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
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/syscalls.h>
36 #include <asm/uaccess.h>
39 * Architectures can override it:
41 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
45 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
47 #ifdef CONFIG_DEBUG_LL
48 extern void printascii(char *);
51 /* printk's without a loglevel use this.. */
52 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
54 /* We show everything that is MORE important than this.. */
55 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
56 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
58 DECLARE_WAIT_QUEUE_HEAD(log_wait);
60 int console_printk[4] = {
61 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
62 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
63 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
64 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
68 * Low level drivers may need that to know if they can schedule in
69 * their unblank() callback or not. So let's export it.
72 EXPORT_SYMBOL(oops_in_progress);
75 * console_sem protects the console_drivers list, and also
76 * provides serialisation for access to the entire console
79 static DECLARE_MUTEX(console_sem);
80 static DECLARE_MUTEX(secondary_console_sem);
81 struct console *console_drivers;
82 EXPORT_SYMBOL_GPL(console_drivers);
85 * This is used for debugging the mess that is the VT code by
86 * keeping track if we have the console semaphore held. It's
87 * definitely not the perfect debug tool (we don't know if _WE_
88 * hold it are racing, but it helps tracking those weird code
89 * path in the console code where we end up in places I want
90 * locked without the console sempahore held
92 static int console_locked, console_suspended;
95 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
96 * It is also used in interesting ways to provide interlocking in
97 * release_console_sem().
99 static DEFINE_SPINLOCK(logbuf_lock);
101 #define LOG_BUF_MASK (log_buf_len-1)
102 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
105 * The indices into log_buf are not constrained to log_buf_len - they
106 * must be masked before subscripting
108 static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
109 static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
110 static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
113 * Array of consoles built from command line options (console=)
115 struct console_cmdline
117 char name[8]; /* Name of the driver */
118 int index; /* Minor dev. to use */
119 char *options; /* Options for the driver */
120 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
121 char *brl_options; /* Options for braille driver */
125 #define MAX_CMDLINECONSOLES 8
127 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
128 static int selected_console = -1;
129 static int preferred_console = -1;
130 int console_set_on_cmdline;
131 EXPORT_SYMBOL(console_set_on_cmdline);
133 /* Flag: console code may call schedule() */
134 static int console_may_schedule;
138 static char __log_buf[__LOG_BUF_LEN];
139 static char *log_buf = __log_buf;
140 static int log_buf_len = __LOG_BUF_LEN;
141 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
143 static int __init log_buf_len_setup(char *str)
145 unsigned size = memparse(str, &str);
149 size = roundup_pow_of_two(size);
150 if (size > log_buf_len) {
151 unsigned start, dest_idx, offset;
154 new_log_buf = alloc_bootmem(size);
156 printk(KERN_WARNING "log_buf_len: allocation failed\n");
160 spin_lock_irqsave(&logbuf_lock, flags);
162 log_buf = new_log_buf;
164 offset = start = min(con_start, log_start);
166 while (start != log_end) {
167 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
174 spin_unlock_irqrestore(&logbuf_lock, flags);
176 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
182 __setup("log_buf_len=", log_buf_len_setup);
184 #ifdef CONFIG_BOOT_PRINTK_DELAY
186 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
187 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
189 static int __init boot_delay_setup(char *str)
192 unsigned long long loops_per_msec;
194 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
195 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
197 get_option(&str, &boot_delay);
198 if (boot_delay > 10 * 1000)
201 printk_delay_msec = loops_per_msec;
202 printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
203 "HZ: %d, printk_delay_msec: %llu\n",
204 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
207 __setup("boot_delay=", boot_delay_setup);
209 static void boot_delay_msec(void)
211 unsigned long long k;
212 unsigned long timeout;
214 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
217 k = (unsigned long long)printk_delay_msec * boot_delay;
219 timeout = jiffies + msecs_to_jiffies(boot_delay);
224 * use (volatile) jiffies to prevent
225 * compiler reduction; loop termination via jiffies
226 * is secondary and may or may not happen.
