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/moduleparam.h>
28 #include <linux/interrupt.h> /* For in_interrupt() */
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>
34 #include <linux/jiffies.h>
36 #include <asm/uaccess.h>
38 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
40 /* printk's without a loglevel use this.. */
41 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
43 /* We show everything that is MORE important than this.. */
44 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
45 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
47 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
49 int console_printk
[4] = {
50 DEFAULT_CONSOLE_LOGLEVEL
, /* console_loglevel */
51 DEFAULT_MESSAGE_LOGLEVEL
, /* default_message_loglevel */
52 MINIMUM_CONSOLE_LOGLEVEL
, /* minimum_console_loglevel */
53 DEFAULT_CONSOLE_LOGLEVEL
, /* default_console_loglevel */
57 * Low lever drivers may need that to know if they can schedule in
58 * their unblank() callback or not. So let's export it.
61 EXPORT_SYMBOL(oops_in_progress
);
64 * console_sem protects the console_drivers list, and also
65 * provides serialisation for access to the entire console
68 static DECLARE_MUTEX(console_sem
);
69 static DECLARE_MUTEX(secondary_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
, console_suspended
;
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 (cpu_online(smp_processor_id()) ||
331 (con
->flags
& CON_ANYTIME
)))
332 con
->write(con
, &LOG_BUF(start
), end
- start
);
337 * Write out chars from start to end - 1 inclusive
339 static void _call_console_drivers(unsigned long start
,
340 unsigned long end
, int msg_log_level
)
342 if (msg_log_level
< console_loglevel
&&
343 console_drivers
&& start
!= end
) {
344 if ((start
& LOG_BUF_MASK
) > (end
& LOG_BUF_MASK
)) {
346 __call_console_drivers(start
& LOG_BUF_MASK
,
348 __call_console_drivers(0, end
& LOG_BUF_MASK
);
350 __call_console_drivers(start
, end
);
356 * Call the console drivers, asking them to write out
357 * log_buf[start] to log_buf[end - 1].
358 * The console_sem must be held.
360 static void call_console_drivers(unsigned long start
, unsigned long end
)
362 unsigned long cur_index
, start_print
;
363 static int msg_level
= -1;
365 BUG_ON(((long)(start
- end
)) > 0);
369 while (cur_index
!= end
) {
370 if (msg_level
< 0 && ((end
- cur_index
) > 2) &&
371 LOG_BUF(cur_index
+ 0) == '<' &&
372 LOG_BUF(cur_index
+ 1) >= '0' &&
373 LOG_BUF(cur_index
+ 1) <= '7' &&
374 LOG_BUF(cur_index
+ 2) == '>') {
375 msg_level
= LOG_BUF(cur_index
+ 1) - '0';
377 start_print
= cur_index
;
379 while (cur_index
!= end
) {
380 char c
= LOG_BUF(cur_index
);
386 * printk() has already given us loglevel tags in
387 * the buffer. This code is here in case the
388 * log buffer has wrapped right round and scribbled
391 msg_level
= default_message_loglevel
;
393 _call_console_drivers(start_print
, cur_index
, msg_level
);
395 start_print
= cur_index
;
400 _call_console_drivers(start_print
, end
, msg_level
);
403 static void emit_log_char(char c
)
405 LOG_BUF(log_end
) = c
;
407 if (log_end
- log_start
> log_buf_len
)
408 log_start
= log_end
- log_buf_len
;
409 if (log_end
- con_start
> log_buf_len
)
410 con_start
= log_end
- log_buf_len
;
411 if (logged_chars
< log_buf_len
)
416 * Zap console related locks when oopsing. Only zap at most once
417 * every 10 seconds, to leave time for slow consoles to print a
420 static void zap_locks(void)
422 static unsigned long oops_timestamp
;
424 if (time_after_eq(jiffies
, oops_timestamp
) &&
425 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
428 oops_timestamp
= jiffies
;
430 /* If a crash is occurring, make sure we can't deadlock */
431 spin_lock_init(&logbuf_lock
);
432 /* And make sure that we print immediately */
433 init_MUTEX(&console_sem
);
436 #if defined(CONFIG_PRINTK_TIME)
437 static int printk_time
= 1;
439 static int printk_time
= 0;
441 module_param(printk_time
, int, S_IRUGO
| S_IWUSR
);
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 local_irq_save(flags
);
522 spin_lock(&logbuf_lock
);
523 printk_cpu
= smp_processor_id();
525 /* Emit the output into the temporary buffer */
526 printed_len
= vscnprintf(printk_buf
, sizeof(printk_buf
), fmt
, args
);
529 * Copy the output into log_buf. If the caller didn't provide
530 * appropriate log level tags, we insert them here
532 for (p
= printk_buf
; *p
; p
++) {
533 if (log_level_unknown
) {
534 /* log_level_unknown signals the start of a new line */
539 unsigned long long t
;
540 unsigned long nanosec_rem
;
543 * force the log level token to be
544 * before the time output.
