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 * Return the number of unread characters in the log buffer.
242 static int log_buf_get_len(void)
248 * Copy a range of characters from the log buffer.
250 int log_buf_copy(char *dest, int idx, int len)
253 bool took_lock = false;
255 if (!oops_in_progress) {
256 spin_lock_irq(&logbuf_lock);
260 max = log_buf_get_len();
261 if (idx < 0 || idx >= max) {
267 idx += (log_end - max);
269 dest[len] = LOG_BUF(idx + len);
273 spin_unlock_irq(&logbuf_lock);
279 * Commands to do_syslog:
281 * 0 -- Close the log. Currently a NOP.
282 * 1 -- Open the log. Currently a NOP.
283 * 2 -- Read from the log.
284 * 3 -- Read all messages remaining in the ring buffer.
285 * 4 -- Read and clear all messages remaining in the ring buffer
286 * 5 -- Clear ring buffer.
287 * 6 -- Disable printk's to console
288 * 7 -- Enable printk's to console
289 * 8 -- Set level of messages printed to console
290 * 9 -- Return number of unread characters in the log buffer
291 * 10 -- Return size of the log buffer
293 int do_syslog(int type, char __user *buf, int len)
295 unsigned i, j, limit, count;
300 error = security_syslog(type);
305 case 0: /* Close log */
307 case 1: /* Open log */
309 case 2: /* Read from log */
316 if (!access_ok(VERIFY_WRITE, buf, len)) {
320 error = wait_event_interruptible(log_wait,
321 (log_start - log_end));
325 spin_lock_irq(&logbuf_lock);
326 while (!error && (log_start != log_end) && i < len) {
327 c = LOG_BUF(log_start);
329 spin_unlock_irq(&logbuf_lock);
330 error = __put_user(c,buf);
334 spin_lock_irq(&logbuf_lock);
336 spin_unlock_irq(&logbuf_lock);
340 case 4: /* Read/clear last kernel messages */
343 case 3: /* Read last kernel messages */
350 if (!access_ok(VERIFY_WRITE, buf, len)) {
355 if (count > log_buf_len)
357 spin_lock_irq(&logbuf_lock);
358 if (count > logged_chars)
359 count = logged_chars;
364 * __put_user() could sleep, and while we sleep
365 * printk() could overwrite the messages
366 * we try to copy to user space. Therefore
367 * the messages are copied in reverse. <manfreds>
369 for (i = 0; i < count && !error; i++) {
371 if (j + log_buf_len < log_end)
374 spin_unlock_irq(&logbuf_lock);
375 error = __put_user(c,&buf[count-1-i]);
377 spin_lock_irq(&logbuf_lock);
379 spin_unlock_irq(&logbuf_lock);
384 int offset = count-error;
385 /* buffer overflow during copy, correct user buffer. */
386 for (i = 0; i < error; i++) {
387 if (__get_user(c,&buf[i+offset]) ||
388 __put_user(c,&buf[i])) {
396 case 5: /* Clear ring buffer */
399 case 6: /* Disable logging to console */
400 console_loglevel = minimum_console_loglevel;
402 case 7: /* Enable logging to console */
403 console_loglevel = default_console_loglevel;
405 case 8: /* Set level of messages printed to console */
407 if (len < 1 || len > 8)
409 if (len < minimum_console_loglevel)
410 len = minimum_console_loglevel;
411 console_loglevel = len;
414 case 9: /* Number of chars in the log buffer */
415 error = log_end - log_start;
417 case 10: /* Size of the log buffer */
428 asmlinkage long sys_syslog(int type, char __user *buf, int len)
430 return do_syslog(type, buf, len);
434 * Call the console drivers on a range of log_buf
436 static void __call_console_drivers(unsigned start, unsigned end)
440 for (con = console_drivers; con; con = con->next) {
441 if ((con->flags & CON_ENABLED) && con->write &&
442 (cpu_online(smp_processor_id()) ||
443 (con->flags & CON_ANYTIME)))
444 con->write(con, &LOG_BUF(start), end - start);
448 static int __read_mostly ignore_loglevel;
450 static int __init ignore_loglevel_setup(char *str)
453 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
458 early_param("ignore_loglevel", ignore_loglevel_setup);
461 * Write out chars from start to end - 1 inclusive
463 static void _call_console_drivers(unsigned start,
464 unsigned end, int msg_log_level)
466 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
467 console_drivers && start != end) {
468 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
470 __call_console_drivers(start & LOG_BUF_MASK,
472 __call_console_drivers(0, end & LOG_BUF_MASK);
474 __call_console_drivers(start, end);
480 * Call the console drivers, asking them to write out
481 * log_buf[start] to log_buf[end - 1].
