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>
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;
442 module_param(printk_time
, int, S_IRUGO
| S_IWUSR
);
444 static int __init
printk_time_setup(char *str
)
452 __setup("time", printk_time_setup
);
454 __attribute__((weak
)) unsigned long long printk_clock(void)
456 return sched_clock();
459 /* Check if we have any console registered that can be called early in boot. */
460 static int have_callable_console(void)
464 for (con
= console_drivers
; con
; con
= con
->next
)
465 if (con
->flags
& CON_ANYTIME
)
472 * printk - print a kernel message
473 * @fmt: format string
475 * This is printk. It can be called from any context. We want it to work.
477 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
478 * call the console drivers. If we fail to get the semaphore we place the output
479 * into the log buffer and return. The current holder of the console_sem will
480 * notice the new output in release_console_sem() and will send it to the
481 * consoles before releasing the semaphore.
483 * One effect of this deferred printing is that code which calls printk() and
484 * then changes console_loglevel may break. This is because console_loglevel
485 * is inspected when the actual printing occurs.
491 asmlinkage
int printk(const char *fmt
, ...)
497 r
= vprintk(fmt
, args
);
503 /* cpu currently holding logbuf_lock */
504 static volatile unsigned int printk_cpu
= UINT_MAX
;
506 asmlinkage
int vprintk(const char *fmt
, va_list args
)
511 static char printk_buf
[1024];
512 static int log_level_unknown
= 1;
515 if (unlikely(oops_in_progress
) && printk_cpu
== smp_processor_id())
516 /* If a crash is occurring during printk() on this CPU,
517 * make sure we can't deadlock */
520 /* This stops the holder of console_sem just where we want him */
521 spin_lock_irqsave(&logbuf_lock
, flags
);
522 printk_cpu
= smp_processor_id();
524 /* Emit the output into the temporary buffer */
525 printed_len
= vscnprintf(printk_buf
, sizeof(printk_buf
), fmt
, args
);
528 * Copy the output into log_buf. If the caller didn't provide
529 * appropriate log level tags, we insert them here
531 for (p
= printk_buf
; *p
; p
++) {
532 if (log_level_unknown
) {
533 /* log_level_unknown signals the start of a new line */
538 unsigned long long t
;
539 unsigned long nanosec_rem
;
542 * force the log level token to be
543 * before the time output.
545 if (p
[0] == '<' && p
[1] >='0' &&
546 p
[1] <= '7' && p
[2] == '>') {
551 loglev_char
= default_message_loglevel
555 nanosec_rem
= do_div(t
, 1000000000);
562 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
566 if (p
[0] != '<' || p
[1] < '0' ||
567 p
[1] > '7' || p
[2] != '>') {
569 emit_log_char(default_message_loglevel
575 log_level_unknown
= 0;
581 log_level_unknown
= 1;
584 if (!down_trylock(&console_sem
)) {
586 * We own the drivers. We can drop the spinlock and
587 * let release_console_sem() print the text, maybe ...
590 printk_cpu
= UINT_MAX
;
591 spin_unlock_irqrestore(&logbuf_lock
, flags
);
594 * Console drivers may assume that per-cpu resources have
595 * been allocated. So unless they're explicitly marked as
596 * being able to cope (CON_ANYTIME) don't call them until
597 * this CPU is officially up.
599 if (cpu_online(smp_processor_id()) || have_callable_console()) {
600 console_may_schedule
= 0;
601 release_console_sem();
603 /* Release by hand to avoid flushing the buffer. */
609 * Someone else owns the drivers. We drop the spinlock, which
610 * allows the semaphore holder to proceed and to call the
611 * console drivers with the output which we just produced.
613 printk_cpu
= UINT_MAX
;
614 spin_unlock_irqrestore(&logbuf_lock
, flags
);
620 EXPORT_SYMBOL(printk
);
621 EXPORT_SYMBOL(vprintk
);
625 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
630 int do_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
;
719 * suspend_console - suspend the console subsystem
721 * This disables printk() while we go into suspend states
723 void suspend_console(void)
725 acquire_console_sem();
726 console_suspended
= 1;
729 void resume_console(void)
731 console_suspended
= 0;
732 release_console_sem();
736 * acquire_console_sem - lock the console system for exclusive use.
738 * Acquires a semaphore which guarantees that the caller has
739 * exclusive access to the console system and the console_drivers list.
741 * Can sleep, returns nothing.