546 if (p
[0] == '<' && p
[1] >='0' &&
547 p
[1] <= '7' && p
[2] == '>') {
552 loglev_char
= default_message_loglevel
556 nanosec_rem
= do_div(t
, 1000000000);
563 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
567 if (p
[0] != '<' || p
[1] < '0' ||
568 p
[1] > '7' || p
[2] != '>') {
570 emit_log_char(default_message_loglevel
576 log_level_unknown
= 0;
582 log_level_unknown
= 1;
585 if (!down_trylock(&console_sem
)) {
587 * We own the drivers. We can drop the spinlock and
588 * let release_console_sem() print the text, maybe ...
591 printk_cpu
= UINT_MAX
;
592 spin_unlock(&logbuf_lock
);
595 * Console drivers may assume that per-cpu resources have
596 * been allocated. So unless they're explicitly marked as
597 * being able to cope (CON_ANYTIME) don't call them until
598 * this CPU is officially up.
600 if (cpu_online(smp_processor_id()) || have_callable_console()) {
601 console_may_schedule
= 0;
602 release_console_sem();
604 /* Release by hand to avoid flushing the buffer. */
609 local_irq_restore(flags
);
612 * Someone else owns the drivers. We drop the spinlock, which
613 * allows the semaphore holder to proceed and to call the
614 * console drivers with the output which we just produced.
616 printk_cpu
= UINT_MAX
;
617 spin_unlock(&logbuf_lock
);
619 local_irq_restore(flags
);
625 EXPORT_SYMBOL(printk
);
626 EXPORT_SYMBOL(vprintk
);
630 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
635 static void call_console_drivers(unsigned long start
, unsigned long end
)
642 * Set up a list of consoles. Called from init/main.c
644 static int __init
console_setup(char *str
)
646 char name
[sizeof(console_cmdline
[0].name
)];
651 * Decode str into name, index, options.
653 if (str
[0] >= '0' && str
[0] <= '9') {
654 strcpy(name
, "ttyS");
655 strncpy(name
+ 4, str
, sizeof(name
) - 5);
657 strncpy(name
, str
, sizeof(name
) - 1);
659 name
[sizeof(name
) - 1] = 0;
660 if ((options
= strchr(str
, ',')) != NULL
)
663 if (!strcmp(str
, "ttya"))
664 strcpy(name
, "ttyS0");
665 if (!strcmp(str
, "ttyb"))
666 strcpy(name
, "ttyS1");
668 for (s
= name
; *s
; s
++)
669 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
671 idx
= simple_strtoul(s
, NULL
, 10);
674 add_preferred_console(name
, idx
, options
);
677 __setup("console=", console_setup
);
680 * add_preferred_console - add a device to the list of preferred consoles.
683 * @options: options for this console
685 * The last preferred console added will be used for kernel messages
686 * and stdin/out/err for init. Normally this is used by console_setup
687 * above to handle user-supplied console arguments; however it can also
688 * be used by arch-specific code either to override the user or more
689 * commonly to provide a default console (ie from PROM variables) when
690 * the user has not supplied one.
692 int __init
add_preferred_console(char *name
, int idx
, char *options
)
694 struct console_cmdline
*c
;
698 * See if this tty is not yet registered, and
699 * if we have a slot free.
701 for(i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
702 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
703 console_cmdline
[i
].index
== idx
) {
704 selected_console
= i
;
707 if (i
== MAX_CMDLINECONSOLES
)
709 selected_console
= i
;
710 c
= &console_cmdline
[i
];
711 memcpy(c
->name
, name
, sizeof(c
->name
));
712 c
->name
[sizeof(c
->name
) - 1] = 0;
713 c
->options
= options
;
718 #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
720 * suspend_console - suspend the console subsystem
722 * This disables printk() while we go into suspend states
724 void suspend_console(void)
726 printk("Suspending console(s)\n");
727 acquire_console_sem();
728 console_suspended
= 1;
731 void resume_console(void)
733 console_suspended
= 0;
734 release_console_sem();
736 #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
739 * acquire_console_sem - lock the console system for exclusive use.
741 * Acquires a semaphore which guarantees that the caller has
742 * exclusive access to the console system and the console_drivers list.
744 * Can sleep, returns nothing.
