[PATCH] fix vmstat per cpu usage
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / kernel / printk.c
CommitLineData
1da177e4
LT
1/*
2 * linux/kernel/printk.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
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).
11 * Ted Ts'o, 2/11/93.
12 * Modified for sysctl support, 1/8/97, Chris Horn.
40dc5651 13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
624dffcb 14 * manfred@colorfullife.com
1da177e4
LT
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton <andrewm@uow.edu.au>
17 */
18
19#include <linux/kernel.h>
20#include <linux/mm.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>
3b9c0410 27#include <linux/moduleparam.h>
1da177e4 28#include <linux/interrupt.h> /* For in_interrupt() */
1da177e4
LT
29#include <linux/delay.h>
30#include <linux/smp.h>
31#include <linux/security.h>
32#include <linux/bootmem.h>
33#include <linux/syscalls.h>
34
35#include <asm/uaccess.h>
36
37#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
38
39/* printk's without a loglevel use this.. */
40#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
41
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 */
45
46DECLARE_WAIT_QUEUE_HEAD(log_wait);
47
48int 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 */
53};
54
c0fc84d2 55EXPORT_UNUSED_SYMBOL(console_printk); /* June 2006 */
1da177e4
LT
56
57/*
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.
60 */
61int oops_in_progress;
62EXPORT_SYMBOL(oops_in_progress);
63
64/*
65 * console_sem protects the console_drivers list, and also
66 * provides serialisation for access to the entire console
67 * driver system.
68 */
69static DECLARE_MUTEX(console_sem);
557240b4 70static DECLARE_MUTEX(secondary_console_sem);
1da177e4
LT
71struct console *console_drivers;
72/*
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
79 */
557240b4 80static int console_locked, console_suspended;
1da177e4
LT
81
82/*
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().
86 */
87static DEFINE_SPINLOCK(logbuf_lock);
88
1da177e4
LT
89#define LOG_BUF_MASK (log_buf_len-1)
90#define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
91
92/*
93 * The indices into log_buf are not constrained to log_buf_len - they
94 * must be masked before subscripting
95 */
96static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
97static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
98static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */
1da177e4
LT
99
100/*
101 * Array of consoles built from command line options (console=)
102 */
103struct console_cmdline
104{
105 char name[8]; /* Name of the driver */
106 int index; /* Minor dev. to use */
107 char *options; /* Options for the driver */
108};
109
110#define MAX_CMDLINECONSOLES 8
111
112static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
113static int selected_console = -1;
114static int preferred_console = -1;
115
116/* Flag: console code may call schedule() */
117static int console_may_schedule;
118
d59745ce
MM
119#ifdef CONFIG_PRINTK
120
121static char __log_buf[__LOG_BUF_LEN];
122static char *log_buf = __log_buf;
123static int log_buf_len = __LOG_BUF_LEN;
124static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
125
1da177e4
LT
126static int __init log_buf_len_setup(char *str)
127{
128 unsigned long size = memparse(str, &str);
129 unsigned long flags;
130
131 if (size)
132 size = roundup_pow_of_two(size);
133 if (size > log_buf_len) {
134 unsigned long start, dest_idx, offset;
40dc5651 135 char *new_log_buf;
1da177e4
LT
136
137 new_log_buf = alloc_bootmem(size);
138 if (!new_log_buf) {
40dc5651 139 printk(KERN_WARNING "log_buf_len: allocation failed\n");
1da177e4
LT
140 goto out;
141 }
142
143 spin_lock_irqsave(&logbuf_lock, flags);
144 log_buf_len = size;
145 log_buf = new_log_buf;
146
