 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
465 oops_timestamp
= jiffies
;
467 /* If a crash is occurring, make sure we can't deadlock */
468 spin_lock_init(&logbuf_lock
);
469 /* And make sure that we print immediately */
470 init_MUTEX(&console_sem
);
473 #if defined(CONFIG_PRINTK_TIME)
474 static int printk_time
= 1;
476 static int printk_time
= 0;
479 static int __init
printk_time_setup(char *str
)
487 __setup("time", printk_time_setup
);
489 __attribute__((weak
)) unsigned long long printk_clock(void)
491 return sched_clock();
495 * This is printk. It can be called from any context. We want it to work.
497 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
498 * call the console drivers. If we fail to get the semaphore we place the output
499 * into the log buffer and return. The current holder of the console_sem will
500 * notice the new output in release_console_sem() and will send it to the
501 * consoles before releasing the semaphore.
503 * One effect of this deferred printing is that code which calls printk() and
504 * then changes console_loglevel may break. This is because console_loglevel
505 * is inspected when the actual printing occurs.
508 asmlinkage
int printk(const char *fmt
, ...)
514 r
= vprintk(fmt
, args
);
520 /* cpu currently holding logbuf_lock */
521 static volatile unsigned int printk_cpu
= UINT_MAX
;
523 asmlinkage
int vprintk(const char *fmt
, va_list args
)
528 static char printk_buf
[1024];
529 static int log_level_unknown
= 1;
532 if (unlikely(oops_in_progress
) && printk_cpu
== smp_processor_id())
533 /* If a crash is occurring during printk() on this CPU,
534 * make sure we can't deadlock */
537 /* This stops the holder of console_sem just where we want him */
538 spin_lock_irqsave(&logbuf_lock
, flags
);
539 printk_cpu
= smp_processor_id();
541 /* Emit the output into the temporary buffer */
542 printed_len
= vscnprintf(printk_buf
, sizeof(printk_buf
), fmt
, args
);
545 * Copy the output into log_buf. If the caller didn't provide
546 * appropriate log level tags, we insert them here
548 for (p
= printk_buf
; *p
; p
++) {
549 if (log_level_unknown
) {
550 /* log_level_unknown signals the start of a new line */
555 unsigned long long t
;
556 unsigned long nanosec_rem
;
559 * force the log level token to be
560 * before the time output.
562 if (p
[0] == '<' && p
[1] >='0' &&
563 p
[1] <= '7' && p
[2] == '>') {
568 loglev_char
= default_message_loglevel
572 nanosec_rem
= do_div(t
, 1000000000);
579 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
581 printed_len
+= tlen
- 3;
583 if (p
[0] != '<' || p
[1] < '0' ||
584 p
[1] > '7' || p
[2] != '>') {
586 emit_log_char(default_message_loglevel
592 log_level_unknown
= 0;
598 log_level_unknown
= 1;
601 if (!cpu_online(smp_processor_id())) {
603 * Some console drivers may assume that per-cpu resources have
604 * been allocated. So don't allow them to be called by this
605 * CPU until it is officially up. We shouldn't be calling into
606 * random console drivers on a CPU which doesn't exist yet..
608 printk_cpu
= UINT_MAX
;
609 spin_unlock_irqrestore(&logbuf_lock
, flags
);
612 if (!down_trylock(&console_sem
)) {
615 * We own the drivers. We can drop the spinlock and let
616 * release_console_sem() print the text
618 printk_cpu
= UINT_MAX
;
619 spin_unlock_irqrestore(&logbuf_lock
, flags
);
620 console_may_schedule
= 0;
621 release_console_sem();
624 * Someone else owns the drivers. We drop the spinlock, which
625 * allows the semaphore holder to proceed and to call the
626 * console drivers with the output which we just produced.
628 printk_cpu
= UINT_MAX
;
629 spin_unlock_irqrestore(&logbuf_lock
, flags
);
635 EXPORT_SYMBOL(printk
);
636 EXPORT_SYMBOL(vprintk
);
640 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
645 int do_syslog(int type
, char __user
*buf
, int len
)
650 static void call_console_drivers(unsigned long start
, unsigned long end
)
657 * add_preferred_console - add a device to the list of preferred consoles.
659 * The last preferred console added will be used for kernel messages
660 * and stdin/out/err for init. Normally this is used by console_setup
661 * above to handle user-supplied console arguments; however it can also
662 * be used by arch-specific code either to override the user or more
663 * commonly to provide a default console (ie from PROM variables) when
664 * the user has not supplied one.
666 int __init
add_preferred_console(char *name
, int idx
, char *options
)
668 struct console_cmdline
*c
;
672 * See if this tty is not yet registered, and
673 * if we have a slot free.