228 if (time_after(jiffies, timeout))
230 touch_nmi_watchdog();
234 static inline void boot_delay_msec(void)
240 * Commands to do_syslog:
242 * 0 -- Close the log. Currently a NOP.
243 * 1 -- Open the log. Currently a NOP.
244 * 2 -- Read from the log.
245 * 3 -- Read all messages remaining in the ring buffer.
246 * 4 -- Read and clear all messages remaining in the ring buffer
247 * 5 -- Clear ring buffer.
248 * 6 -- Disable printk's to console
249 * 7 -- Enable printk's to console
250 * 8 -- Set level of messages printed to console
251 * 9 -- Return number of unread characters in the log buffer
252 * 10 -- Return size of the log buffer
254 int do_syslog(int type, char __user *buf, int len)
256 unsigned i, j, limit, count;
261 error = security_syslog(type);
266 case 0: /* Close log */
268 case 1: /* Open log */
270 case 2: /* Read from log */
277 if (!access_ok(VERIFY_WRITE, buf, len)) {
281 error = wait_event_interruptible(log_wait,
282 (log_start - log_end));
286 spin_lock_irq(&logbuf_lock);
287 while (!error && (log_start != log_end) && i < len) {
288 c = LOG_BUF(log_start);
290 spin_unlock_irq(&logbuf_lock);
291 error = __put_user(c,buf);
295 spin_lock_irq(&logbuf_lock);
297 spin_unlock_irq(&logbuf_lock);
301 case 4: /* Read/clear last kernel messages */
304 case 3: /* Read last kernel messages */
311 if (!access_ok(VERIFY_WRITE, buf, len)) {
316 if (count > log_buf_len)
318 spin_lock_irq(&logbuf_lock);
319 if (count > logged_chars)
320 count = logged_chars;
325 * __put_user() could sleep, and while we sleep
326 * printk() could overwrite the messages
327 * we try to copy to user space. Therefore
328 * the messages are copied in reverse. <manfreds>
330 for (i = 0; i < count && !error; i++) {
332 if (j + log_buf_len < log_end)
335 spin_unlock_irq(&logbuf_lock);
336 error = __put_user(c,&buf[count-1-i]);
338 spin_lock_irq(&logbuf_lock);
340 spin_unlock_irq(&logbuf_lock);
345 int offset = count-error;
346 /* buffer overflow during copy, correct user buffer. */
347 for (i = 0; i < error; i++) {
348 if (__get_user(c,&buf[i+offset]) ||
349 __put_user(c,&buf[i])) {
357 case 5: /* Clear ring buffer */
360 case 6: /* Disable logging to console */
361 console_loglevel = minimum_console_loglevel;
363 case 7: /* Enable logging to console */
364 console_loglevel = default_console_loglevel;
366 case 8: /* Set level of messages printed to console */
368 if (len < 1 || len > 8)
370 if (len < minimum_console_loglevel)
371 len = minimum_console_loglevel;
372 console_loglevel = len;
375 case 9: /* Number of chars in the log buffer */
376 error = log_end - log_start;
378 case 10: /* Size of the log buffer */
389 asmlinkage long sys_syslog(int type, char __user *buf, int len)
391 return do_syslog(type, buf, len);
395 * Call the console drivers on a range of log_buf
397 static void __call_console_drivers(unsigned start, unsigned end)
401 for (con = console_drivers; con; con = con->next) {
402 if ((con->flags & CON_ENABLED) && con->write &&
403 (cpu_online(smp_processor_id()) ||
404 (con->flags & CON_ANYTIME)))
405 con->write(con, &LOG_BUF(start), end - start);
409 static int __read_mostly ignore_loglevel;
411 static int __init ignore_loglevel_setup(char *str)
414 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
419 early_param("ignore_loglevel", ignore_loglevel_setup);
422 * Write out chars from start to end - 1 inclusive
424 static void _call_console_drivers(unsigned start,
425 unsigned end, int msg_log_level)
427 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
428 console_drivers && start != end) {
429 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
431 __call_console_drivers(start & LOG_BUF_MASK,
433 __call_console_drivers(0, end & LOG_BUF_MASK);
435 __call_console_drivers(start, end);
441 * Call the console drivers, asking them to write out
442 * log_buf[start] to log_buf[end - 1].