746 void acquire_console_sem(void)
748 BUG_ON(in_interrupt());
749 if (console_suspended
) {
750 down(&secondary_console_sem
);
755 console_may_schedule
= 1;
757 EXPORT_SYMBOL(acquire_console_sem
);
759 int try_acquire_console_sem(void)
761 if (down_trylock(&console_sem
))
764 console_may_schedule
= 0;
767 EXPORT_SYMBOL(try_acquire_console_sem
);
769 int is_console_locked(void)
771 return console_locked
;
775 * release_console_sem - unlock the console system
777 * Releases the semaphore which the caller holds on the console system
778 * and the console driver list.
780 * While the semaphore was held, console output may have been buffered
781 * by printk(). If this is the case, release_console_sem() emits
782 * the output prior to releasing the semaphore.
784 * If there is output waiting for klogd, we wake it up.
786 * release_console_sem() may be called from any context.
788 void release_console_sem(void)
791 unsigned long _con_start
, _log_end
;
792 unsigned long wake_klogd
= 0;
794 if (console_suspended
) {
795 up(&secondary_console_sem
);
799 console_may_schedule
= 0;
802 spin_lock_irqsave(&logbuf_lock
, flags
);
803 wake_klogd
|= log_start
- log_end
;
804 if (con_start
== log_end
)
805 break; /* Nothing to print */
806 _con_start
= con_start
;
808 con_start
= log_end
; /* Flush */
809 spin_unlock(&logbuf_lock
);
810 call_console_drivers(_con_start
, _log_end
);
811 local_irq_restore(flags
);
815 spin_unlock_irqrestore(&logbuf_lock
, flags
);
816 if (wake_klogd
&& !oops_in_progress
&& waitqueue_active(&log_wait
))
817 wake_up_interruptible(&log_wait
);
819 EXPORT_SYMBOL(release_console_sem
);
822 * console_conditional_schedule - yield the CPU if required
824 * If the console code is currently allowed to sleep, and
825 * if this CPU should yield the CPU to another task, do
828 * Must be called within acquire_console_sem().
830 void __sched
console_conditional_schedule(void)
832 if (console_may_schedule
)
835 EXPORT_SYMBOL(console_conditional_schedule
);
837 void console_print(const char *s
)
839 printk(KERN_EMERG
"%s", s
);
841 EXPORT_SYMBOL(console_print
);
843 void console_unblank(void)
848 * console_unblank can no longer be called in interrupt context unless
849 * oops_in_progress is set to 1..
851 if (oops_in_progress
) {
852 if (down_trylock(&console_sem
) != 0)
855 acquire_console_sem();
858 console_may_schedule
= 0;
859 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
)
860 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
862 release_console_sem();
866 * Return the console tty driver structure and its associated index
868 struct tty_driver
*console_device(int *index
)
871 struct tty_driver
*driver
= NULL
;
873 acquire_console_sem();
874 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
) {
877 driver
= c
->device(c
, index
);
881 release_console_sem();
886 * Prevent further output on the passed console device so that (for example)
887 * serial drivers can disable console output before suspending a port, and can
888 * re-enable output afterwards.
890 void console_stop(struct console
*console
)
892 acquire_console_sem();
893 console
->flags
&= ~CON_ENABLED
;
894 release_console_sem();
896 EXPORT_SYMBOL(console_stop
);
898 void console_start(struct console
*console
)
900 acquire_console_sem();
901 console
->flags
|= CON_ENABLED
;
902 release_console_sem();
904 EXPORT_SYMBOL(console_start
);
907 * The console driver calls this routine during kernel initialization
908 * to register the console printing procedure with printk() and to
909 * print any messages that were printed by the kernel before the
910 * console driver was initialized.
912 void register_console(struct console
*console
)
917 if (preferred_console
< 0)
918 preferred_console
= selected_console
;
921 * See if we want to use this console driver. If we
922 * didn't select a console we take the first one
923 * that registers here.
925 if (preferred_console
< 0) {
926 if (console
->index
< 0)
928 if (console
->setup
== NULL
||
929 console
->setup(console
, NULL
) == 0) {
930 console
->flags
|= CON_ENABLED
| CON_CONSDEV
;
931 preferred_console
= 0;
936 * See if this console matches one we selected on
939 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
941 if (strcmp(console_cmdline
[i
].name
, console
->name
) != 0)
943 if (console
->index
>= 0 &&
944 console
->index
!= console_cmdline
[i
].index
)
946 if (console
->index
< 0)
947 console
->index
= console_cmdline
[i
].index
;
948 if (console
->setup
&&
949 console
->setup(console
, console_cmdline
[i
].options
) != 0)
951 console
->flags
|= CON_ENABLED
;
952 console
->index
= console_cmdline
[i
].index
;
953 if (i
== selected_console
) {
954 console
->flags
|= CON_CONSDEV
;
955 preferred_console
= selected_console
;
960 if (!(console
->flags
& CON_ENABLED
))
963 if (console_drivers
&& (console_drivers
->flags
& CON_BOOT
)) {
964 unregister_console(console_drivers
);
965 console
->flags
&= ~CON_PRINTBUFFER
;
969 * Put this console in the list - keep the
970 * preferred driver at the head of the list.
