Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 996 insertions, 0 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
new file mode 100644
index 000000000000..1498689548d1
--- /dev/null
+++ b/kernel/printk.c
@@ -0,0 +1,996 @@
+/*
+ *  linux/kernel/printk.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ * Modified to make sys_syslog() more flexible: added commands to
+ * return the last 4k of kernel messages, regardless of whether
+ * they've been read or not.  Added option to suppress kernel printk's
+ * to the console.  Added hook for sending the console messages
+ * elsewhere, in preparation for a serial line console (someday).
+ * Ted Ts'o, 2/11/93.
+ * Modified for sysctl support, 1/8/97, Chris Horn.
+ * Fixed SMP synchronization, 08/08/99, Manfred Spraul 
+ *     manfreds@colorfullife.com
+ * Rewrote bits to get rid of console_lock
+ *      01Mar01 Andrew Morton <andrewm@uow.edu.au>
+ */
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/smp_lock.h>
+#include <linux/console.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>                    /* For in_interrupt() */
+#include <linux/config.h>
+#include <linux/delay.h>
+#include <linux/smp.h>
+#include <linux/security.h>
+#include <linux/bootmem.h>
+#include <linux/syscalls.h>
+
+#include <asm/uaccess.h>
+
+#define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
+
+/* printk's without a loglevel use this.. */
+#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
+
+/* We show everything that is MORE important than this.. */
+#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
+#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
+
+DECLARE_WAIT_QUEUE_HEAD(log_wait);
+
+int console_printk[4] = {
+        DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
+        DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
+        MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
+        DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
+};
+
+EXPORT_SYMBOL(console_printk);
+
+/*
+ * Low lever drivers may need that to know if they can schedule in
+ * their unblank() callback or not. So let's export it.
+ */
+int oops_in_progress;
+EXPORT_SYMBOL(oops_in_progress);
+
+/*
+ * console_sem protects the console_drivers list, and also
+ * provides serialisation for access to the entire console
+ * driver system.
+ */
+static DECLARE_MUTEX(console_sem);
+struct console *console_drivers;
+/*
+ * This is used for debugging the mess that is the VT code by
+ * keeping track if we have the console semaphore held. It's
+ * definitely not the perfect debug tool (we don't know if _WE_
+ * hold it are racing, but it helps tracking those weird code
+ * path in the console code where we end up in places I want
+ * locked without the console sempahore held
+ */
+static int console_locked;
+
+/*
+ * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
+ * It is also used in interesting ways to provide interlocking in
+ * release_console_sem().
+ */
+static DEFINE_SPINLOCK(logbuf_lock);
+
+static char __log_buf[__LOG_BUF_LEN];
+static char *log_buf = __log_buf;
+static int log_buf_len = __LOG_BUF_LEN;
+
+#define LOG_BUF_MASK    (log_buf_len-1)
+#define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
+
+/*
+ * The indices into log_buf are not constrained to log_buf_len - they
+ * must be masked before subscripting
+ */
+static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
+static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
+static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
+static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
+
+/*
+ *      Array of consoles built from command line options (console=)
+ */
+struct console_cmdline
+{
+        char    name[8];                        /* Name of the driver       */
+        int     index;                          /* Minor dev. to use        */
+        char    *options;                       /* Options for the driver   */
+};
+
+#define MAX_CMDLINECONSOLES 8
+
+static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
+static int selected_console = -1;
+static int preferred_console = -1;
+
+/* Flag: console code may call schedule() */
+static int console_may_schedule;
+
+/*
+ *      Setup a list of consoles. Called from init/main.c
+ */
+static int __init console_setup(char *str)
+{
+        char name[sizeof(console_cmdline[0].name)];
+        char *s, *options;
+        int idx;
+
+        /*
+         *      Decode str into name, index, options.