482 * The console_sem must be held.
484 static void call_console_drivers(unsigned start, unsigned end)
486 unsigned cur_index, start_print;
487 static int msg_level = -1;
489 BUG_ON(((int)(start - end)) > 0);
493 while (cur_index != end) {
494 if (msg_level < 0 && ((end - cur_index) > 2) &&
495 LOG_BUF(cur_index + 0) == '<' &&
496 LOG_BUF(cur_index + 1) >= '0' &&
497 LOG_BUF(cur_index + 1) <= '7' &&
498 LOG_BUF(cur_index + 2) == '>') {
499 msg_level = LOG_BUF(cur_index + 1) - '0';
501 start_print = cur_index;
503 while (cur_index != end) {
504 char c = LOG_BUF(cur_index);
510 * printk() has already given us loglevel tags in
511 * the buffer. This code is here in case the
512 * log buffer has wrapped right round and scribbled
515 msg_level = default_message_loglevel;
517 _call_console_drivers(start_print, cur_index, msg_level);
519 start_print = cur_index;
524 _call_console_drivers(start_print, end, msg_level);
527 static void emit_log_char(char c)
529 LOG_BUF(log_end) = c;
531 if (log_end - log_start > log_buf_len)
532 log_start = log_end - log_buf_len;
533 if (log_end - con_start > log_buf_len)
534 con_start = log_end - log_buf_len;
535 if (logged_chars < log_buf_len)
540 * Zap console related locks when oopsing. Only zap at most once
541 * every 10 seconds, to leave time for slow consoles to print a
544 static void zap_locks(void)
546 static unsigned long oops_timestamp;
548 if (time_after_eq(jiffies, oops_timestamp) &&
549 !time_after(jiffies, oops_timestamp + 30 * HZ))
552 oops_timestamp = jiffies;
554 /* If a crash is occurring, make sure we can't deadlock */
555 spin_lock_init(&logbuf_lock);
556 /* And make sure that we print immediately */
557 init_MUTEX(&console_sem);
560 #if defined(CONFIG_PRINTK_TIME)
561 static int printk_time = 1;
563 static int printk_time = 0;
565 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
567 /* Check if we have any console registered that can be called early in boot. */
568 static int have_callable_console(void)
572 for (con = console_drivers; con; con = con->next)
573 if (con->flags & CON_ANYTIME)
580 * printk - print a kernel message
581 * @fmt: format string
583 * This is printk(). It can be called from any context. We want it to work.
585 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
586 * call the console drivers. If we fail to get the semaphore we place the output
587 * into the log buffer and return. The current holder of the console_sem will
588 * notice the new output in release_console_sem() and will send it to the
589 * consoles before releasing the semaphore.
591 * One effect of this deferred printing is that code which calls printk() and
592 * then changes console_loglevel may break. This is because console_loglevel
593 * is inspected when the actual printing occurs.
598 * See the vsnprintf() documentation for format string extensions over C99.
601 asmlinkage int printk(const char *fmt, ...)
607 r = vprintk(fmt, args);
613 /* cpu currently holding logbuf_lock */
614 static volatile unsigned int printk_cpu = UINT_MAX;
617 * Can we actually use the console at this time on this cpu?
619 * Console drivers may assume that per-cpu resources have
620 * been allocated. So unless they're explicitly marked as
621 * being able to cope (CON_ANYTIME) don't call them until
622 * this CPU is officially up.