972 acquire_console_sem();
973 if ((console
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
974 console
->next
= console_drivers
;
975 console_drivers
= console
;
977 console
->next
->flags
&= ~CON_CONSDEV
;
979 console
->next
= console_drivers
->next
;
980 console_drivers
->next
= console
;
982 if (console
->flags
& CON_PRINTBUFFER
) {
984 * release_console_sem() will print out the buffered messages
987 spin_lock_irqsave(&logbuf_lock
, flags
);
988 con_start
= log_start
;
989 spin_unlock_irqrestore(&logbuf_lock
, flags
);
991 release_console_sem();
993 EXPORT_SYMBOL(register_console
);
995 int unregister_console(struct console
*console
)
997 struct console
*a
, *b
;
1000 acquire_console_sem();
1001 if (console_drivers
== console
) {
1002 console_drivers
=console
->next
;
1004 } else if (console_drivers
) {
1005 for (a
=console_drivers
->next
, b
=console_drivers
;
1006 a
; b
=a
, a
=b
->next
) {
1015 /* If last console is removed, we re-enable picking the first
1016 * one that gets registered. Without that, pmac early boot console
1017 * would prevent fbcon from taking over.
1019 * If this isn't the last console and it has CON_CONSDEV set, we
1020 * need to set it on the next preferred console.
1022 if (console_drivers
== NULL
)
1023 preferred_console
= selected_console
;
1024 else if (console
->flags
& CON_CONSDEV
)
1025 console_drivers
->flags
|= CON_CONSDEV
;
1027 release_console_sem();
1030 EXPORT_SYMBOL(unregister_console
);
1033 * tty_write_message - write a message to a certain tty, not just the console.
1034 * @tty: the destination tty_struct
1035 * @msg: the message to write
1037 * This is used for messages that need to be redirected to a specific tty.
1038 * We don't put it into the syslog queue right now maybe in the future if
1041 void tty_write_message(struct tty_struct
*tty
, char *msg
)
1043 if (tty
&& tty
->driver
->write
)
1044 tty
->driver
->write(tty
, msg
, strlen(msg
));
1049 * printk rate limiting, lifted from the networking subsystem.
1051 * This enforces a rate limit: not more than one kernel message
1052 * every printk_ratelimit_jiffies to make a denial-of-service
1053 * attack impossible.
1055 int __printk_ratelimit(int ratelimit_jiffies
, int ratelimit_burst
)
1057 static DEFINE_SPINLOCK(ratelimit_lock
);
1058 static unsigned long toks
= 10 * 5 * HZ
;
1059 static unsigned long last_msg
;
1061 unsigned long flags
;
1062 unsigned long now
= jiffies
;
1064 spin_lock_irqsave(&ratelimit_lock
, flags
);
1065 toks
+= now
- last_msg
;
1067 if (toks
> (ratelimit_burst
* ratelimit_jiffies
))
1068 toks
= ratelimit_burst
* ratelimit_jiffies
;
1069 if (toks
>= ratelimit_jiffies
) {
1073 toks
-= ratelimit_jiffies
;
1074 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1076 printk(KERN_WARNING
"printk: %d messages suppressed.\n", lost
);
1080 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1083 EXPORT_SYMBOL(__printk_ratelimit
);
1085 /* minimum time in jiffies between messages */
1086 int printk_ratelimit_jiffies
= 5 * HZ
;
1088 /* number of messages we send before ratelimiting */
1089 int printk_ratelimit_burst
= 10;
1091 int printk_ratelimit(void)
1093 return __printk_ratelimit(printk_ratelimit_jiffies
,
1094 printk_ratelimit_burst
);
1096 EXPORT_SYMBOL(printk_ratelimit
);
1099 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1100 * @caller_jiffies: pointer to caller's state
1101 * @interval_msecs: minimum interval between prints
1103 * printk_timed_ratelimit() returns true if more than @interval_msecs
1104 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1107 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
1108 unsigned int interval_msecs
)
1110 if (*caller_jiffies
== 0 || time_after(jiffies
, *caller_jiffies
)) {
1111 *caller_jiffies
= jiffies
+ msecs_to_jiffies(interval_msecs
);
1116 EXPORT_SYMBOL(printk_timed_ratelimit
);