+         */
+        if (str[0] >= '0' && str[0] <= '9') {
+                strcpy(name, "ttyS");
+                strncpy(name + 4, str, sizeof(name) - 5);
+        } else
+                strncpy(name, str, sizeof(name) - 1);
+        name[sizeof(name) - 1] = 0;
+        if ((options = strchr(str, ',')) != NULL)
+                *(options++) = 0;
+#ifdef __sparc__
+        if (!strcmp(str, "ttya"))
+                strcpy(name, "ttyS0");
+        if (!strcmp(str, "ttyb"))
+                strcpy(name, "ttyS1");
+#endif
+        for(s = name; *s; s++)
+                if ((*s >= '0' && *s <= '9') || *s == ',')
+                        break;
+        idx = simple_strtoul(s, NULL, 10);
+        *s = 0;
+
+        add_preferred_console(name, idx, options);
+        return 1;
+}
+
+__setup("console=", console_setup);
+
+/**
+ * add_preferred_console - add a device to the list of preferred consoles.
+ *
+ * The last preferred console added will be used for kernel messages
+ * and stdin/out/err for init.  Normally this is used by console_setup
+ * above to handle user-supplied console arguments; however it can also
+ * be used by arch-specific code either to override the user or more
+ * commonly to provide a default console (ie from PROM variables) when
+ * the user has not supplied one.
+ */
+int __init add_preferred_console(char *name, int idx, char *options)
+{
+        struct console_cmdline *c;
+        int i;
+
+        /*
+         *      See if this tty is not yet registered, and
+         *      if we have a slot free.
+         */
+        for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
+                if (strcmp(console_cmdline[i].name, name) == 0 &&
+                          console_cmdline[i].index == idx) {
+                                selected_console = i;
+                                return 0;
+                }
+        if (i == MAX_CMDLINECONSOLES)
+                return -E2BIG;
+        selected_console = i;
+        c = &console_cmdline[i];
+        memcpy(c->name, name, sizeof(c->name));
+        c->name[sizeof(c->name) - 1] = 0;
+        c->options = options;
+        c->index = idx;
+        return 0;
+}
+
+static int __init log_buf_len_setup(char *str)
+{
+        unsigned long size = memparse(str, &str);
+        unsigned long flags;
+
+        if (size)
+                size = roundup_pow_of_two(size);
+        if (size > log_buf_len) {
+                unsigned long start, dest_idx, offset;
+                char * new_log_buf;
+
+                new_log_buf = alloc_bootmem(size);
+                if (!new_log_buf) {
+                        printk("log_buf_len: allocation failed\n");
+                        goto out;
+                }
+
+                spin_lock_irqsave(&logbuf_lock, flags);
+                log_buf_len = size;
+                log_buf = new_log_buf;
+
+                offset = start = min(con_start, log_start);
+                dest_idx = 0;
+                while (start != log_end) {
+                        log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
+                        start++;
+                        dest_idx++;
+                }
+                log_start -= offset;
+                con_start -= offset;
+                log_end -= offset;
+                spin_unlock_irqrestore(&logbuf_lock, flags);
+
+                printk("log_buf_len: %d\n", log_buf_len);
+        }
+out:
+
+        return 1;
+}
+
+__setup("log_buf_len=", log_buf_len_setup);
+
+/*
+ * Commands to do_syslog:
+ *
+ *      0 -- Close the log.  Currently a NOP.
+ *      1 -- Open the log. Currently a NOP.
+ *      2 -- Read from the log.
+ *      3 -- Read all messages remaining in the ring buffer.
+ *      4 -- Read and clear all messages remaining in the ring buffer
+ *      5 -- Clear ring buffer.