675 for(i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
676 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
677 console_cmdline
[i
].index
== idx
) {
678 selected_console
= i
;
681 if (i
== MAX_CMDLINECONSOLES
)
683 selected_console
= i
;
684 c
= &console_cmdline
[i
];
685 memcpy(c
->name
, name
, sizeof(c
->name
));
686 c
->name
[sizeof(c
->name
) - 1] = 0;
687 c
->options
= options
;
693 * acquire_console_sem - lock the console system for exclusive use.
695 * Acquires a semaphore which guarantees that the caller has
696 * exclusive access to the console system and the console_drivers list.
698 * Can sleep, returns nothing.
700 void acquire_console_sem(void)
706 console_may_schedule
= 1;
708 EXPORT_SYMBOL(acquire_console_sem
);
710 int try_acquire_console_sem(void)
712 if (down_trylock(&console_sem
))
715 console_may_schedule
= 0;
718 EXPORT_SYMBOL(try_acquire_console_sem
);
720 int is_console_locked(void)
722 return console_locked
;
724 EXPORT_SYMBOL(is_console_locked
);
727 * release_console_sem - unlock the console system
729 * Releases the semaphore which the caller holds on the console system
730 * and the console driver list.
732 * While the semaphore was held, console output may have been buffered
733 * by printk(). If this is the case, release_console_sem() emits
734 * the output prior to releasing the semaphore.
736 * If there is output waiting for klogd, we wake it up.
738 * release_console_sem() may be called from any context.
740 void release_console_sem(void)
743 unsigned long _con_start
, _log_end
;
744 unsigned long wake_klogd
= 0;
747 spin_lock_irqsave(&logbuf_lock
, flags
);
748 wake_klogd
|= log_start
- log_end
;
749 if (con_start
== log_end
)
750 break; /* Nothing to print */
751 _con_start
= con_start
;
753 con_start
= log_end
; /* Flush */
754 spin_unlock(&logbuf_lock
);
755 call_console_drivers(_con_start
, _log_end
);
756 local_irq_restore(flags
);
759 console_may_schedule
= 0;
761 spin_unlock_irqrestore(&logbuf_lock
, flags
);
762 if (wake_klogd
&& !oops_in_progress
&& waitqueue_active(&log_wait
))
763 wake_up_interruptible(&log_wait
);
765 EXPORT_SYMBOL(release_console_sem
);
767 /** console_conditional_schedule - yield the CPU if required
769 * If the console code is currently allowed to sleep, and
770 * if this CPU should yield the CPU to another task, do
773 * Must be called within acquire_console_sem().
775 void __sched
console_conditional_schedule(void)
777 if (console_may_schedule
)
780 EXPORT_SYMBOL(console_conditional_schedule
);
782 void console_print(const char *s
)
784 printk(KERN_EMERG
"%s", s
);
786 EXPORT_SYMBOL(console_print
);
788 void console_unblank(void)
793 * console_unblank can no longer be called in interrupt context unless
794 * oops_in_progress is set to 1..
796 if (oops_in_progress
) {
797 if (down_trylock(&console_sem
) != 0)
800 acquire_console_sem();
803 console_may_schedule
= 0;
804 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
)
805 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
807 release_console_sem();
811 * Return the console tty driver structure and its associated index
813 struct tty_driver
*console_device(int *index
)
816 struct tty_driver
*driver
= NULL
;
818 acquire_console_sem();
819 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
) {
822 driver
= c
->device(c
, index
);
826 release_console_sem();
831 * Prevent further output on the passed console device so that (for example)
832 * serial drivers can disable console output before suspending a port, and can
833 * re-enable output afterwards.
835 void console_stop(struct console
*console
)
837 acquire_console_sem();
838 console
->flags
&= ~CON_ENABLED
;
839 release_console_sem();
841 EXPORT_SYMBOL(console_stop
);
843 void console_start(struct console
*console
)
845 acquire_console_sem();
846 console
->flags
|= CON_ENABLED
;
847 release_console_sem();
849 EXPORT_SYMBOL(console_start
);
852 * The console driver calls this routine during kernel initialization
853 * to register the console printing procedure with printk() and to
854 * print any messages that were printed by the kernel before the
855 * console driver was initialized.
857 void register_console(struct console
*console
)
862 if (preferred_console
< 0)
863 preferred_console
= selected_console
;
866 * See if we want to use this console driver. If we
867 * didn't select a console we take the first one
868 * that registers here.