443 * The console_sem must be held.
445 static void call_console_drivers(unsigned start, unsigned end)
447 unsigned cur_index, start_print;
448 static int msg_level = -1;
450 BUG_ON(((int)(start - end)) > 0);
454 while (cur_index != end) {
455 if (msg_level < 0 && ((end - cur_index) > 2) &&
456 LOG_BUF(cur_index + 0) == '<' &&
457 LOG_BUF(cur_index + 1) >= '0' &&
458 LOG_BUF(cur_index + 1) <= '7' &&
459 LOG_BUF(cur_index + 2) == '>') {
460 msg_level = LOG_BUF(cur_index + 1) - '0';
462 start_print = cur_index;
464 while (cur_index != end) {
465 char c = LOG_BUF(cur_index);
471 * printk() has already given us loglevel tags in
472 * the buffer. This code is here in case the
473 * log buffer has wrapped right round and scribbled
476 msg_level = default_message_loglevel;
478 _call_console_drivers(start_print, cur_index, msg_level);
480 start_print = cur_index;
485 _call_console_drivers(start_print, end, msg_level);
488 static void emit_log_char(char c)
490 LOG_BUF(log_end) = c;
492 if (log_end - log_start > log_buf_len)
493 log_start = log_end - log_buf_len;
494 if (log_end - con_start > log_buf_len)
495 con_start = log_end - log_buf_len;
496 if (logged_chars < log_buf_len)
501 * Zap console related locks when oopsing. Only zap at most once
502 * every 10 seconds, to leave time for slow consoles to print a
505 static void zap_locks(void)
507 static unsigned long oops_timestamp;
509 if (time_after_eq(jiffies, oops_timestamp) &&
510 !time_after(jiffies, oops_timestamp + 30 * HZ))
513 oops_timestamp = jiffies;
515 /* If a crash is occurring, make sure we can't deadlock */
516 spin_lock_init(&logbuf_lock);
517 /* And make sure that we print immediately */
518 init_MUTEX(&console_sem);
521 #if defined(CONFIG_PRINTK_TIME)
522 static int printk_time = 1;
524 static int printk_time = 0;
526 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
528 /* Check if we have any console registered that can be called early in boot. */
529 static int have_callable_console(void)
533 for (con = console_drivers; con; con = con->next)
534 if (con->flags & CON_ANYTIME)
541 * printk - print a kernel message
542 * @fmt: format string
544 * This is printk(). It can be called from any context. We want it to work.
546 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
547 * call the console drivers. If we fail to get the semaphore we place the output
548 * into the log buffer and return. The current holder of the console_sem will
549 * notice the new output in release_console_sem() and will send it to the
550 * consoles before releasing the semaphore.
552 * One effect of this deferred printing is that code which calls printk() and
553 * then changes console_loglevel may break. This is because console_loglevel
554 * is inspected when the actual printing occurs.
559 * See the vsnprintf() documentation for format string extensions over C99.
562 asmlinkage int printk(const char *fmt, ...)
568 r = vprintk(fmt, args);
574 /* cpu currently holding logbuf_lock */
575 static volatile unsigned int printk_cpu = UINT_MAX;
578 * Can we actually use the console at this time on this cpu?
580 * Console drivers may assume that per-cpu resources have
581 * been allocated. So unless they're explicitly marked as
582 * being able to cope (CON_ANYTIME) don't call them until
583 * this CPU is officially up.
585 static inline int can_use_console(unsigned int cpu)
587 return cpu_online(cpu) || have_callable_console();
591 * Try to get console ownership to actually show the kernel
592 * messages from a 'printk'. Return true (and with the
593 * console_semaphore held, and 'console_locked' set) if it
594 * is successful, false otherwise.