147 offset = start = min(con_start, log_start);
148 dest_idx = 0;
149 while (start != log_end) {
150 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
151 start++;
152 dest_idx++;
153 }
154 log_start -= offset;
155 con_start -= offset;
156 log_end -= offset;
157 spin_unlock_irqrestore(&logbuf_lock, flags);
158
40dc5651 159 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
1da177e4
LT
160 }
161out:
1da177e4
LT
162 return 1;
163}
164
165__setup("log_buf_len=", log_buf_len_setup);
166
167/*
168 * Commands to do_syslog:
169 *
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
181 */
40dc5651 182int do_syslog(int type, char __user *buf, int len)
1da177e4
LT
183{
184 unsigned long i, j, limit, count;
185 int do_clear = 0;
186 char c;
187 int error = 0;
188
189 error = security_syslog(type);
190 if (error)
191 return error;
192
193 switch (type) {
194 case 0: /* Close log */
195 break;
196 case 1: /* Open log */
197 break;
198 case 2: /* Read from log */
199 error = -EINVAL;
200 if (!buf || len < 0)
201 goto out;
202 error = 0;
203 if (!len)
204 goto out;
205 if (!access_ok(VERIFY_WRITE, buf, len)) {
206 error = -EFAULT;
207 goto out;
208 }
40dc5651
JJ
209 error = wait_event_interruptible(log_wait,
210 (log_start - log_end));
1da177e4
LT
211 if (error)
212 goto out;
213 i = 0;
214 spin_lock_irq(&logbuf_lock);
215 while (!error && (log_start != log_end) && i < len) {
216 c = LOG_BUF(log_start);
217 log_start++;
218 spin_unlock_irq(&logbuf_lock);
219 error = __put_user(c,buf);
220 buf++;
221 i++;
222 cond_resched();
223 spin_lock_irq(&logbuf_lock);
224 }
225 spin_unlock_irq(&logbuf_lock);
226 if (!error)
227 error = i;
228 break;
229 case 4: /* Read/clear last kernel messages */
40dc5651 230 do_clear = 1;
1da177e4
LT
231 /* FALL THRU */
232 case 3: /* Read last kernel messages */
233 error = -EINVAL;
234 if (!buf || len < 0)
235 goto out;
236 error = 0;
237 if (!len)
238 goto out;
239 if (!access_ok(VERIFY_WRITE, buf, len)) {
240 error = -EFAULT;
241 goto out;
242 }
243 count = len;
244 if (count > log_buf_len)
245 count = log_buf_len;
246 spin_lock_irq(&logbuf_lock);
247 if (count > logged_chars)
248 count = logged_chars;
249 if (do_clear)
250 logged_chars = 0;
251 limit = log_end;
252 /*
253 * __put_user() could sleep, and while we sleep
40dc5651 254 * printk() could overwrite the messages
1da177e4
LT
255 * we try to copy to user space. Therefore
256 * the messages are copied in reverse. <manfreds>
257 */
40dc5651 258 for (i = 0; i < count && !error; i++) {
1da177e4
LT
259 j = limit-1-i;
260 if (j + log_buf_len < log_end)
261 break;
262 c = LOG_BUF(j);
263 spin_unlock_irq(&logbuf_lock);
264 error = __put_user(c,&buf[count-1-i]);
265 cond_resched();
266 spin_lock_irq(&logbuf_lock);
267 }
268 spin_unlock_irq(&logbuf_lock);
269 if (error)
270 break;
271 error = i;
40dc5651 272 if (i != count) {
1da177e4
LT
273 int offset = count-error;
274 /* buffer overflow during copy, correct user buffer. */
40dc5651 275 for (i = 0; i < error; i++) {
1da177e4
LT
276 if (__get_user(c,&buf[i+offset]) ||
277 __put_user(c,&buf[i])) {
278 error = -EFAULT;
279 break;
280 }
281 cond_resched();
282 }
283 }
284 break;
285 case 5: /* Clear ring buffer */
286 logged_chars = 0;
287 break;
288 case 6: /* Disable logging to console */
289 console_loglevel = minimum_console_loglevel;
290 break;
291 case 7: /* Enable logging to console */
292 console_loglevel = default_console_loglevel;
293 break;
294 case 8: /* Set level of messages printed to console */
295 error = -EINVAL;
296 if (len < 1 || len > 8)
297 goto out;
298 if (len < minimum_console_loglevel)
299 len = minimum_console_loglevel;
300 console_loglevel = len;
301 error = 0;
302 break;
303 case 9: /* Number of chars in the log buffer */
304 error = log_end - log_start;
305 break;
306 case 10: /* Size of the log buffer */
