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>
35 #include <linux/kexec.h>
37 #include <asm/uaccess.h>
40 * Architectures can override it:
42 void asmlinkage
__attribute__((weak
)) early_printk(const char *fmt
, ...)
46 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
48 /* printk's without a loglevel use this.. */
49 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
51 /* We show everything that is MORE important than this.. */
52 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
53 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
55 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
57 int console_printk
[4] = {
58 DEFAULT_CONSOLE_LOGLEVEL
, /* console_loglevel */
59 DEFAULT_MESSAGE_LOGLEVEL
, /* default_message_loglevel */
60 MINIMUM_CONSOLE_LOGLEVEL
, /* minimum_console_loglevel */
61 DEFAULT_CONSOLE_LOGLEVEL
, /* default_console_loglevel */
65 * Low level drivers may need that to know if they can schedule in
66 * their unblank() callback or not. So let's export it.
69 EXPORT_SYMBOL(oops_in_progress
);
72 * console_sem protects the console_drivers list, and also
73 * provides serialisation for access to the entire console
76 static DECLARE_MUTEX(console_sem
);
77 struct console
*console_drivers
;
78 EXPORT_SYMBOL_GPL(console_drivers
);
81 * This is used for debugging the mess that is the VT code by
82 * keeping track if we have the console semaphore held. It's
83 * definitely not the perfect debug tool (we don't know if _WE_
84 * hold it are racing, but it helps tracking those weird code
85 * path in the console code where we end up in places I want
86 * locked without the console sempahore held
88 static int console_locked
, console_suspended
;
91 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
92 * It is also used in interesting ways to provide interlocking in
93 * release_console_sem().
95 static DEFINE_SPINLOCK(logbuf_lock
);
97 #define LOG_BUF_MASK (log_buf_len-1)
98 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
101 * The indices into log_buf are not constrained to log_buf_len - they
102 * must be masked before subscripting
104 static unsigned log_start
; /* Index into log_buf: next char to be read by syslog() */
105 static unsigned con_start
; /* Index into log_buf: next char to be sent to consoles */
106 static unsigned log_end
; /* Index into log_buf: most-recently-written-char + 1 */
109 * Array of consoles built from command line options (console=)
111 struct console_cmdline
113 char name
[8]; /* Name of the driver */
114 int index
; /* Minor dev. to use */
115 char *options
; /* Options for the driver */
116 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
117 char *brl_options
; /* Options for braille driver */
121 #define MAX_CMDLINECONSOLES 8
123 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
124 static int selected_console
= -1;
125 static int preferred_console
= -1;
126 int console_set_on_cmdline
;
127 EXPORT_SYMBOL(console_set_on_cmdline
);
129 /* Flag: console code may call schedule() */
130 static int console_may_schedule
;
134 static char __log_buf
[__LOG_BUF_LEN
];
135 static char *log_buf
= __log_buf
;
136 static int log_buf_len
= __LOG_BUF_LEN
;
137 static unsigned logged_chars
; /* Number of chars produced since last read+clear operation */
141 * This appends the listed symbols to /proc/vmcoreinfo
143 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
144 * obtain access to symbols that are otherwise very difficult to locate. These
145 * symbols are specifically used so that utilities can access and extract the
146 * dmesg log from a vmcore file after a crash.