596 * This gets called with the 'logbuf_lock' spinlock held and
597 * interrupts disabled. It should return with 'lockbuf_lock'
598 * released but interrupts still disabled.
600 static int acquire_console_semaphore_for_printk(unsigned int cpu)
604 if (!try_acquire_console_sem()) {
608 * If we can't use the console, we need to release
609 * the console semaphore by hand to avoid flushing
610 * the buffer. We need to hold the console semaphore
611 * in order to do this test safely.
613 if (!can_use_console(cpu)) {
619 printk_cpu = UINT_MAX;
620 spin_unlock(&logbuf_lock);
623 static const char recursion_bug_msg [] =
624 KERN_CRIT "BUG: recent printk recursion!\n";
625 static int recursion_bug;
626 static int new_text_line = 1;
627 static char printk_buf[1024];
629 asmlinkage int vprintk(const char *fmt, va_list args)
632 int current_log_level = default_message_loglevel;
640 /* This stops the holder of console_sem just where we want him */
641 raw_local_irq_save(flags);
642 this_cpu = smp_processor_id();
645 * Ouch, printk recursed into itself!
647 if (unlikely(printk_cpu == this_cpu)) {
649 * If a crash is occurring during printk() on this CPU,
650 * then try to get the crash message out but make sure
651 * we can't deadlock. Otherwise just return to avoid the
652 * recursion and return - but flag the recursion so that
653 * it can be printed at the next appropriate moment:
655 if (!oops_in_progress) {
657 goto out_restore_irqs;
663 spin_lock(&logbuf_lock);
664 printk_cpu = this_cpu;
668 strcpy(printk_buf, recursion_bug_msg);
669 printed_len = sizeof(recursion_bug_msg);
671 /* Emit the output into the temporary buffer */
672 printed_len += vscnprintf(printk_buf + printed_len,
673 sizeof(printk_buf) - printed_len, fmt, args);
675 #ifdef CONFIG_DEBUG_LL
676 printascii(printk_buf);
680 * Copy the output into log_buf. If the caller didn't provide
681 * appropriate log level tags, we insert them here
683 for (p = printk_buf; *p; p++) {
685 /* If a token, set current_log_level and skip over */
686 if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
688 current_log_level = p[1] - '0';
693 /* Always output the token */
695 emit_log_char(current_log_level + '0');
701 /* Follow the token with the time */
704 unsigned long long t;
705 unsigned long nanosec_rem;
707 t = cpu_clock(printk_cpu);
708 nanosec_rem = do_div(t, 1000000000);
709 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
713 for (tp = tbuf; tp < tbuf + tlen; tp++)
728 * Try to acquire and then immediately release the
729 * console semaphore. The release will do all the
730 * actual magic (print out buffers, wake up klogd,
733 * The acquire_console_semaphore_for_printk() function
734 * will release 'logbuf_lock' regardless of whether it
735 * actually gets the semaphore or not.
737 if (acquire_console_semaphore_for_printk(this_cpu))
738 release_console_sem();
742 raw_local_irq_restore(flags);
747 EXPORT_SYMBOL(printk);
748 EXPORT_SYMBOL(vprintk);
752 asmlinkage long sys_syslog(int type, char __user *buf, int len)
757 static void call_console_drivers(unsigned start, unsigned end)
763 static int __add_preferred_console(char *name, int idx, char *options,
766 struct console_cmdline *c;
770 * See if this tty is not yet registered, and
771 * if we have a slot free.
773 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
774 if (strcmp(console_cmdline[i].name, name) == 0 &&
775 console_cmdline[i].index == idx) {
777 selected_console = i;
780 if (i == MAX_CMDLINECONSOLES)
783 selected_console = i;
784 c = &console_cmdline[i];
785 strlcpy(c->name, name, sizeof(c->name));
786 c->options = options;
787 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
788 c->brl_options = brl_options;
794 * Set up a list of consoles. Called from init/main.c
796 static int __init console_setup(char *str)
798 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
799 char *s, *options, *brl_options = NULL;
802 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
803 if (!memcmp(str, "brl,", 4)) {
806 } else if (!memcmp(str, "brl=", 4)) {
807 brl_options = str + 4;
808 str = strchr(brl_options, ',');
810 printk(KERN_ERR "need port name after brl=\n");
818 * Decode str into name, index, options.