+ *      6 -- Disable printk's to console
+ *      7 -- Enable printk's to console
+ *      8 -- Set level of messages printed to console
+ *      9 -- Return number of unread characters in the log buffer
+ *     10 -- Return size of the log buffer
+ */
+int do_syslog(int type, char __user * buf, int len)
+{
+        unsigned long i, j, limit, count;
+        int do_clear = 0;
+        char c;
+        int error = 0;
+
+        error = security_syslog(type);
+        if (error)
+                return error;
+
+        switch (type) {
+        case 0:         /* Close log */
+                break;
+        case 1:         /* Open log */
+                break;
+        case 2:         /* Read from log */
+                error = -EINVAL;
+                if (!buf || len < 0)
+                        goto out;
+                error = 0;
+                if (!len)
+                        goto out;
+                if (!access_ok(VERIFY_WRITE, buf, len)) {
+                        error = -EFAULT;
+                        goto out;
+                }
+                error = wait_event_interruptible(log_wait, (log_start - log_end));
+                if (error)
+                        goto out;
+                i = 0;
+                spin_lock_irq(&logbuf_lock);
+                while (!error && (log_start != log_end) && i < len) {
+                        c = LOG_BUF(log_start);
+                        log_start++;
+                        spin_unlock_irq(&logbuf_lock);
+                        error = __put_user(c,buf);
+                        buf++;
+                        i++;
+                        cond_resched();
+                        spin_lock_irq(&logbuf_lock);
+                }
+                spin_unlock_irq(&logbuf_lock);
+                if (!error)
+                        error = i;
+                break;
+        case 4:         /* Read/clear last kernel messages */
+                do_clear = 1; 
+                /* FALL THRU */
+        case 3:         /* Read last kernel messages */
+                error = -EINVAL;
+                if (!buf || len < 0)
+                        goto out;
+                error = 0;
+                if (!len)
+                        goto out;
+                if (!access_ok(VERIFY_WRITE, buf, len)) {
+                        error = -EFAULT;
+                        goto out;
+                }
+                count = len;
+                if (count > log_buf_len)
+                        count = log_buf_len;
+                spin_lock_irq(&logbuf_lock);
+                if (count > logged_chars)
+                        count = logged_chars;
+                if (do_clear)
+                        logged_chars = 0;
+                limit = log_end;
+                /*
+                 * __put_user() could sleep, and while we sleep
+                 * printk() could overwrite the messages 
+                 * we try to copy to user space. Therefore
+                 * the messages are copied in reverse. <manfreds>
+                 */
+                for(i = 0; i < count && !error; i++) {
+                        j = limit-1-i;
+                        if (j + log_buf_len < log_end)
+                                break;
+                        c = LOG_BUF(j);
+                        spin_unlock_irq(&logbuf_lock);
+                        error = __put_user(c,&buf[count-1-i]);
+                        cond_resched();
+                        spin_lock_irq(&logbuf_lock);
+                }
+                spin_unlock_irq(&logbuf_lock);
+                if (error)
+                        break;
+                error = i;
+                if(i != count) {
+                        int offset = count-error;
+                        /* buffer overflow during copy, correct user buffer. */
+                        for(i=0;i<error;i++) {
+                                if (__get_user(c,&buf[i+offset]) ||
+                                    __put_user(c,&buf[i])) {
+                                        error = -EFAULT;
+                                        break;
+                                }
+                                cond_resched();
+                        }
+                }
+                break;
+        case 5:         /* Clear ring buffer */
+                logged_chars = 0;
+                break;
+        case 6:         /* Disable logging to console */
+                console_loglevel = minimum_console_loglevel;
+                break;
+        case 7:         /* Enable logging to console */
+                console_loglevel = default_console_loglevel;
+                break;
+        case 8:         /* Set level of messages printed to console */
+                error = -EINVAL;
+                if (len < 1 || len > 8)
+                        goto out;
+                if (len < minimum_console_loglevel)
+                        len = minimum_console_loglevel;
+                console_loglevel = len;
+                error = 0;
+                break;
+        case 9:         /* Number of chars in the log buffer */
+                error = log_end - log_start;
+                break;
+        case 10:        /* Size of the log buffer */
+                error = log_buf_len;
+                break;
+        default:
+                error = -EINVAL;
+                break;
+        }
+out:
+        return error;
+}
+
+asmlinkage long sys_syslog(int type, char __user * buf, int len)
+{
+        return do_syslog(type, buf, len);
+}
+
+/*
+ * Call the console drivers on a range of log_buf
+ */
+static void __call_console_drivers(unsigned long start, unsigned long end)
+{
+        struct console *con;
+
+        for (con = console_drivers; con; con = con->next) {
+                if ((con->flags & CON_ENABLED) && con->write)
+                        con->write(con, &LOG_BUF(start), end - start);
+        }
+}
+
+/*
+ * Write out chars from start to end - 1 inclusive
+ */
+static void _call_console_drivers(unsigned long start,
+                                unsigned long end, int msg_log_level)
+{
+        if (msg_log_level < console_loglevel &&
+                        console_drivers && start != end) {
+                if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
+                        /* wrapped write */
+                        __call_console_drivers(start & LOG_BUF_MASK,
+                                                log_buf_len);
+                        __call_console_drivers(0, end & LOG_BUF_MASK);
+                } else {
+                        __call_console_drivers(start, end);
+                }
+        }
+}
+
+/*
+ * Call the console drivers, asking them to write out
+ * log_buf[start] to log_buf[end - 1].