307 error = log_buf_len;
308 break;
309 default:
310 error = -EINVAL;
311 break;
312 }
313out:
314 return error;
315}
316
40dc5651 317asmlinkage long sys_syslog(int type, char __user *buf, int len)
1da177e4
LT
318{
319 return do_syslog(type, buf, len);
320}
321
322/*
323 * Call the console drivers on a range of log_buf
324 */
325static void __call_console_drivers(unsigned long start, unsigned long end)
326{
327 struct console *con;
328
329 for (con = console_drivers; con; con = con->next) {
76a8ad29
ME
330 if ((con->flags & CON_ENABLED) && con->write &&
331 (cpu_online(smp_processor_id()) ||
332 (con->flags & CON_ANYTIME)))
1da177e4
LT
333 con->write(con, &LOG_BUF(start), end - start);
334 }
335}
336
337/*
338 * Write out chars from start to end - 1 inclusive
339 */
340static void _call_console_drivers(unsigned long start,
341 unsigned long end, int msg_log_level)
342{
343 if (msg_log_level < console_loglevel &&
344 console_drivers && start != end) {
345 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
346 /* wrapped write */
347 __call_console_drivers(start & LOG_BUF_MASK,
348 log_buf_len);
349 __call_console_drivers(0, end & LOG_BUF_MASK);
350 } else {
351 __call_console_drivers(start, end);
352 }
353 }
354}
355
356/*
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.
360 */
361static void call_console_drivers(unsigned long start, unsigned long end)
362{
363 unsigned long cur_index, start_print;
364 static int msg_level = -1;
365
8abd8e29 366 BUG_ON(((long)(start - end)) > 0);
1da177e4
LT
367
368 cur_index = start;
369 start_print = start;
370 while (cur_index != end) {
40dc5651
JJ
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) == '>') {
1da177e4
LT
376 msg_level = LOG_BUF(cur_index + 1) - '0';
377 cur_index += 3;
378 start_print = cur_index;
379 }
380 while (cur_index != end) {
381 char c = LOG_BUF(cur_index);
1da177e4 382
40dc5651 383 cur_index++;
1da177e4
LT
384 if (c == '\n') {
385 if (msg_level < 0) {
386 /*
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
390 * on those tags
391 */
392 msg_level = default_message_loglevel;
393 }
394 _call_console_drivers(start_print, cur_index, msg_level);
395 msg_level = -1;
396 start_print = cur_index;
397 break;
398 }
399 }
400 }
401 _call_console_drivers(start_print, end, msg_level);
402}
403
404static void emit_log_char(char c)
405{
406 LOG_BUF(log_end) = c;
407 log_end++;
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)
413 logged_chars++;
414}
415
416/*
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
419 * full oops.
420 */
421static void zap_locks(void)
422{
423 static unsigned long oops_timestamp;
424
425 if (time_after_eq(jiffies, oops_timestamp) &&
40dc5651 426 !time_after(jiffies, oops_timestamp + 30 * HZ))
1da177e4
LT
427 return;
428
429 oops_timestamp = jiffies;
430
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);
435}
436
437#if defined(CONFIG_PRINTK_TIME)
438static int printk_time = 1;
439#else
440static int printk_time = 0;
441#endif
3b9c0410 442module_param(printk_time, int, S_IRUGO | S_IWUSR);
1da177e4
LT
443
444static int __init printk_time_setup(char *str)
445{
446 if (*str)
447 return 0;
448 printk_time = 1;
449 return 1;
450}
451
452__setup("time", printk_time_setup);
453
31f6d9d6
AM
454__attribute__((weak)) unsigned long long printk_clock(void)
455{
456 return sched_clock();
457}
458
76a8ad29
ME
459/* Check if we have any console registered that can be called early in boot. */
460static int have_callable_console(void)
461{
462 struct console *con;
463
464 for (con = console_drivers; con; con = con->next)
465 if (con->flags & CON_ANYTIME)
466 return 1;
467
468 return 0;
469}
470
ddad86c2
MW
471/**
472 * printk - print a kernel message
473 * @fmt: format string
474 *
1da177e4 475 * This is printk. It can be called from any context. We want it to work.