820 if (str[0] >= '0' && str[0] <= '9') {
822 strncpy(buf + 4, str, sizeof(buf) - 5);
824 strncpy(buf, str, sizeof(buf) - 1);
826 buf[sizeof(buf) - 1] = 0;
827 if ((options = strchr(str, ',')) != NULL)
830 if (!strcmp(str, "ttya"))
831 strcpy(buf, "ttyS0");
832 if (!strcmp(str, "ttyb"))
833 strcpy(buf, "ttyS1");
835 for (s = buf; *s; s++)
836 if ((*s >= '0' && *s <= '9') || *s == ',')
838 idx = simple_strtoul(s, NULL, 10);
841 __add_preferred_console(buf, idx, options, brl_options);
842 console_set_on_cmdline = 1;
845 __setup("console=", console_setup);
848 * add_preferred_console - add a device to the list of preferred consoles.
851 * @options: options for this console
853 * The last preferred console added will be used for kernel messages
854 * and stdin/out/err for init. Normally this is used by console_setup
855 * above to handle user-supplied console arguments; however it can also
856 * be used by arch-specific code either to override the user or more
857 * commonly to provide a default console (ie from PROM variables) when
858 * the user has not supplied one.
860 int add_preferred_console(char *name, int idx, char *options)
862 return __add_preferred_console(name, idx, options, NULL);
865 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
867 struct console_cmdline *c;
870 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
871 if (strcmp(console_cmdline[i].name, name) == 0 &&
872 console_cmdline[i].index == idx) {
873 c = &console_cmdline[i];
874 strlcpy(c->name, name_new, sizeof(c->name));
875 c->name[sizeof(c->name) - 1] = 0;
876 c->options = options;
884 int console_suspend_enabled = 1;
885 EXPORT_SYMBOL(console_suspend_enabled);
887 static int __init console_suspend_disable(char *str)
889 console_suspend_enabled = 0;
892 __setup("no_console_suspend", console_suspend_disable);
895 * suspend_console - suspend the console subsystem
897 * This disables printk() while we go into suspend states
899 void suspend_console(void)
901 if (!console_suspend_enabled)
903 printk("Suspending console(s) (use no_console_suspend to debug)\n");
904 acquire_console_sem();
905 console_suspended = 1;
908 void resume_console(void)
910 if (!console_suspend_enabled)
912 console_suspended = 0;
913 release_console_sem();
917 * acquire_console_sem - lock the console system for exclusive use.
919 * Acquires a semaphore which guarantees that the caller has
920 * exclusive access to the console system and the console_drivers list.
922 * Can sleep, returns nothing.
924 void acquire_console_sem(void)
926 BUG_ON(in_interrupt());
927 if (console_suspended) {
928 down(&secondary_console_sem);
933 console_may_schedule = 1;
935 EXPORT_SYMBOL(acquire_console_sem);
937 int try_acquire_console_sem(void)
939 if (down_trylock(&console_sem))
942 console_may_schedule = 0;
945 EXPORT_SYMBOL(try_acquire_console_sem);
947 int is_console_locked(void)
949 return console_locked;
952 static DEFINE_PER_CPU(int, printk_pending);
954 void printk_tick(void)
956 if (__get_cpu_var(printk_pending)) {
957 __get_cpu_var(printk_pending) = 0;
958 wake_up_interruptible(&log_wait);
962 int printk_needs_cpu(int cpu)
964 return per_cpu(printk_pending, cpu);
967 void wake_up_klogd(void)
969 if (waitqueue_active(&log_wait))
970 __raw_get_cpu_var(printk_pending) = 1;
974 * release_console_sem - unlock the console system
976 * Releases the semaphore which the caller holds on the console system
977 * and the console driver list.