+ * The console_sem must be held.
+ */
+static void call_console_drivers(unsigned long start, unsigned long end)
+{
+        unsigned long cur_index, start_print;
+        static int msg_level = -1;
+
+        if (((long)(start - end)) > 0)
+                BUG();
+
+        cur_index = start;
+        start_print = start;
+        while (cur_index != end) {
+                if (    msg_level < 0 &&
+                        ((end - cur_index) > 2) &&
+                        LOG_BUF(cur_index + 0) == '<' &&
+                        LOG_BUF(cur_index + 1) >= '0' &&
+                        LOG_BUF(cur_index + 1) <= '7' &&
+                        LOG_BUF(cur_index + 2) == '>')
+                {
+                        msg_level = LOG_BUF(cur_index + 1) - '0';
+                        cur_index += 3;
+                        start_print = cur_index;
+                }
+                while (cur_index != end) {
+                        char c = LOG_BUF(cur_index);
+                        cur_index++;
+
+                        if (c == '\n') {
+                                if (msg_level < 0) {
+                                        /*
+                                         * printk() has already given us loglevel tags in
+                                         * the buffer.  This code is here in case the
+                                         * log buffer has wrapped right round and scribbled
+                                         * on those tags
+                                         */
+                                        msg_level = default_message_loglevel;
+                                }
+                                _call_console_drivers(start_print, cur_index, msg_level);
+                                msg_level = -1;
+                                start_print = cur_index;
+                                break;
+                        }
+                }
+        }
+        _call_console_drivers(start_print, end, msg_level);
+}
+
+static void emit_log_char(char c)
+{
+        LOG_BUF(log_end) = c;
+        log_end++;
+        if (log_end - log_start > log_buf_len)
+                log_start = log_end - log_buf_len;
+        if (log_end - con_start > log_buf_len)
+                con_start = log_end - log_buf_len;
+        if (logged_chars < log_buf_len)
+                logged_chars++;
+}
+
+/*
+ * Zap console related locks when oopsing. Only zap at most once
+ * every 10 seconds, to leave time for slow consoles to print a
+ * full oops.
+ */
+static void zap_locks(void)
+{
+        static unsigned long oops_timestamp;
+
+        if (time_after_eq(jiffies, oops_timestamp) &&
+                        !time_after(jiffies, oops_timestamp + 30*HZ))
+                return;
+
+        oops_timestamp = jiffies;
+
+        /* If a crash is occurring, make sure we can't deadlock */
+        spin_lock_init(&logbuf_lock);
+        /* And make sure that we print immediately */
+        init_MUTEX(&console_sem);
+}
+
+#if defined(CONFIG_PRINTK_TIME)
+static int printk_time = 1;
+#else
+static int printk_time = 0;
+#endif
+
+static int __init printk_time_setup(char *str)
+{
+        if (*str)
+                return 0;
+        printk_time = 1;
+        return 1;
+}
+
+__setup("time", printk_time_setup);
+
+/*
+ * This is printk.  It can be called from any context.  We want it to work.
+ * 
+ * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
+ * call the console drivers.  If we fail to get the semaphore we place the output
+ * into the log buffer and return.  The current holder of the console_sem will
+ * notice the new output in release_console_sem() and will send it to the
+ * consoles before releasing the semaphore.