624 static inline int can_use_console(unsigned int cpu)
626 return cpu_online(cpu) || have_callable_console();
630 * Try to get console ownership to actually show the kernel
631 * messages from a 'printk'. Return true (and with the
632 * console_semaphore held, and 'console_locked' set) if it
633 * is successful, false otherwise.
635 * This gets called with the 'logbuf_lock' spinlock held and
636 * interrupts disabled. It should return with 'lockbuf_lock'
637 * released but interrupts still disabled.
639 static int acquire_console_semaphore_for_printk(unsigned int cpu)
643 if (!try_acquire_console_sem()) {
647 * If we can't use the console, we need to release
648 * the console semaphore by hand to avoid flushing
649 * the buffer. We need to hold the console semaphore
650 * in order to do this test safely.
652 if (!can_use_console(cpu)) {
658 printk_cpu = UINT_MAX;
659 spin_unlock(&logbuf_lock);
662 static const char recursion_bug_msg [] =
663 KERN_CRIT "BUG: recent printk recursion!\n";
664 static int recursion_bug;
665 static int new_text_line = 1;
666 static char printk_buf[1024];
668 asmlinkage int vprintk(const char *fmt, va_list args)
671 int current_log_level = default_message_loglevel;
679 /* This stops the holder of console_sem just where we want him */
680 raw_local_irq_save(flags);
681 this_cpu = smp_processor_id();
684 * Ouch, printk recursed into itself!
686 if (unlikely(printk_cpu == this_cpu)) {
688 * If a crash is occurring during printk() on this CPU,
689 * then try to get the crash message out but make sure
690 * we can't deadlock. Otherwise just return to avoid the
691 * recursion and return - but flag the recursion so that
692 * it can be printed at the next appropriate moment:
694 if (!oops_in_progress) {
696 goto out_restore_irqs;
702 spin_lock(&logbuf_lock);
703 printk_cpu = this_cpu;
707 strcpy(printk_buf, recursion_bug_msg);
708 printed_len = sizeof(recursion_bug_msg);
710 /* Emit the output into the temporary buffer */
711 printed_len += vscnprintf(printk_buf + printed_len,
712 sizeof(printk_buf) - printed_len, fmt, args);
714 #ifdef CONFIG_DEBUG_LL
715 printascii(printk_buf);
719 * Copy the output into log_buf. If the caller didn't provide
720 * appropriate log level tags, we insert them here
722 for (p = printk_buf; *p; p++) {
724 /* If a token, set current_log_level and skip over */
725 if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
727 current_log_level = p[1] - '0';
732 /* Always output the token */
734 emit_log_char(current_log_level + '0');
740 /* Follow the token with the time */
743 unsigned long long t;
744 unsigned long nanosec_rem;
746 t = cpu_clock(printk_cpu);
747 nanosec_rem = do_div(t, 1000000000);
748 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
752 for (tp = tbuf; tp < tbuf + tlen; tp++)
767 * Try to acquire and then immediately release the
768 * console semaphore. The release will do all the
769 * actual magic (print out buffers, wake up klogd,
772 * The acquire_console_semaphore_for_printk() function
773 * will release 'logbuf_lock' regardless of whether it
774 * actually gets the semaphore or not.
776 if (acquire_console_semaphore_for_printk(this_cpu))
777 release_console_sem();
781 raw_local_irq_restore(flags);
786 EXPORT_SYMBOL(printk);
787 EXPORT_SYMBOL(vprintk);
791 asmlinkage long sys_syslog(int type, char __user *buf, int len)
796 static void call_console_drivers(unsigned start, unsigned end)
802 static int __add_preferred_console(char *name, int idx, char *options,
805 struct console_cmdline *c;
809 * See if this tty is not yet registered, and
810 * if we have a slot free.