148 void log_buf_kexec_setup(void)
150 VMCOREINFO_SYMBOL(log_buf
);
151 VMCOREINFO_SYMBOL(log_end
);
152 VMCOREINFO_SYMBOL(log_buf_len
);
153 VMCOREINFO_SYMBOL(logged_chars
);
157 static int __init
log_buf_len_setup(char *str
)
159 unsigned size
= memparse(str
, &str
);
163 size
= roundup_pow_of_two(size
);
164 if (size
> log_buf_len
) {
165 unsigned start
, dest_idx
, offset
;
168 new_log_buf
= alloc_bootmem(size
);
170 printk(KERN_WARNING
"log_buf_len: allocation failed\n");
174 spin_lock_irqsave(&logbuf_lock
, flags
);
176 log_buf
= new_log_buf
;
178 offset
= start
= min(con_start
, log_start
);
180 while (start
!= log_end
) {
181 log_buf
[dest_idx
] = __log_buf
[start
& (__LOG_BUF_LEN
- 1)];
188 spin_unlock_irqrestore(&logbuf_lock
, flags
);
190 printk(KERN_NOTICE
"log_buf_len: %d\n", log_buf_len
);
196 __setup("log_buf_len=", log_buf_len_setup
);
198 #ifdef CONFIG_BOOT_PRINTK_DELAY
200 static unsigned int boot_delay
; /* msecs delay after each printk during bootup */
201 static unsigned long long printk_delay_msec
; /* per msec, based on boot_delay */
203 static int __init
boot_delay_setup(char *str
)
206 unsigned long long loops_per_msec
;
208 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
209 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
211 get_option(&str
, &boot_delay
);
212 if (boot_delay
> 10 * 1000)
215 printk_delay_msec
= loops_per_msec
;
216 printk(KERN_DEBUG
"boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
217 "HZ: %d, printk_delay_msec: %llu\n",
218 boot_delay
, preset_lpj
, lpj
, HZ
, printk_delay_msec
);
221 __setup("boot_delay=", boot_delay_setup
);
223 static void boot_delay_msec(void)
225 unsigned long long k
;
226 unsigned long timeout
;
228 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
231 k
= (unsigned long long)printk_delay_msec
* boot_delay
;
233 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
238 * use (volatile) jiffies to prevent
239 * compiler reduction; loop termination via jiffies
240 * is secondary and may or may not happen.
242 if (time_after(jiffies
, timeout
))
244 touch_nmi_watchdog();
248 static inline void boot_delay_msec(void)
254 * Commands to do_syslog:
256 * 0 -- Close the log. Currently a NOP.
257 * 1 -- Open the log. Currently a NOP.
258 * 2 -- Read from the log.
259 * 3 -- Read all messages remaining in the ring buffer.
260 * 4 -- Read and clear all messages remaining in the ring buffer
261 * 5 -- Clear ring buffer.
262 * 6 -- Disable printk's to console
263 * 7 -- Enable printk's to console
264 * 8 -- Set level of messages printed to console
265 * 9 -- Return number of unread characters in the log buffer
266 * 10 -- Return size of the log buffer
268 int do_syslog(int type
, char __user
*buf
, int len
)
270 unsigned i
, j
, limit
, count
;
275 error
= security_syslog(type
);
280 case 0: /* Close log */
282 case 1: /* Open log */
284 case 2: /* Read from log */
291 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
295 error
= wait_event_interruptible(log_wait
,
296 (log_start
- log_end
));
300 spin_lock_irq(&logbuf_lock
);
301 while (!error
&& (log_start
!= log_end
) && i
< len
) {
302 c
= LOG_BUF(log_start
);
304 spin_unlock_irq(&logbuf_lock
);
305 error
= __put_user(c
,buf
);
309 spin_lock_irq(&logbuf_lock
);
311 spin_unlock_irq(&logbuf_lock
);
315 case 4: /* Read/clear last kernel messages */
318 case 3: /* Read last kernel messages */
325 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
330 if (count
> log_buf_len
)
332 spin_lock_irq(&logbuf_lock
);
333 if (count
> logged_chars
)
334 count
= logged_chars
;
339 * __put_user() could sleep, and while we sleep
340 * printk() could overwrite the messages
341 * we try to copy to user space. Therefore
342 * the messages are copied in reverse. <manfreds>
344 for (i
= 0; i
< count
&& !error
; i
++) {
346 if (j
+ log_buf_len
< log_end
)
349 spin_unlock_irq(&logbuf_lock
);
350 error
= __put_user(c
,&buf
[count
-1-i
]);
352 spin_lock_irq(&logbuf_lock
);
354 spin_unlock_irq(&logbuf_lock
);
359 int offset
= count
-error
;
360 /* buffer overflow during copy, correct user buffer. */
361 for (i
= 0; i
< error
; i
++) {
362 if (__get_user(c
,&buf
[i
+offset
]) ||
363 __put_user(c
,&buf
[i
])) {
371 case 5: /* Clear ring buffer */
374 case 6: /* Disable logging to console */
375 console_loglevel