+ *
+ * One effect of this deferred printing is that code which calls printk() and
+ * then changes console_loglevel may break. This is because console_loglevel
+ * is inspected when the actual printing occurs.
+ */
+asmlinkage int printk(const char *fmt, ...)
+{
+        va_list args;
+        int r;
+
+        va_start(args, fmt);
+        r = vprintk(fmt, args);
+        va_end(args);
+
+        return r;
+}
+
+asmlinkage int vprintk(const char *fmt, va_list args)
+{
+        unsigned long flags;
+        int printed_len;
+        char *p;
+        static char printk_buf[1024];
+        static int log_level_unknown = 1;
+
+        if (unlikely(oops_in_progress))
+                zap_locks();
+
+        /* This stops the holder of console_sem just where we want him */
+        spin_lock_irqsave(&logbuf_lock, flags);
+
+        /* Emit the output into the temporary buffer */
+        printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
+
+        /*
+         * Copy the output into log_buf.  If the caller didn't provide
+         * appropriate log level tags, we insert them here
+         */
+        for (p = printk_buf; *p; p++) {
+                if (log_level_unknown) {
+                        /* log_level_unknown signals the start of a new line */
+                        if (printk_time) {
+                                int loglev_char;
+                                char tbuf[50], *tp;
+                                unsigned tlen;
+                                unsigned long long t;
+                                unsigned long nanosec_rem;
+
+                                /*
+                                 * force the log level token to be
+                                 * before the time output.
+                                 */
+                                if (p[0] == '<' && p[1] >='0' &&
+                                   p[1] <= '7' && p[2] == '>') {
+                                        loglev_char = p[1];
+                                        p += 3;
+                                        printed_len += 3;
+                                } else {
+                                        loglev_char = default_message_loglevel
+                                                + '0';
+                                }
+                                t = sched_clock();
+                                nanosec_rem = do_div(t, 1000000000);
+                                tlen = sprintf(tbuf,
+                                                "<%c>[%5lu.%06lu] ",
+                                                loglev_char,
+                                                (unsigned long)t,
+                                                nanosec_rem/1000);
+
+                                for (tp = tbuf; tp < tbuf + tlen; tp++)
+                                        emit_log_char(*tp);
+                                printed_len += tlen - 3;
+                        } else {
+                                if (p[0] != '<' || p[1] < '0' ||
+                                   p[1] > '7' || p[2] != '>') {
+                                        emit_log_char('<');
+                                        emit_log_char(default_message_loglevel
+                                                + '0');
+                                        emit_log_char('>');
+                                }
+                                printed_len += 3;
+                        }
+                        log_level_unknown = 0;
+                        if (!*p)
+                                break;
+                }
+                emit_log_char(*p);
+                if (*p == '\n')
+                        log_level_unknown = 1;
+        }
+
+        if (!cpu_online(smp_processor_id()) &&
+            system_state != SYSTEM_RUNNING) {
+                /*
+                 * Some console drivers may assume that per-cpu resources have
+                 * been allocated.  So don't allow them to be called by this
+                 * CPU until it is officially up.  We shouldn't be calling into
+                 * random console drivers on a CPU which doesn't exist yet..
+                 */
+                spin_unlock_irqrestore(&logbuf_lock, flags);
+                goto out;
+        }
+        if (!down_trylock(&console_sem)) {
+                console_locked = 1;
+                /*
+                 * We own the drivers.  We can drop the spinlock and let
+                 * release_console_sem() print the text
+                 */
+                spin_unlock_irqrestore(&logbuf_lock, flags);
+                console_may_schedule = 0;
+                release_console_sem();
+        } else {
+                /*
+                 * Someone else owns the drivers.  We drop the spinlock, which
+                 * allows the semaphore holder to proceed and to call the
+                 * console drivers with the output which we just produced.
+                 */
+                spin_unlock_irqrestore(&logbuf_lock, flags);
+        }
+out:
+        return printed_len;
+}
+EXPORT_SYMBOL(printk);
+EXPORT_SYMBOL(vprintk);
+
+/**
+ * acquire_console_sem - lock the console system for exclusive use.