40dc5651 476 *
1da177e4
LT
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.
482 *
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.
ddad86c2
MW
486 *
487 * See also:
488 * printf(3)
1da177e4 489 */
d59745ce 490
1da177e4
LT
491asmlinkage int printk(const char *fmt, ...)
492{
493 va_list args;
494 int r;
495
496 va_start(args, fmt);
497 r = vprintk(fmt, args);
498 va_end(args);
499
500 return r;
501}
502
fe21773d
DH
503/* cpu currently holding logbuf_lock */
504static volatile unsigned int printk_cpu = UINT_MAX;
505
1da177e4
LT
506asmlinkage int vprintk(const char *fmt, va_list args)
507{
508 unsigned long flags;
509 int printed_len;
510 char *p;
511 static char printk_buf[1024];
512 static int log_level_unknown = 1;
513
fe21773d
DH
514 preempt_disable();
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 */
1da177e4
LT
518 zap_locks();
519
520 /* This stops the holder of console_sem just where we want him */
a0f1ccfd
IM
521 local_irq_save(flags);
522 lockdep_off();
523 spin_lock(&logbuf_lock);
fe21773d 524 printk_cpu = smp_processor_id();
1da177e4
LT
525
526 /* Emit the output into the temporary buffer */
527 printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
528
529 /*
530 * Copy the output into log_buf. If the caller didn't provide
531 * appropriate log level tags, we insert them here
532 */
533 for (p = printk_buf; *p; p++) {
534 if (log_level_unknown) {
535 /* log_level_unknown signals the start of a new line */
536 if (printk_time) {
537 int loglev_char;
538 char tbuf[50], *tp;
539 unsigned tlen;
540 unsigned long long t;
541 unsigned long nanosec_rem;
542
543 /*
544 * force the log level token to be
545 * before the time output.
546 */
547 if (p[0] == '<' && p[1] >='0' &&
548 p[1] <= '7' && p[2] == '>') {
549 loglev_char = p[1];
550 p += 3;
025510cd 551 printed_len -= 3;
1da177e4
LT
552 } else {
553 loglev_char = default_message_loglevel
554 + '0';
555 }
31f6d9d6 556 t = printk_clock();
1da177e4
LT
557 nanosec_rem = do_div(t, 1000000000);
558 tlen = sprintf(tbuf,
559 "<%c>[%5lu.%06lu] ",
560 loglev_char,
561 (unsigned long)t,
562 nanosec_rem/1000);
563
564 for (tp = tbuf; tp < tbuf + tlen; tp++)
565 emit_log_char(*tp);
025510cd 566 printed_len += tlen;
1da177e4
LT
567 } else {
568 if (p[0] != '<' || p[1] < '0' ||
569 p[1] > '7' || p[2] != '>') {
570 emit_log_char('<');
571 emit_log_char(default_message_loglevel
572 + '0');
573 emit_log_char('>');
025510cd 574 printed_len += 3;
1da177e4 575 }
1da177e4
LT
576 }
577 log_level_unknown = 0;
578 if (!*p)
579 break;
580 }
581 emit_log_char(*p);
582 if (*p == '\n')
583 log_level_unknown = 1;
584 }
585
76a8ad29 586 if (!down_trylock(&console_sem)) {
1da177e4 587 /*
76a8ad29
ME
588 * We own the drivers. We can drop the spinlock and
589 * let release_console_sem() print the text, maybe ...
1da177e4 590 */
76a8ad29 591 console_locked = 1;
fe21773d 592 printk_cpu = UINT_MAX;
a0f1ccfd 593 spin_unlock(&logbuf_lock);
76a8ad29 594
1da177e4 595 /*
76a8ad29
ME
596 * Console drivers may assume that per-cpu resources have
597 * been allocated. So unless they're explicitly marked as
598 * being able to cope (CON_ANYTIME) don't call them until
599 * this CPU is officially up.