812 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
813 if (strcmp(console_cmdline[i].name, name) == 0 &&
814 console_cmdline[i].index == idx) {
816 selected_console = i;
819 if (i == MAX_CMDLINECONSOLES)
822 selected_console = i;
823 c = &console_cmdline[i];
824 strlcpy(c->name, name, sizeof(c->name));
825 c->options = options;
826 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
827 c->brl_options = brl_options;
833 * Set up a list of consoles. Called from init/main.c
835 static int __init console_setup(char *str)
837 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
838 char *s, *options, *brl_options = NULL;
841 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
842 if (!memcmp(str, "brl,", 4)) {
845 } else if (!memcmp(str, "brl=", 4)) {
846 brl_options = str + 4;
847 str = strchr(brl_options, ',');
849 printk(KERN_ERR "need port name after brl=\n");
857 * Decode str into name, index, options.
859 if (str[0] >= '0' && str[0] <= '9') {
861 strncpy(buf + 4, str, sizeof(buf) - 5);
863 strncpy(buf, str, sizeof(buf) - 1);
865 buf[sizeof(buf) - 1] = 0;
866 if ((options = strchr(str, ',')) != NULL)
869 if (!strcmp(str, "ttya"))
870 strcpy(buf, "ttyS0");
871 if (!strcmp(str, "ttyb"))
872 strcpy(buf, "ttyS1");
874 for (s = buf; *s; s++)
875 if ((*s >= '0' && *s <= '9') || *s == ',')
877 idx = simple_strtoul(s, NULL, 10);
880 __add_preferred_console(buf, idx, options, brl_options);
881 console_set_on_cmdline = 1;
884 __setup("console=", console_setup);
887 * add_preferred_console - add a device to the list of preferred consoles.
890 * @options: options for this console
892 * The last preferred console added will be used for kernel messages
893 * and stdin/out/err for init. Normally this is used by console_setup
894 * above to handle user-supplied console arguments; however it can also
895 * be used by arch-specific code either to override the user or more
896 * commonly to provide a default console (ie from PROM variables) when
897 * the user has not supplied one.
899 int add_preferred_console(char *name, int idx, char *options)
901 return __add_preferred_console(name, idx, options, NULL);
904 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
906 struct console_cmdline *c;
909 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
910 if (strcmp(console_cmdline[i].name, name) == 0 &&
911 console_cmdline[i].index == idx) {
912 c = &console_cmdline[i];
913 strlcpy(c->name, name_new, sizeof(c->name));
914 c->name[sizeof(c->name) - 1] = 0;
915 c->options = options;
923 int console_suspend_enabled = 1;
924 EXPORT_SYMBOL(console_suspend_enabled);
926 static int __init console_suspend_disable(char *str)
928 console_suspend_enabled = 0;
931 __setup("no_console_suspend", console_suspend_disable);
934 * suspend_console - suspend the console subsystem
936 * This disables printk() while we go into suspend states
938 void suspend_console(void)
940 if (!console_suspend_enabled)
942 printk("Suspending console(s) (use no_console_suspend to debug)\n");
943 acquire_console_sem();
944 console_suspended = 1;
947 void resume_console(void)
949 if (!console_suspend_enabled)
951 console_suspended = 0;
952 release_console_sem();
956 * acquire_console_sem - lock the console system for exclusive use.
958 * Acquires a semaphore which guarantees that the caller has
959 * exclusive access to the console system and the console_drivers list.
961 * Can sleep, returns nothing.
963 void acquire_console_sem(void)
965 BUG_ON(in_interrupt());
966 if (console_suspended) {
967 down(&secondary_console_sem);
972 console_may_schedule = 1;
974 EXPORT_SYMBOL(acquire_console_sem);
976 int try_acquire_console_sem(void)
978 if (down_trylock(&console_sem))
981 console_may_schedule = 0;
984 EXPORT_SYMBOL(try_acquire_console_sem);
986 int is_console_locked(void)
988 return console_locked;
991 static DEFINE_PER_CPU(int, printk_pending);
993 void printk_tick(void)
995 if (__get_cpu_var(printk_pending)) {
996 __get_cpu_var(printk_pending) = 0;
997 wake_up_interruptible(&log_wait);
1001 int printk_needs_cpu(int cpu)
1003 return per_cpu(printk_pending, cpu);
1006 void wake_up_klogd(void)
1008 if (waitqueue_active(&log_wait))
1009 __raw_get_cpu_var(printk_pending) = 1;
1013 * release_console_sem - unlock the console system
1015 * Releases the semaphore which the caller holds on the console system
1016 * and the console driver list.