870 if (preferred_console
< 0) {
871 if (console
->index
< 0)
873 if (console
->setup
== NULL
||
874 console
->setup(console
, NULL
) == 0) {
875 console
->flags
|= CON_ENABLED
| CON_CONSDEV
;
876 preferred_console
= 0;
881 * See if this console matches one we selected on
884 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
886 if (strcmp(console_cmdline
[i
].name
, console
->name
) != 0)
888 if (console
->index
>= 0 &&
889 console
->index
!= console_cmdline
[i
].index
)
891 if (console
->index
< 0)
892 console
->index
= console_cmdline
[i
].index
;
893 if (console
->setup
&&
894 console
->setup(console
, console_cmdline
[i
].options
) != 0)
896 console
->flags
|= CON_ENABLED
;
897 console
->index
= console_cmdline
[i
].index
;
898 if (i
== selected_console
) {
899 console
->flags
|= CON_CONSDEV
;
900 preferred_console
= selected_console
;
905 if (!(console
->flags
& CON_ENABLED
))
908 if (console_drivers
&& (console_drivers
->flags
& CON_BOOT
)) {
909 unregister_console(console_drivers
);
910 console
->flags
&= ~CON_PRINTBUFFER
;
914 * Put this console in the list - keep the
915 * preferred driver at the head of the list.
917 acquire_console_sem();
918 if ((console
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
919 console
->next
= console_drivers
;
920 console_drivers
= console
;
922 console
->next
->flags
&= ~CON_CONSDEV
;
924 console
->next
= console_drivers
->next
;
925 console_drivers
->next
= console
;
927 if (console
->flags
& CON_PRINTBUFFER
) {
929 * release_console_sem() will print out the buffered messages
932 spin_lock_irqsave(&logbuf_lock
, flags
);
933 con_start
= log_start
;
934 spin_unlock_irqrestore(&logbuf_lock
, flags
);
936 release_console_sem();
938 EXPORT_SYMBOL(register_console
);
940 int unregister_console(struct console
*console
)
942 struct console
*a
, *b
;
945 acquire_console_sem();
946 if (console_drivers
== console
) {
947 console_drivers
=console
->next
;
950 for (a
=console_drivers
->next
, b
=console_drivers
;
960 /* If last console is removed, we re-enable picking the first
961 * one that gets registered. Without that, pmac early boot console
962 * would prevent fbcon from taking over.
964 * If this isn't the last console and it has CON_CONSDEV set, we
965 * need to set it on the next preferred console.
967 if (console_drivers
== NULL
)
968 preferred_console
= selected_console
;
969 else if (console
->flags
& CON_CONSDEV
)
970 console_drivers
->flags
|= CON_CONSDEV
;
972 release_console_sem();
975 EXPORT_SYMBOL(unregister_console
);
978 * tty_write_message - write a message to a certain tty, not just the console.
980 * This is used for messages that need to be redirected to a specific tty.
981 * We don't put it into the syslog queue right now maybe in the future if
984 void tty_write_message(struct tty_struct
*tty
, char *msg
)
986 if (tty
&& tty
->driver
->write
)
987 tty
->driver
->write(tty
, msg
, strlen(msg
));
992 * printk rate limiting, lifted from the networking subsystem.
994 * This enforces a rate limit: not more than one kernel message
995 * every printk_ratelimit_jiffies to make a denial-of-service
998 int __printk_ratelimit(int ratelimit_jiffies
, int ratelimit_burst
)
1000 static DEFINE_SPINLOCK(ratelimit_lock
);
1001 static unsigned long toks
= 10 * 5 * HZ
;
1002 static unsigned long last_msg
;
1004 unsigned long flags
;
1005 unsigned long now
= jiffies
;
1007 spin_lock_irqsave(&ratelimit_lock
, flags
);
1008 toks
+= now
- last_msg
;
1010 if (toks
> (ratelimit_burst
* ratelimit_jiffies
))
1011 toks
= ratelimit_burst
* ratelimit_jiffies
;
1012 if (toks
>= ratelimit_jiffies
) {
1016 toks
-= ratelimit_jiffies
;
1017 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1019 printk(KERN_WARNING
"printk: %d messages suppressed.\n", lost
);
1023 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1026 EXPORT_SYMBOL(__printk_ratelimit
);
1028 /* minimum time in jiffies between messages */
1029 int printk_ratelimit_jiffies
= 5 * HZ
;
1031 /* number of messages we send before ratelimiting */
1032 int printk_ratelimit_burst
= 10;
1034 int printk_ratelimit(void)
1036 return __printk_ratelimit(printk_ratelimit_jiffies
,
1037 printk_ratelimit_burst
);
1039 EXPORT_SYMBOL(printk_ratelimit
);