1da177e4 600 */
76a8ad29
ME
601 if (cpu_online(smp_processor_id()) || have_callable_console()) {
602 console_may_schedule = 0;
603 release_console_sem();
604 } else {
605 /* Release by hand to avoid flushing the buffer. */
606 console_locked = 0;
607 up(&console_sem);
608 }
a0f1ccfd
IM
609 lockdep_on();
610 local_irq_restore(flags);
1da177e4
LT
611 } else {
612 /*
613 * Someone else owns the drivers. We drop the spinlock, which
614 * allows the semaphore holder to proceed and to call the
615 * console drivers with the output which we just produced.
616 */
fe21773d 617 printk_cpu = UINT_MAX;
a0f1ccfd
IM
618 spin_unlock(&logbuf_lock);
619 lockdep_on();
620 local_irq_restore(flags);
1da177e4 621 }
76a8ad29 622
fe21773d 623 preempt_enable();
1da177e4
LT
624 return printed_len;
625}
626EXPORT_SYMBOL(printk);
627EXPORT_SYMBOL(vprintk);
628
d59745ce
MM
629#else
630
40dc5651 631asmlinkage long sys_syslog(int type, char __user *buf, int len)
d59745ce
MM
632{
633 return 0;
634}
635
40dc5651
JJ
636int do_syslog(int type, char __user *buf, int len)
637{
638 return 0;
639}
640
641static void call_console_drivers(unsigned long start, unsigned long end)
642{
643}
d59745ce
MM
644
645#endif
646
2ea1c539
JB
647/*
648 * Set up a list of consoles. Called from init/main.c
649 */
650static int __init console_setup(char *str)
651{
652 char name[sizeof(console_cmdline[0].name)];
653 char *s, *options;
654 int idx;
655
656 /*
657 * Decode str into name, index, options.
658 */
659 if (str[0] >= '0' && str[0] <= '9') {
660 strcpy(name, "ttyS");
661 strncpy(name + 4, str, sizeof(name) - 5);
662 } else {
663 strncpy(name, str, sizeof(name) - 1);
664 }
665 name[sizeof(name) - 1] = 0;
666 if ((options = strchr(str, ',')) != NULL)
667 *(options++) = 0;
668#ifdef __sparc__
669 if (!strcmp(str, "ttya"))
670 strcpy(name, "ttyS0");
671 if (!strcmp(str, "ttyb"))
672 strcpy(name, "ttyS1");
673#endif
674 for (s = name; *s; s++)
675 if ((*s >= '0' && *s <= '9') || *s == ',')
676 break;
677 idx = simple_strtoul(s, NULL, 10);
678 *s = 0;
679
680 add_preferred_console(name, idx, options);
681 return 1;
682}
683__setup("console=", console_setup);
684
3c0547ba
MM
685/**
686 * add_preferred_console - add a device to the list of preferred consoles.
ddad86c2
MW
687 * @name: device name
688 * @idx: device index
689 * @options: options for this console
3c0547ba
MM
690 *
691 * The last preferred console added will be used for kernel messages
692 * and stdin/out/err for init. Normally this is used by console_setup
693 * above to handle user-supplied console arguments; however it can also
694 * be used by arch-specific code either to override the user or more
695 * commonly to provide a default console (ie from PROM variables) when
696 * the user has not supplied one.
697 */
698int __init add_preferred_console(char *name, int idx, char *options)
699{
700 struct console_cmdline *c;
701 int i;
702
703 /*
704 * See if this tty is not yet registered, and
705 * if we have a slot free.
706 */
707 for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
708 if (strcmp(console_cmdline[i].name, name) == 0 &&
709 console_cmdline[i].index == idx) {
710 selected_console = i;
711 return 0;
712 }
713 if (i == MAX_CMDLINECONSOLES)
714 return -E2BIG;
715 selected_console = i;
716 c = &console_cmdline[i];
717 memcpy(c->name, name, sizeof(c->name));
718 c->name[sizeof(c->name) - 1] = 0;
719 c->options = options;
720 c->index = idx;
721 return 0;
722}
723
557240b4
LT
724/**
725 * suspend_console - suspend the console subsystem
726 *
727 * This disables printk() while we go into suspend states
728 */
729void suspend_console(void)
730{
731 acquire_console_sem();
732 console_suspended = 1;
733}
734
735void resume_console(void)
736{
737 console_suspended = 0;
738 release_console_sem();
739}
740
1da177e4
LT
741/**
742 * acquire_console_sem - lock the console system for exclusive use.