979 * While the semaphore was held, console output may have been buffered
980 * by printk(). If this is the case, release_console_sem() emits
981 * the output prior to releasing the semaphore.
983 * If there is output waiting for klogd, we wake it up.
985 * release_console_sem() may be called from any context.
987 void release_console_sem(void)
990 unsigned _con_start, _log_end;
991 unsigned wake_klogd = 0;
993 if (console_suspended) {
994 up(&secondary_console_sem);
998 console_may_schedule = 0;
1001 spin_lock_irqsave(&logbuf_lock, flags);
1002 wake_klogd |= log_start - log_end;
1003 if (con_start == log_end)
1004 break; /* Nothing to print */
1005 _con_start = con_start;
1007 con_start = log_end; /* Flush */
1008 spin_unlock(&logbuf_lock);
1009 stop_critical_timings(); /* don't trace print latency */
1010 call_console_drivers(_con_start, _log_end);
1011 start_critical_timings();
1012 local_irq_restore(flags);
1016 spin_unlock_irqrestore(&logbuf_lock, flags);
1020 EXPORT_SYMBOL(release_console_sem);
1023 * console_conditional_schedule - yield the CPU if required
1025 * If the console code is currently allowed to sleep, and
1026 * if this CPU should yield the CPU to another task, do
1029 * Must be called within acquire_console_sem().
1031 void __sched console_conditional_schedule(void)
1033 if (console_may_schedule)
1036 EXPORT_SYMBOL(console_conditional_schedule);
1038 void console_print(const char *s)
1040 printk(KERN_EMERG "%s", s);
1042 EXPORT_SYMBOL(console_print);
1044 void console_unblank(void)
1049 * console_unblank can no longer be called in interrupt context unless
1050 * oops_in_progress is set to 1..
1052 if (oops_in_progress) {
1053 if (down_trylock(&console_sem) != 0)
1056 acquire_console_sem();
1059 console_may_schedule = 0;
1060 for (c = console_drivers; c != NULL; c = c->next)
1061 if ((c->flags & CON_ENABLED) && c->unblank)
1063 release_console_sem();
1067 * Return the console tty driver structure and its associated index
1069 struct tty_driver *console_device(int *index)
1072 struct tty_driver *driver = NULL;
1074 acquire_console_sem();
1075 for (c = console_drivers; c != NULL; c = c->next) {
1078 driver = c->device(c, index);
1082 release_console_sem();
1087 * Prevent further output on the passed console device so that (for example)
1088 * serial drivers can disable console output before suspending a port, and can
1089 * re-enable output afterwards.
1091 void console_stop(struct console *console)
1093 acquire_console_sem();
1094 console->flags &= ~CON_ENABLED;
1095 release_console_sem();
1097 EXPORT_SYMBOL(console_stop);
1099 void console_start(struct console *console)
1101 acquire_console_sem();
1102 console->flags |= CON_ENABLED;
1103 release_console_sem();
1105 EXPORT_SYMBOL(console_start);
1108 * The console driver calls this routine during kernel initialization
1109 * to register the console printing procedure with printk() and to
1110 * print any messages that were printed by the kernel before the
1111 * console driver was initialized.
1113 void register_console(struct console *console)
1116 unsigned long flags;
1117 struct console *bootconsole = NULL;
1119 if (console_drivers) {
1120 if (console->flags & CON_BOOT)
1122 if (console_drivers->flags & CON_BOOT)
1123 bootconsole = console_drivers;
1126 if (preferred_console < 0 || bootconsole || !console_drivers)
1127 preferred_console = selected_console;
1129 if (console->early_setup)
1130 console->early_setup();
1133 * See if we want to use this console driver. If we
1134 * didn't select a console we take the first one
1135 * that registers here.