= minimum_console_loglevel
;
377 case 7: /* Enable logging to console */
378 console_loglevel
= default_console_loglevel
;
380 case 8: /* Set level of messages printed to console */
382 if (len
< 1 || len
> 8)
384 if (len
< minimum_console_loglevel
)
385 len
= minimum_console_loglevel
;
386 console_loglevel
= len
;
389 case 9: /* Number of chars in the log buffer */
390 error
= log_end
- log_start
;
392 case 10: /* Size of the log buffer */
403 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
405 return do_syslog(type
, buf
, len
);
409 * Call the console drivers on a range of log_buf
411 static void __call_console_drivers(unsigned start
, unsigned end
)
415 for (con
= console_drivers
; con
; con
= con
->next
) {
416 if ((con
->flags
& CON_ENABLED
) && con
->write
&&
417 (cpu_online(smp_processor_id()) ||
418 (con
->flags
& CON_ANYTIME
)))
419 con
->write(con
, &LOG_BUF(start
), end
- start
);
423 static int __read_mostly ignore_loglevel
;
425 static int __init
ignore_loglevel_setup(char *str
)
428 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
433 early_param("ignore_loglevel", ignore_loglevel_setup
);
436 * Write out chars from start to end - 1 inclusive
438 static void _call_console_drivers(unsigned start
,
439 unsigned end
, int msg_log_level
)
441 if ((msg_log_level
< console_loglevel
|| ignore_loglevel
) &&
442 console_drivers
&& start
!= end
) {
443 if ((start
& LOG_BUF_MASK
) > (end
& LOG_BUF_MASK
)) {
445 __call_console_drivers(start
& LOG_BUF_MASK
,
447 __call_console_drivers(0, end
& LOG_BUF_MASK
);
449 __call_console_drivers(start
, end
);
455 * Call the console drivers, asking them to write out
456 * log_buf[start] to log_buf[end - 1].
457 * The console_sem must be held.
459 static void call_console_drivers(unsigned start
, unsigned end
)
461 unsigned cur_index
, start_print
;
462 static int msg_level
= -1;
464 BUG_ON(((int)(start
- end
)) > 0);
468 while (cur_index
!= end
) {
469 if (msg_level
< 0 && ((end
- cur_index
) > 2) &&
470 LOG_BUF(cur_index
+ 0) == '<' &&
471 LOG_BUF(cur_index
+ 1) >= '0' &&
472 LOG_BUF(cur_index
+ 1) <= '7' &&
473 LOG_BUF(cur_index
+ 2) == '>') {
474 msg_level
= LOG_BUF(cur_index
+ 1) - '0';
476 start_print
= cur_index
;
478 while (cur_index
!= end
) {
479 char c
= LOG_BUF(cur_index
);
485 * printk() has already given us loglevel tags in
486 * the buffer. This code is here in case the
487 * log buffer has wrapped right round and scribbled
490 msg_level
= default_message_loglevel
;
492 _call_console_drivers(start_print
, cur_index
, msg_level
);
494 start_print
= cur_index
;
499 _call_console_drivers(start_print
, end
, msg_level
);
502 static void emit_log_char(char c
)
504 LOG_BUF(log_end
) = c
;
506 if (log_end
- log_start
> log_buf_len
)
507 log_start
= log_end
- log_buf_len
;
508 if (log_end
- con_start
> log_buf_len
)
509 con_start
= log_end
- log_buf_len
;
510 if (logged_chars
< log_buf_len
)
515 * Zap console related locks when oopsing. Only zap at most once
516 * every 10 seconds, to leave time for slow consoles to print a
519 static void zap_locks(void)
521 static unsigned long oops_timestamp
;
523 if (time_after_eq(jiffies
, oops_timestamp
) &&
524 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
527 oops_timestamp
= jiffies
;
529 /* If a crash is occurring, make sure we can't deadlock */
530 spin_lock_init(&logbuf_lock
);
531 /* And make sure that we print immediately */
532 init_MUTEX(&console_sem
);
535 #if defined(CONFIG_PRINTK_TIME)
536 static int printk_time
= 1;
538 static int printk_time
= 0;
540 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
542 /* Check if we have any console registered that can be called early in boot. */
543 static int have_callable_console(void)
547 for (con
= console_drivers
; con
; con
= con
->next
)
548 if (con
->flags
& CON_ANYTIME
)
555 * printk - print a kernel message
556 * @fmt: format string
558 * This is printk(). It can be called from any context. We want it to work.
560 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
561 * call the console drivers. If we fail to get the semaphore we place the output
562 * into the log buffer and return. The current holder of the console_sem will
563 * notice the new output in release_console_sem() and will send it to the
564 * consoles before releasing the semaphore.