743 void acquire_console_sem(void)
745 BUG_ON(in_interrupt());
746 if (console_suspended
) {
747 down(&secondary_console_sem
);
752 console_may_schedule
= 1;
754 EXPORT_SYMBOL(acquire_console_sem
);
756 int try_acquire_console_sem(void)
758 if (down_trylock(&console_sem
))
761 console_may_schedule
= 0;
764 EXPORT_SYMBOL(try_acquire_console_sem
);
766 int is_console_locked(void)
768 return console_locked
;
770 EXPORT_SYMBOL(is_console_locked
);
773 * release_console_sem - unlock the console system
775 * Releases the semaphore which the caller holds on the console system
776 * and the console driver list.
778 * While the semaphore was held, console output may have been buffered
779 * by printk(). If this is the case, release_console_sem() emits
780 * the output prior to releasing the semaphore.
782 * If there is output waiting for klogd, we wake it up.
784 * release_console_sem() may be called from any context.
786 void release_console_sem(void)
789 unsigned long _con_start
, _log_end
;
790 unsigned long wake_klogd
= 0;
792 if (console_suspended
) {
793 up(&secondary_console_sem
);
797 spin_lock_irqsave(&logbuf_lock
, flags
);
798 wake_klogd
|= log_start
- log_end
;
799 if (con_start
== log_end
)
800 break; /* Nothing to print */
801 _con_start
= con_start
;
803 con_start
= log_end
; /* Flush */
804 spin_unlock(&logbuf_lock
);
805 call_console_drivers(_con_start
, _log_end
);
806 local_irq_restore(flags
);
809 console_may_schedule
= 0;
811 spin_unlock_irqrestore(&logbuf_lock
, flags
);
812 if (wake_klogd
&& !oops_in_progress
&& waitqueue_active(&log_wait
))
813 wake_up_interruptible(&log_wait
);
815 EXPORT_SYMBOL(release_console_sem
);
818 * console_conditional_schedule - yield the CPU if required
820 * If the console code is currently allowed to sleep, and
821 * if this CPU should yield the CPU to another task, do
824 * Must be called within acquire_console_sem().
826 void __sched
console_conditional_schedule(void)
828 if (console_may_schedule
)
831 EXPORT_SYMBOL(console_conditional_schedule
);
833 void console_print(const char *s
)
835 printk(KERN_EMERG
"%s", s
);
837 EXPORT_SYMBOL(console_print
);
839 void console_unblank(void)
844 * console_unblank can no longer be called in interrupt context unless
845 * oops_in_progress is set to 1..
847 if (oops_in_progress
) {
848 if (down_trylock(&console_sem
) != 0)
851 acquire_console_sem();
854 console_may_schedule
= 0;
855 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
)
856 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
858 release_console_sem();
862 * Return the console tty driver structure and its associated index
864 struct tty_driver
*console_device(int *index
)
867 struct tty_driver
*driver
= NULL
;
869 acquire_console_sem();
870 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
) {
873 driver
= c
->device(c
, index
);
877 release_console_sem();
882 * Prevent further output on the passed console device so that (for example)
883 * serial drivers can disable console output before suspending a port, and can
884 * re-enable output afterwards.
886 void console_stop(struct console
*console
)
888 acquire_console_sem();
889 console
->flags
&= ~CON_ENABLED
;
890 release_console_sem();
892 EXPORT_SYMBOL(console_stop
);
894 void console_start(struct console
*console
)
896 acquire_console_sem();
897 console
->flags
|= CON_ENABLED
;
898 release_console_sem();
900 EXPORT_SYMBOL(console_start
);
903 * The console driver calls this routine during kernel initialization
904 * to register the console printing procedure with printk() and to
905 * print any messages that were printed by the kernel before the
906 * console driver was initialized.
908 void register_console(struct console
*console
)
913 if (preferred_console
< 0)
914 preferred_console
= selected_console
;
917 * See if we want to use this console driver. If we
918 * didn't select a console we take the first one
919 * that registers here.