1018 * While the semaphore was held, console output may have been buffered
1019 * by printk(). If this is the case, release_console_sem() emits
1020 * the output prior to releasing the semaphore.
1022 * If there is output waiting for klogd, we wake it up.
1024 * release_console_sem() may be called from any context.
1026 void release_console_sem(void)
1028 unsigned long flags;
1029 unsigned _con_start, _log_end;
1030 unsigned wake_klogd = 0;
1032 if (console_suspended) {
1033 up(&secondary_console_sem);
1037 console_may_schedule = 0;
1040 spin_lock_irqsave(&logbuf_lock, flags);
1041 wake_klogd |= log_start - log_end;
1042 if (con_start == log_end)
1043 break; /* Nothing to print */
1044 _con_start = con_start;
1046 con_start = log_end; /* Flush */
1047 spin_unlock(&logbuf_lock);
1048 stop_critical_timings(); /* don't trace print latency */
1049 call_console_drivers(_con_start, _log_end);
1050 start_critical_timings();
1051 local_irq_restore(flags);
1055 spin_unlock_irqrestore(&logbuf_lock, flags);
1059 EXPORT_SYMBOL(release_console_sem);
1062 * console_conditional_schedule - yield the CPU if required
1064 * If the console code is currently allowed to sleep, and
1065 * if this CPU should yield the CPU to another task, do
1068 * Must be called within acquire_console_sem().
1070 void __sched console_conditional_schedule(void)
1072 if (console_may_schedule)
1075 EXPORT_SYMBOL(console_conditional_schedule);
1077 void console_print(const char *s)
1079 printk(KERN_EMERG "%s", s);
1081 EXPORT_SYMBOL(console_print);
1083 void console_unblank(void)
1088 * console_unblank can no longer be called in interrupt context unless
1089 * oops_in_progress is set to 1..
1091 if (oops_in_progress) {
1092 if (down_trylock(&console_sem) != 0)
1095 acquire_console_sem();
1098 console_may_schedule = 0;
1099 for (c = console_drivers; c != NULL; c = c->next)
1100 if ((c->flags & CON_ENABLED) && c->unblank)
1102 release_console_sem();
1106 * Return the console tty driver structure and its associated index
1108 struct tty_driver *console_device(int *index)
1111 struct tty_driver *driver = NULL;
1113 acquire_console_sem();
1114 for (c = console_drivers; c != NULL; c = c->next) {
1117 driver = c->device(c, index);
1121 release_console_sem();
1126 * Prevent further output on the passed console device so that (for example)
1127 * serial drivers can disable console output before suspending a port, and can
1128 * re-enable output afterwards.
1130 void console_stop(struct console *console)
1132 acquire_console_sem();
1133 console->flags &= ~CON_ENABLED;
1134 release_console_sem();
1136 EXPORT_SYMBOL(console_stop);
1138 void console_start(struct console *console)
1140 acquire_console_sem();
1141 console->flags |= CON_ENABLED;
1142 release_console_sem();
1144 EXPORT_SYMBOL(console_start);
1147 * The console driver calls this routine during kernel initialization
1148 * to register the console printing procedure with printk() and to
1149 * print any messages that were printed by the kernel before the
1150 * console driver was initialized.
1152 void register_console(struct console *console)
1155 unsigned long flags;
1156 struct console *bootconsole = NULL;
1158 if (console_drivers) {
1159 if (console->flags & CON_BOOT)
1161 if (console_drivers->flags & CON_BOOT)
1162 bootconsole = console_drivers;
1165 if (preferred_console < 0 || bootconsole || !console_drivers)
1166 preferred_console = selected_console;
1168 if (console->early_setup)
1169 console->early_setup();
1172 * See if we want to use this console driver. If we
1173 * didn't select a console we take the first one
1174 * that registers here.