566 * One effect of this deferred printing is that code which calls printk() and
567 * then changes console_loglevel may break. This is because console_loglevel
568 * is inspected when the actual printing occurs.
573 * See the vsnprintf() documentation for format string extensions over C99.
576 asmlinkage
int printk(const char *fmt
, ...)
582 r
= vprintk(fmt
, args
);
588 /* cpu currently holding logbuf_lock */
589 static volatile unsigned int printk_cpu
= UINT_MAX
;
592 * Can we actually use the console at this time on this cpu?
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 static inline int can_use_console(unsigned int cpu
)
601 return cpu_online(cpu
) || have_callable_console();
605 * Try to get console ownership to actually show the kernel
606 * messages from a 'printk'. Return true (and with the
607 * console_semaphore held, and 'console_locked' set) if it
608 * is successful, false otherwise.
610 * This gets called with the 'logbuf_lock' spinlock held and
611 * interrupts disabled. It should return with 'lockbuf_lock'
612 * released but interrupts still disabled.
614 static int acquire_console_semaphore_for_printk(unsigned int cpu
)
618 if (!try_acquire_console_sem()) {
622 * If we can't use the console, we need to release
623 * the console semaphore by hand to avoid flushing
624 * the buffer. We need to hold the console semaphore
625 * in order to do this test safely.
627 if (!can_use_console(cpu
)) {
633 printk_cpu
= UINT_MAX
;
634 spin_unlock(&logbuf_lock
);
637 static const char recursion_bug_msg
[] =
638 KERN_CRIT
"BUG: recent printk recursion!\n";
639 static int recursion_bug
;
640 static int new_text_line
= 1;
641 static char printk_buf
[1024];
643 asmlinkage
int vprintk(const char *fmt
, va_list args
)
646 int current_log_level
= default_message_loglevel
;
654 /* This stops the holder of console_sem just where we want him */
655 raw_local_irq_save(flags
);
656 this_cpu
= smp_processor_id();
659 * Ouch, printk recursed into itself!
661 if (unlikely(printk_cpu
== this_cpu
)) {
663 * If a crash is occurring during printk() on this CPU,
664 * then try to get the crash message out but make sure
665 * we can't deadlock. Otherwise just return to avoid the
666 * recursion and return - but flag the recursion so that
667 * it can be printed at the next appropriate moment:
669 if (!oops_in_progress
) {
671 goto out_restore_irqs
;
677 spin_lock(&logbuf_lock
);
678 printk_cpu
= this_cpu
;
682 strcpy(printk_buf
, recursion_bug_msg
);
683 printed_len
= strlen(recursion_bug_msg
);
685 /* Emit the output into the temporary buffer */
686 printed_len
+= vscnprintf(printk_buf
+ printed_len
,
687 sizeof(printk_buf
) - printed_len
, fmt
, args
);
692 /* Do we have a loglevel in the string? */
694 unsigned char c
= p
[1];
695 if (c
&& p
[2] == '>') {
697 case '0' ... '7': /* loglevel */
698 current_log_level
= c
- '0';
699 if (!new_text_line
) {
703 /* Fallthrough - skip the loglevel */
704 case 'c': /* KERN_CONT */
712 * Copy the output into log_buf. If the caller didn't provide
713 * appropriate log level tags, we insert them here
717 /* Always output the token */
719 emit_log_char(current_log_level
+ '0');
725 /* Follow the token with the time */
728 unsigned long long t
;
729 unsigned long nanosec_rem
;
731 t
= cpu_clock(printk_cpu
);
732 nanosec_rem
= do_div(t
, 1000000000);
733 tlen
= sprintf(tbuf
, "[%5lu.%06lu] ",
737 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
752 * Try to acquire and then immediately release the
753 * console semaphore. The release will do all the
754 * actual magic (print out buffers, wake up klogd,
757 * The acquire_console_semaphore_for_printk() function
758 * will release 'logbuf_lock' regardless of whether it
759 * actually gets the semaphore or not.
761 if (acquire_console_semaphore_for_printk(this_cpu
))
762 release_console_sem();
766 raw_local_irq_restore(flags
);
771 EXPORT_SYMBOL(printk
);
772 EXPORT_SYMBOL(vprintk
);
776 static void call_console_drivers(unsigned start
, unsigned end
)
782 static int __add_preferred_console(char *name
, int idx
, char *options
,
785 struct console_cmdline
*c
;
789 * See if this tty is not yet registered, and
790 * if we have a slot free.