743 *
744 * Acquires a semaphore which guarantees that the caller has
745 * exclusive access to the console system and the console_drivers list.
746 *
747 * Can sleep, returns nothing.
748 */
749void acquire_console_sem(void)
750{
8abd8e29 751 BUG_ON(in_interrupt());
557240b4
LT
752 if (console_suspended) {
753 down(&secondary_console_sem);
754 return;
755 }
1da177e4
LT
756 down(&console_sem);
757 console_locked = 1;
758 console_may_schedule = 1;
759}
760EXPORT_SYMBOL(acquire_console_sem);
761
762int try_acquire_console_sem(void)
763{
764 if (down_trylock(&console_sem))
765 return -1;
766 console_locked = 1;
767 console_may_schedule = 0;
768 return 0;
769}
770EXPORT_SYMBOL(try_acquire_console_sem);
771
772int is_console_locked(void)
773{
774 return console_locked;
775}
c0fc84d2 776EXPORT_UNUSED_SYMBOL(is_console_locked); /* June 2006 */
1da177e4
LT
777
778/**
779 * release_console_sem - unlock the console system
780 *
781 * Releases the semaphore which the caller holds on the console system
782 * and the console driver list.
783 *
784 * While the semaphore was held, console output may have been buffered
785 * by printk(). If this is the case, release_console_sem() emits
786 * the output prior to releasing the semaphore.
787 *
788 * If there is output waiting for klogd, we wake it up.
789 *
790 * release_console_sem() may be called from any context.
791 */
792void release_console_sem(void)
793{
794 unsigned long flags;
795 unsigned long _con_start, _log_end;
796 unsigned long wake_klogd = 0;
797
557240b4
LT
798 if (console_suspended) {
799 up(&secondary_console_sem);
800 return;
801 }
1da177e4
LT
802 for ( ; ; ) {
803 spin_lock_irqsave(&logbuf_lock, flags);
804 wake_klogd |= log_start - log_end;
805 if (con_start == log_end)
806 break; /* Nothing to print */
807 _con_start = con_start;
808 _log_end = log_end;
809 con_start = log_end; /* Flush */
810 spin_unlock(&logbuf_lock);
811 call_console_drivers(_con_start, _log_end);
812 local_irq_restore(flags);
813 }
814 console_locked = 0;
815 console_may_schedule = 0;
816 up(&console_sem);
817 spin_unlock_irqrestore(&logbuf_lock, flags);
a0f1ccfd
IM
818 if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) {
819 /*
820 * If we printk from within the lock dependency code,
821 * from within the scheduler code, then do not lock
822 * up due to self-recursion:
823 */
824 if (!lockdep_internal())
825 wake_up_interruptible(&log_wait);
826 }
1da177e4
LT
827}
828EXPORT_SYMBOL(release_console_sem);
829
ddad86c2
MW
830/**
831 * console_conditional_schedule - yield the CPU if required
1da177e4
LT
832 *
833 * If the console code is currently allowed to sleep, and
834 * if this CPU should yield the CPU to another task, do
835 * so here.
836 *
837 * Must be called within acquire_console_sem().
838 */
839void __sched console_conditional_schedule(void)
840{
841 if (console_may_schedule)
842 cond_resched();
843}
844EXPORT_SYMBOL(console_conditional_schedule);
845
846void console_print(const char *s)
847{
848 printk(KERN_EMERG "%s", s);
849}
850EXPORT_SYMBOL(console_print);
851
852void console_unblank(void)
853{
854 struct console *c;
855
856 /*
857 * console_unblank can no longer be called in interrupt context unless
858 * oops_in_progress is set to 1..