921 if (preferred_console
< 0) {
922 if (console
->index
< 0)
924 if (console
->setup
== NULL
||
925 console
->setup(console
, NULL
) == 0) {
926 console
->flags
|= CON_ENABLED
| CON_CONSDEV
;
927 preferred_console
= 0;
932 * See if this console matches one we selected on
935 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
937 if (strcmp(console_cmdline
[i
].name
, console
->name
) != 0)
939 if (console
->index
>= 0 &&
940 console
->index
!= console_cmdline
[i
].index
)
942 if (console
->index
< 0)
943 console
->index
= console_cmdline
[i
].index
;
944 if (console
->setup
&&
945 console
->setup(console
, console_cmdline
[i
].options
) != 0)
947 console
->flags
|= CON_ENABLED
;
948 console
->index
= console_cmdline
[i
].index
;
949 if (i
== selected_console
) {
950 console
->flags
|= CON_CONSDEV
;
951 preferred_console
= selected_console
;
956 if (!(console
->flags
& CON_ENABLED
))
959 if (console_drivers
&& (console_drivers
->flags
& CON_BOOT
)) {
960 unregister_console(console_drivers
);
961 console
->flags
&= ~CON_PRINTBUFFER
;
965 * Put this console in the list - keep the
966 * preferred driver at the head of the list.
968 acquire_console_sem();
969 if ((console
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
970 console
->next
= console_drivers
;
971 console_drivers
= console
;
973 console
->next
->flags
&= ~CON_CONSDEV
;
975 console
->next
= console_drivers
->next
;
976 console_drivers
->next
= console
;
978 if (console
->flags
& CON_PRINTBUFFER
) {
980 * release_console_sem() will print out the buffered messages
983 spin_lock_irqsave(&logbuf_lock
, flags
);
984 con_start
= log_start
;
985 spin_unlock_irqrestore(&logbuf_lock
, flags
);
987 release_console_sem();
989 EXPORT_SYMBOL(register_console
);
991 int unregister_console(struct console
*console
)
993 struct console
*a
, *b
;
996 acquire_console_sem();
997 if (console_drivers
== console
) {
998 console_drivers
=console
->next
;
1000 } else if (console_drivers
) {
1001 for (a
=console_drivers
->next
, b
=console_drivers
;
1002 a
; b
=a
, a
=b
->next
) {
1011 /* If last console is removed, we re-enable picking the first
1012 * one that gets registered. Without that, pmac early boot console
1013 * would prevent fbcon from taking over.
1015 * If this isn't the last console and it has CON_CONSDEV set, we
1016 * need to set it on the next preferred console.
1018 if (console_drivers
== NULL
)
1019 preferred_console
= selected_console
;
1020 else if (console
->flags
& CON_CONSDEV
)
1021 console_drivers
->flags
|= CON_CONSDEV
;
1023 release_console_sem();
1026 EXPORT_SYMBOL(unregister_console
);
1029 * tty_write_message - write a message to a certain tty, not just the console.
1030 * @tty: the destination tty_struct
1031 * @msg: the message to write
1033 * This is used for messages that need to be redirected to a specific tty.
1034 * We don't put it into the syslog queue right now maybe in the future if
1037 void tty_write_message(struct tty_struct
*tty
, char *msg
)
1039 if (tty
&& tty
->driver
->write
)
1040 tty
->driver
->write(tty
, msg
, strlen(msg
));
1045 * printk rate limiting, lifted from the networking subsystem.
1047 * This enforces a rate limit: not more than one kernel message
1048 * every printk_ratelimit_jiffies to make a denial-of-service
1049 * attack impossible.
1051 int __printk_ratelimit(int ratelimit_jiffies
, int ratelimit_burst
)
1053 static DEFINE_SPINLOCK(ratelimit_lock
);
1054 static unsigned long toks
= 10 * 5 * HZ
;
1055 static unsigned long last_msg
;
1057 unsigned long flags
;
1058 unsigned long now
= jiffies
;
1060 spin_lock_irqsave(&ratelimit_lock
, flags
);
1061 toks
+= now
- last_msg
;
1063 if (toks
> (ratelimit_burst
* ratelimit_jiffies
))
1064 toks
= ratelimit_burst
* ratelimit_jiffies
;
1065 if (toks
>= ratelimit_jiffies
) {
1069 toks
-= ratelimit_jiffies
;
1070 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1072 printk(KERN_WARNING
"printk: %d messages suppressed.\n", lost
);
1076 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1079 EXPORT_SYMBOL(__printk_ratelimit
);
1081 /* minimum time in jiffies between messages */
1082 int printk_ratelimit_jiffies
= 5 * HZ
;
1084 /* number of messages we send before ratelimiting */
1085 int printk_ratelimit_burst
= 10;
1087 int printk_ratelimit(void)
1089 return __printk_ratelimit(printk_ratelimit_jiffies
,
1090 printk_ratelimit_burst
);
1092 EXPORT_SYMBOL(printk_ratelimit
);