792 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
793 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
794 console_cmdline
[i
].index
== idx
) {
796 selected_console
= i
;
799 if (i
== MAX_CMDLINECONSOLES
)
802 selected_console
= i
;
803 c
= &console_cmdline
[i
];
804 strlcpy(c
->name
, name
, sizeof(c
->name
));
805 c
->options
= options
;
806 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
807 c
->brl_options
= brl_options
;
813 * Set up a list of consoles. Called from init/main.c
815 static int __init
console_setup(char *str
)
817 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
818 char *s
, *options
, *brl_options
= NULL
;
821 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
822 if (!memcmp(str
, "brl,", 4)) {
825 } else if (!memcmp(str
, "brl=", 4)) {
826 brl_options
= str
+ 4;
827 str
= strchr(brl_options
, ',');
829 printk(KERN_ERR
"need port name after brl=\n");
837 * Decode str into name, index, options.
839 if (str
[0] >= '0' && str
[0] <= '9') {
841 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
843 strncpy(buf
, str
, sizeof(buf
) - 1);
845 buf
[sizeof(buf
) - 1] = 0;
846 if ((options
= strchr(str
, ',')) != NULL
)
849 if (!strcmp(str
, "ttya"))
850 strcpy(buf
, "ttyS0");
851 if (!strcmp(str
, "ttyb"))
852 strcpy(buf
, "ttyS1");
854 for (s
= buf
; *s
; s
++)
855 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
857 idx
= simple_strtoul(s
, NULL
, 10);
860 __add_preferred_console(buf
, idx
, options
, brl_options
);
861 console_set_on_cmdline
= 1;
864 __setup("console=", console_setup
);
867 * add_preferred_console - add a device to the list of preferred consoles.
870 * @options: options for this console
872 * The last preferred console added will be used for kernel messages
873 * and stdin/out/err for init. Normally this is used by console_setup
874 * above to handle user-supplied console arguments; however it can also
875 * be used by arch-specific code either to override the user or more
876 * commonly to provide a default console (ie from PROM variables) when
877 * the user has not supplied one.
879 int add_preferred_console(char *name
, int idx
, char *options
)
881 return __add_preferred_console(name
, idx
, options
, NULL
);
884 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
886 struct console_cmdline
*c
;
889 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
890 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
891 console_cmdline
[i
].index
== idx
) {
892 c
= &console_cmdline
[i
];
893 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
894 c
->name
[sizeof(c
->name
) - 1] = 0;
895 c
->options
= options
;
903 int console_suspend_enabled
= 1;
904 EXPORT_SYMBOL(console_suspend_enabled
);
906 static int __init
console_suspend_disable(char *str
)
908 console_suspend_enabled
= 0;
911 __setup("no_console_suspend", console_suspend_disable
);
914 * suspend_console - suspend the console subsystem
916 * This disables printk() while we go into suspend states
918 void suspend_console(void)
920 if (!console_suspend_enabled
)
922 printk("Suspending console(s) (use no_console_suspend to debug)\n");
923 acquire_console_sem();
924 console_suspended
= 1;
928 void resume_console(void)
930 if (!console_suspend_enabled
)
933 console_suspended
= 0;
934 release_console_sem();
938 * acquire_console_sem - lock the console system for exclusive use.
940 * Acquires a semaphore which guarantees that the caller has
941 * exclusive access to the console system and the console_drivers list.
943 * Can sleep, returns nothing.
945 void acquire_console_sem(void)
947 BUG_ON(in_interrupt());
949 if (console_suspended
)
952 console_may_schedule
= 1;
954 EXPORT_SYMBOL(acquire_console_sem
);
956 int try_acquire_console_sem(void)
958 if (down_trylock(&console_sem
))
960 if (console_suspended
) {
965 console_may_schedule
= 0;
968 EXPORT_SYMBOL(try_acquire_console_sem
);
970 int is_console_locked(void)
972 return console_locked
;
975 static DEFINE_PER_CPU(int, printk_pending
);
977 void printk_tick(void)
979 if (__get_cpu_var(printk_pending
)) {
980 __get_cpu_var(printk_pending
) = 0;
981 wake_up_interruptible(&log_wait
);
985 int printk_needs_cpu(int cpu
)
987 return per_cpu(printk_pending
, cpu
);
990 void wake_up_klogd(void)
992 if (waitqueue_active(&log_wait
))
993 __raw_get_cpu_var(printk_pending
) = 1;
997 * release_console_sem - unlock the console system
999 * Releases the semaphore which the caller holds on the console system
1000 * and the console driver list.