859 */
860 if (oops_in_progress) {
861 if (down_trylock(&console_sem) != 0)
862 return;
863 } else
864 acquire_console_sem();
865
866 console_locked = 1;
867 console_may_schedule = 0;
868 for (c = console_drivers; c != NULL; c = c->next)
869 if ((c->flags & CON_ENABLED) && c->unblank)
870 c->unblank();
871 release_console_sem();
872}
1da177e4
LT
873
874/*
875 * Return the console tty driver structure and its associated index
876 */
877struct tty_driver *console_device(int *index)
878{
879 struct console *c;
880 struct tty_driver *driver = NULL;
881
882 acquire_console_sem();
883 for (c = console_drivers; c != NULL; c = c->next) {
884 if (!c->device)
885 continue;
886 driver = c->device(c, index);
887 if (driver)
888 break;
889 }
890 release_console_sem();
891 return driver;
892}
893
894/*
895 * Prevent further output on the passed console device so that (for example)
896 * serial drivers can disable console output before suspending a port, and can
897 * re-enable output afterwards.
898 */
899void console_stop(struct console *console)
900{
901 acquire_console_sem();
902 console->flags &= ~CON_ENABLED;
903 release_console_sem();
904}
905EXPORT_SYMBOL(console_stop);
906
907void console_start(struct console *console)
908{
909 acquire_console_sem();
910 console->flags |= CON_ENABLED;
911 release_console_sem();
912}
913EXPORT_SYMBOL(console_start);
914
915/*
916 * The console driver calls this routine during kernel initialization
917 * to register the console printing procedure with printk() and to
918 * print any messages that were printed by the kernel before the
919 * console driver was initialized.
920 */
40dc5651 921void register_console(struct console *console)
1da177e4 922{
40dc5651 923 int i;
1da177e4
LT
924 unsigned long flags;
925
926 if (preferred_console < 0)
927 preferred_console = selected_console;
928
929 /*
930 * See if we want to use this console driver. If we
931 * didn't select a console we take the first one
932 * that registers here.
933 */
934 if (preferred_console < 0) {
935 if (console->index < 0)
936 console->index = 0;
937 if (console->setup == NULL ||
938 console->setup(console, NULL) == 0) {
939 console->flags |= CON_ENABLED | CON_CONSDEV;
940 preferred_console = 0;
941 }
942 }
943
944 /*
945 * See if this console matches one we selected on
946 * the command line.
947 */
40dc5651
JJ
948 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
949 i++) {
1da177e4
LT
950 if (strcmp(console_cmdline[i].name, console->name) != 0)
951 continue;
952 if (console->index >= 0 &&
953 console->index != console_cmdline[i].index)
954 continue;
955 if (console->index < 0)
956 console->index = console_cmdline[i].index;
957 if (console->setup &&
958 console->setup(console, console_cmdline[i].options) != 0)
959 break;
960 console->flags |= CON_ENABLED;
961 console->index = console_cmdline[i].index;
ab4af03a 962 if (i == selected_console) {
1da177e4 963 console->flags |= CON_CONSDEV;
ab4af03a
GE
964 preferred_console = selected_console;
965 }
1da177e4
LT
966 break;
967 }
968
969 if (!(console->flags & CON_ENABLED))
970 return;
971
972 if (console_drivers && (console_drivers->flags & CON_BOOT)) {
973 unregister_console(console_drivers);
974 console->flags &= ~CON_PRINTBUFFER;
975 }
976
977 /*
978 * Put this console in the list - keep the
979 * preferred driver at the head of the list.
980 */
981 acquire_console_sem();
982 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
983 console->next = console_drivers;
984 console_drivers = console;
ab4af03a
GE
985 if (console->next)
986 console->next->flags &= ~CON_CONSDEV;
1da177e4
LT
987 } else {
988 console->next = console_drivers->next;
989 console_drivers->next = console;
990 }
991 if (console->flags & CON_PRINTBUFFER) {
992 /*
993 * release_console_sem() will print out the buffered messages
994 * for us.