1176 if (preferred_console < 0) {
1177 if (console->index < 0)
1179 if (console->setup == NULL ||
1180 console->setup(console, NULL) == 0) {
1181 console->flags |= CON_ENABLED;
1182 if (console->device) {
1183 console->flags |= CON_CONSDEV;
1184 preferred_console = 0;
1190 * See if this console matches one we selected on
1193 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1195 if (strcmp(console_cmdline[i].name, console->name) != 0)
1197 if (console->index >= 0 &&
1198 console->index != console_cmdline[i].index)
1200 if (console->index < 0)
1201 console->index = console_cmdline[i].index;
1202 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1203 if (console_cmdline[i].brl_options) {
1204 console->flags |= CON_BRL;
1205 braille_register_console(console,
1206 console_cmdline[i].index,
1207 console_cmdline[i].options,
1208 console_cmdline[i].brl_options);
1212 if (console->setup &&
1213 console->setup(console, console_cmdline[i].options) != 0)
1215 console->flags |= CON_ENABLED;
1216 console->index = console_cmdline[i].index;
1217 if (i == selected_console) {
1218 console->flags |= CON_CONSDEV;
1219 preferred_console = selected_console;
1224 if (!(console->flags & CON_ENABLED))
1227 if (bootconsole && (console->flags & CON_CONSDEV)) {
1228 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1229 bootconsole->name, bootconsole->index,
1230 console->name, console->index);
1231 unregister_console(bootconsole);
1232 console->flags &= ~CON_PRINTBUFFER;
1234 printk(KERN_INFO "console [%s%d] enabled\n",
1235 console->name, console->index);
1239 * Put this console in the list - keep the
1240 * preferred driver at the head of the list.
1242 acquire_console_sem();
1243 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1244 console->next = console_drivers;
1245 console_drivers = console;
1247 console->next->flags &= ~CON_CONSDEV;
1249 console->next = console_drivers->next;
1250 console_drivers->next = console;
1252 if (console->flags & CON_PRINTBUFFER) {
1254 * release_console_sem() will print out the buffered messages
1257 spin_lock_irqsave(&logbuf_lock, flags);
1258 con_start = log_start;
1259 spin_unlock_irqrestore(&logbuf_lock, flags);
1261 release_console_sem();
1263 EXPORT_SYMBOL(register_console);
1265 int unregister_console(struct console *console)
1267 struct console *a, *b;
1270 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1271 if (console->flags & CON_BRL)
1272 return braille_unregister_console(console);
1275 acquire_console_sem();
1276 if (console_drivers == console) {
1277 console_drivers=console->next;
1279 } else if (console_drivers) {
1280 for (a=console_drivers->next, b=console_drivers ;
1281 a; b=a, a=b->next) {
1291 * If this isn't the last console and it has CON_CONSDEV set, we
1292 * need to set it on the next preferred console.
1294 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1295 console_drivers->flags |= CON_CONSDEV;
1297 release_console_sem();
1300 EXPORT_SYMBOL(unregister_console);
1302 static int __init disable_boot_consoles(void)
1304 if (console_drivers != NULL) {
1305 if (console_drivers->flags & CON_BOOT) {
1306 printk(KERN_INFO "turn off boot console %s%d\n",
1307 console_drivers->name, console_drivers->index);
1308 return unregister_console(console_drivers);
1313 late_initcall(disable_boot_consoles);
1315 #if defined CONFIG_PRINTK
1318 * printk rate limiting, lifted from the networking subsystem.
1320 * This enforces a rate limit: not more than 10 kernel messages
1321 * every 5s to make a denial-of-service attack impossible.
1323 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1325 int printk_ratelimit(void)
1327 return __ratelimit(&printk_ratelimit_state);
1329 EXPORT_SYMBOL(printk_ratelimit);
1332 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1333 * @caller_jiffies: pointer to caller's state
1334 * @interval_msecs: minimum interval between prints
1336 * printk_timed_ratelimit() returns true if more than @interval_msecs
1337 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1340 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1341 unsigned int interval_msecs)
1343 if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1344 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1349 EXPORT_SYMBOL(printk_timed_ratelimit);