1002 * While the semaphore was held, console output may have been buffered
1003 * by printk(). If this is the case, release_console_sem() emits
1004 * the output prior to releasing the semaphore.
1006 * If there is output waiting for klogd, we wake it up.
1008 * release_console_sem() may be called from any context.
1010 void release_console_sem(void)
1012 unsigned long flags
;
1013 unsigned _con_start
, _log_end
;
1014 unsigned wake_klogd
= 0;
1016 if (console_suspended
) {
1021 console_may_schedule
= 0;
1024 spin_lock_irqsave(&logbuf_lock
, flags
);
1025 wake_klogd
|= log_start
- log_end
;
1026 if (con_start
== log_end
)
1027 break; /* Nothing to print */
1028 _con_start
= con_start
;
1030 con_start
= log_end
; /* Flush */
1031 spin_unlock(&logbuf_lock
);
1032 stop_critical_timings(); /* don't trace print latency */
1033 call_console_drivers(_con_start
, _log_end
);
1034 start_critical_timings();
1035 local_irq_restore(flags
);
1039 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1043 EXPORT_SYMBOL(release_console_sem
);
1046 * console_conditional_schedule - yield the CPU if required
1048 * If the console code is currently allowed to sleep, and
1049 * if this CPU should yield the CPU to another task, do
1052 * Must be called within acquire_console_sem().
1054 void __sched
console_conditional_schedule(void)
1056 if (console_may_schedule
)
1059 EXPORT_SYMBOL(console_conditional_schedule
);
1061 void console_print(const char *s
)
1063 printk(KERN_EMERG
"%s", s
);
1065 EXPORT_SYMBOL(console_print
);
1067 void console_unblank(void)
1072 * console_unblank can no longer be called in interrupt context unless
1073 * oops_in_progress is set to 1..
1075 if (oops_in_progress
) {
1076 if (down_trylock(&console_sem
) != 0)
1079 acquire_console_sem();
1082 console_may_schedule
= 0;
1083 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
)
1084 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
1086 release_console_sem();
1090 * Return the console tty driver structure and its associated index
1092 struct tty_driver
*console_device(int *index
)
1095 struct tty_driver
*driver
= NULL
;
1097 acquire_console_sem();
1098 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
) {
1101 driver
= c
->device(c
, index
);
1105 release_console_sem();
1110 * Prevent further output on the passed console device so that (for example)
1111 * serial drivers can disable console output before suspending a port, and can
1112 * re-enable output afterwards.
1114 void console_stop(struct console
*console
)
1116 acquire_console_sem();
1117 console
->flags
&= ~CON_ENABLED
;
1118 release_console_sem();
1120 EXPORT_SYMBOL(console_stop
);
1122 void console_start(struct console
*console
)
1124 acquire_console_sem();
1125 console
->flags
|= CON_ENABLED
;
1126 release_console_sem();
1128 EXPORT_SYMBOL(console_start
);
1131 * The console driver calls this routine during kernel initialization
1132 * to register the console printing procedure with printk() and to
1133 * print any messages that were printed by the kernel before the
1134 * console driver was initialized.
1136 void register_console(struct console
*console
)
1139 unsigned long flags
;
1140 struct console
*bootconsole
= NULL
;
1142 if (console_drivers
) {
1143 if (console
->flags
& CON_BOOT
)
1145 if (console_drivers
->flags
& CON_BOOT
)
1146 bootconsole
= console_drivers
;
1149 if (preferred_console
< 0 || bootconsole
|| !console_drivers
)
1150 preferred_console
= selected_console
;
1152 if (console
->early_setup
)
1153 console
->early_setup();
1156 * See if we want to use this console driver. If we
1157 * didn't select a console we take the first one
1158 * that registers here.