995 */
996 spin_lock_irqsave(&logbuf_lock, flags);
997 con_start = log_start;
998 spin_unlock_irqrestore(&logbuf_lock, flags);
999 }
1000 release_console_sem();
1001}
1002EXPORT_SYMBOL(register_console);
1003
40dc5651 1004int unregister_console(struct console *console)
1da177e4 1005{
40dc5651 1006 struct console *a, *b;
1da177e4
LT
1007 int res = 1;
1008
1009 acquire_console_sem();
1010 if (console_drivers == console) {
1011 console_drivers=console->next;
1012 res = 0;
e9b15b54 1013 } else if (console_drivers) {
1da177e4
LT
1014 for (a=console_drivers->next, b=console_drivers ;
1015 a; b=a, a=b->next) {
1016 if (a == console) {
1017 b->next = a->next;
1018 res = 0;
1019 break;
40dc5651 1020 }
1da177e4
LT
1021 }
1022 }
40dc5651 1023
1da177e4
LT
1024 /* If last console is removed, we re-enable picking the first
1025 * one that gets registered. Without that, pmac early boot console
1026 * would prevent fbcon from taking over.
ab4af03a
GE
1027 *
1028 * If this isn't the last console and it has CON_CONSDEV set, we
1029 * need to set it on the next preferred console.
1da177e4
LT
1030 */
1031 if (console_drivers == NULL)
1032 preferred_console = selected_console;
ab4af03a
GE
1033 else if (console->flags & CON_CONSDEV)
1034 console_drivers->flags |= CON_CONSDEV;
1da177e4
LT
1035
1036 release_console_sem();
1037 return res;
1038}
1039EXPORT_SYMBOL(unregister_console);
d59745ce 1040
1da177e4
LT
1041/**
1042 * tty_write_message - write a message to a certain tty, not just the console.
ddad86c2
MW
1043 * @tty: the destination tty_struct
1044 * @msg: the message to write
1da177e4
LT
1045 *
1046 * This is used for messages that need to be redirected to a specific tty.
1047 * We don't put it into the syslog queue right now maybe in the future if
1048 * really needed.
1049 */
1050void tty_write_message(struct tty_struct *tty, char *msg)
1051{
1052 if (tty && tty->driver->write)
1053 tty->driver->write(tty, msg, strlen(msg));
1054 return;
1055}
1056
1057/*
1058 * printk rate limiting, lifted from the networking subsystem.
1059 *
1060 * This enforces a rate limit: not more than one kernel message
1061 * every printk_ratelimit_jiffies to make a denial-of-service
1062 * attack impossible.
1063 */
1064int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1065{
1066 static DEFINE_SPINLOCK(ratelimit_lock);
40dc5651 1067 static unsigned long toks = 10 * 5 * HZ;
1da177e4
LT
1068 static unsigned long last_msg;
1069 static int missed;
1070 unsigned long flags;
1071 unsigned long now = jiffies;
1072
1073 spin_lock_irqsave(&ratelimit_lock, flags);
1074 toks += now - last_msg;
1075 last_msg = now;
1076 if (toks > (ratelimit_burst * ratelimit_jiffies))
1077 toks = ratelimit_burst * ratelimit_jiffies;
1078 if (toks >= ratelimit_jiffies) {
1079 int lost = missed;
40dc5651 1080
1da177e4
LT
1081 missed = 0;
1082 toks -= ratelimit_jiffies;
1083 spin_unlock_irqrestore(&ratelimit_lock, flags);
1084 if (lost)
1085 printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1086 return 1;
1087 }
1088 missed++;
1089 spin_unlock_irqrestore(&ratelimit_lock, flags);
1090 return 0;
1091}
1092EXPORT_SYMBOL(__printk_ratelimit);
1093
1094/* minimum time in jiffies between messages */
40dc5651 1095int printk_ratelimit_jiffies = 5 * HZ;
1da177e4
LT
1096
1097/* number of messages we send before ratelimiting */
1098int printk_ratelimit_burst = 10;
1099
1100int printk_ratelimit(void)
1101{
1102 return __printk_ratelimit(printk_ratelimit_jiffies,
1103 printk_ratelimit_burst);
1104}
1105EXPORT_SYMBOL(printk_ratelimit);