1137 if (preferred_console < 0) {
1138 if (console->index < 0)
1140 if (console->setup == NULL ||
1141 console->setup(console, NULL) == 0) {
1142 console->flags |= CON_ENABLED;
1143 if (console->device) {
1144 console->flags |= CON_CONSDEV;
1145 preferred_console = 0;
1151 * See if this console matches one we selected on
1154 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1156 if (strcmp(console_cmdline[i].name, console->name) != 0)
1158 if (console->index >= 0 &&
1159 console->index != console_cmdline[i].index)
1161 if (console->index < 0)
1162 console->index = console_cmdline[i].index;
1163 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1164 if (console_cmdline[i].brl_options) {
1165 console->flags |= CON_BRL;
1166 braille_register_console(console,
1167 console_cmdline[i].index,
1168 console_cmdline[i].options,
1169 console_cmdline[i].brl_options);
1173 if (console->setup &&
1174 console->setup(console, console_cmdline[i].options) != 0)
1176 console->flags |= CON_ENABLED;
1177 console->index = console_cmdline[i].index;
1178 if (i == selected_console) {
1179 console->flags |= CON_CONSDEV;
1180 preferred_console = selected_console;
1185 if (!(console->flags & CON_ENABLED))
1188 if (bootconsole && (console->flags & CON_CONSDEV)) {
1189 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1190 bootconsole->name, bootconsole->index,
1191 console->name, console->index);
1192 unregister_console(bootconsole);
1193 console->flags &= ~CON_PRINTBUFFER;
1195 printk(KERN_INFO "console [%s%d] enabled\n",
1196 console->name, console->index);
1200 * Put this console in the list - keep the
1201 * preferred driver at the head of the list.
1203 acquire_console_sem();
1204 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1205 console->next = console_drivers;
1206 console_drivers = console;
1208 console->next->flags &= ~CON_CONSDEV;
1210 console->next = console_drivers->next;
1211 console_drivers->next = console;
1213 if (console->flags & CON_PRINTBUFFER) {
1215 * release_console_sem() will print out the buffered messages
1218 spin_lock_irqsave(&logbuf_lock, flags);
1219 con_start = log_start;
1220 spin_unlock_irqrestore(&logbuf_lock, flags);
1222 release_console_sem();
1224 EXPORT_SYMBOL(register_console);
1226 int unregister_console(struct console *console)
1228 struct console *a, *b;
1231 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1232 if (console->flags & CON_BRL)
1233 return braille_unregister_console(console);
1236 acquire_console_sem();
1237 if (console_drivers == console) {
1238 console_drivers=console->next;
1240 } else if (console_drivers) {
1241 for (a=console_drivers->next, b=console_drivers ;
1242 a; b=a, a=b->next) {
1252 * If this isn't the last console and it has CON_CONSDEV set, we
1253 * need to set it on the next preferred console.
1255 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1256 console_drivers->flags |= CON_CONSDEV;
1258 release_console_sem();
1261 EXPORT_SYMBOL(unregister_console);
1263 static int __init disable_boot_consoles(void)
1265 if (console_drivers != NULL) {
1266 if (console_drivers->flags & CON_BOOT) {
1267 printk(KERN_INFO "turn off boot console %s%d\n",
1268 console_drivers->name, console_drivers->index);
1269 return unregister_console(console_drivers);
1274 late_initcall(disable_boot_consoles);
1276 #if defined CONFIG_PRINTK
1279 * printk rate limiting, lifted from the networking subsystem.
1281 * This enforces a rate limit: not more than 10 kernel messages
1282 * every 5s to make a denial-of-service attack impossible.
1284 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1286 int printk_ratelimit(void)
1288 return __ratelimit(&printk_ratelimit_state);
1290 EXPORT_SYMBOL(printk_ratelimit);
1293 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1294 * @caller_jiffies: pointer to caller's state
1295 * @interval_msecs: minimum interval between prints
1297 * printk_timed_ratelimit() returns true if more than @interval_msecs
1298 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1301 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1302 unsigned int interval_msecs)
1304 if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1305 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1310 EXPORT_SYMBOL(printk_timed_ratelimit);