1160 if (preferred_console
< 0) {
1161 if (console
->index
< 0)
1163 if (console
->setup
== NULL
||
1164 console
->setup(console
, NULL
) == 0) {
1165 console
->flags
|= CON_ENABLED
;
1166 if (console
->device
) {
1167 console
->flags
|= CON_CONSDEV
;
1168 preferred_console
= 0;
1174 * See if this console matches one we selected on
1177 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
1179 if (strcmp(console_cmdline
[i
].name
, console
->name
) != 0)
1181 if (console
->index
>= 0 &&
1182 console
->index
!= console_cmdline
[i
].index
)
1184 if (console
->index
< 0)
1185 console
->index
= console_cmdline
[i
].index
;
1186 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1187 if (console_cmdline
[i
].brl_options
) {
1188 console
->flags
|= CON_BRL
;
1189 braille_register_console(console
,
1190 console_cmdline
[i
].index
,
1191 console_cmdline
[i
].options
,
1192 console_cmdline
[i
].brl_options
);
1196 if (console
->setup
&&
1197 console
->setup(console
, console_cmdline
[i
].options
) != 0)
1199 console
->flags
|= CON_ENABLED
;
1200 console
->index
= console_cmdline
[i
].index
;
1201 if (i
== selected_console
) {
1202 console
->flags
|= CON_CONSDEV
;
1203 preferred_console
= selected_console
;
1208 if (!(console
->flags
& CON_ENABLED
))
1211 if (bootconsole
&& (console
->flags
& CON_CONSDEV
)) {
1212 printk(KERN_INFO
"console handover: boot [%s%d] -> real [%s%d]\n",
1213 bootconsole
->name
, bootconsole
->index
,
1214 console
->name
, console
->index
);
1215 unregister_console(bootconsole
);
1216 console
->flags
&= ~CON_PRINTBUFFER
;
1218 printk(KERN_INFO
"console [%s%d] enabled\n",
1219 console
->name
, console
->index
);
1223 * Put this console in the list - keep the
1224 * preferred driver at the head of the list.
1226 acquire_console_sem();
1227 if ((console
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
1228 console
->next
= console_drivers
;
1229 console_drivers
= console
;
1231 console
->next
->flags
&= ~CON_CONSDEV
;
1233 console
->next
= console_drivers
->next
;
1234 console_drivers
->next
= console
;
1236 if (console
->flags
& CON_PRINTBUFFER
) {
1238 * release_console_sem() will print out the buffered messages
1241 spin_lock_irqsave(&logbuf_lock
, flags
);
1242 con_start
= log_start
;
1243 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1245 release_console_sem();
1247 EXPORT_SYMBOL(register_console
);
1249 int unregister_console(struct console
*console
)
1251 struct console
*a
, *b
;
1254 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1255 if (console
->flags
& CON_BRL
)
1256 return braille_unregister_console(console
);
1259 acquire_console_sem();
1260 if (console_drivers
== console
) {
1261 console_drivers
=console
->next
;
1263 } else if (console_drivers
) {
1264 for (a
=console_drivers
->next
, b
=console_drivers
;
1265 a
; b
=a
, a
=b
->next
) {
1275 * If this isn't the last console and it has CON_CONSDEV set, we
1276 * need to set it on the next preferred console.
1278 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
1279 console_drivers
->flags
|= CON_CONSDEV
;
1281 release_console_sem();
1284 EXPORT_SYMBOL(unregister_console
);
1286 static int __init
disable_boot_consoles(void)
1288 if (console_drivers
!= NULL
) {
1289 if (console_drivers
->flags
& CON_BOOT
) {
1290 printk(KERN_INFO
"turn off boot console %s%d\n",
1291 console_drivers
->name
, console_drivers
->index
);
1292 return unregister_console(console_drivers
);
1297 late_initcall(disable_boot_consoles
);
1299 #if defined CONFIG_PRINTK
1302 * printk rate limiting, lifted from the networking subsystem.
1304 * This enforces a rate limit: not more than 10 kernel messages
1305 * every 5s to make a denial-of-service attack impossible.
1307 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
1309 int printk_ratelimit(void)
1311 return __ratelimit(&printk_ratelimit_state
);
1313 EXPORT_SYMBOL(printk_ratelimit
);
1316 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1317 * @caller_jiffies: pointer to caller's state
1318 * @interval_msecs: minimum interval between prints
1320 * printk_timed_ratelimit() returns true if more than @interval_msecs
1321 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1324 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
1325 unsigned int interval_msecs
)
1327 if (*caller_jiffies
== 0
1328 || !time_in_range(jiffies
, *caller_jiffies
,
1330 + msecs_to_jiffies(interval_msecs
))) {
1331 *caller_jiffies
= jiffies
;
1336 EXPORT_SYMBOL(printk_timed_ratelimit
);