+ *
+ * Acquires a semaphore which guarantees that the caller has
+ * exclusive access to the console system and the console_drivers list.
+ *
+ * Can sleep, returns nothing.
+ */
+void acquire_console_sem(void)
+{
+        if (in_interrupt())
+                BUG();
+        down(&console_sem);
+        console_locked = 1;
+        console_may_schedule = 1;
+}
+EXPORT_SYMBOL(acquire_console_sem);
+
+int try_acquire_console_sem(void)
+{
+        if (down_trylock(&console_sem))
+                return -1;
+        console_locked = 1;
+        console_may_schedule = 0;
+        return 0;
+}
+EXPORT_SYMBOL(try_acquire_console_sem);
+
+int is_console_locked(void)
+{
+        return console_locked;
+}
+EXPORT_SYMBOL(is_console_locked);
+
+/**
+ * release_console_sem - unlock the console system
+ *
+ * Releases the semaphore which the caller holds on the console system
+ * and the console driver list.
+ *
+ * While the semaphore was held, console output may have been buffered
+ * by printk().  If this is the case, release_console_sem() emits
+ * the output prior to releasing the semaphore.
+ *
+ * If there is output waiting for klogd, we wake it up.
+ *
+ * release_console_sem() may be called from any context.
+ */
+void release_console_sem(void)
+{
+        unsigned long flags;
+        unsigned long _con_start, _log_end;
+        unsigned long wake_klogd = 0;
+
+        for ( ; ; ) {
+                spin_lock_irqsave(&logbuf_lock, flags);
+                wake_klogd |= log_start - log_end;
+                if (con_start == log_end)
+                        break;                  /* Nothing to print */
+                _con_start = con_start;
+                _log_end = log_end;
+                con_start = log_end;            /* Flush */
+                spin_unlock(&logbuf_lock);
+                call_console_drivers(_con_start, _log_end);
+                local_irq_restore(flags);
+        }
+        console_locked = 0;
+        console_may_schedule = 0;
+        up(&console_sem);
+        spin_unlock_irqrestore(&logbuf_lock, flags);
+        if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
+                wake_up_interruptible(&log_wait);
+}
+EXPORT_SYMBOL(release_console_sem);
+
+/** console_conditional_schedule - yield the CPU if required
+ *
+ * If the console code is currently allowed to sleep, and
+ * if this CPU should yield the CPU to another task, do
+ * so here.
+ *
+ * Must be called within acquire_console_sem().
+ */
+void __sched console_conditional_schedule(void)
+{
+        if (console_may_schedule)
+                cond_resched();
+}
+EXPORT_SYMBOL(console_conditional_schedule);
+
+void console_print(const char *s)
+{
+        printk(KERN_EMERG "%s", s);
+}
+EXPORT_SYMBOL(console_print);
+
+void console_unblank(void)
+{
+        struct console *c;
+
+        /*
+         * console_unblank can no longer be called in interrupt context unless
+         * oops_in_progress is set to 1..
+         */
+        if (oops_in_progress) {
+                if (down_trylock(&console_sem) != 0)
+                        return;
+        } else
+                acquire_console_sem();
+
+        console_locked = 1;
+        console_may_schedule = 0;
+        for (c = console_drivers; c != NULL; c = c->next)
+                if ((c->flags & CON_ENABLED) && c->unblank)
+                        c->unblank();
+        release_console_sem();
+}
+EXPORT_SYMBOL(console_unblank);
+
+/*
+ * Return the console tty driver structure and its associated index
+ */
+struct tty_driver *console_device(int *index)
+{
+        struct console *c;
+        struct tty_driver *driver = NULL;
+
+        acquire_console_sem();
+        for (c = console_drivers; c != NULL; c = c->next) {
+                if (!c->device)
+                        continue;
+                driver = c->device(c, index);
+                if (driver)
+                        break;
+        }
+        release_console_sem();
+        return driver;
+}
+
+/*
+ * Prevent further output on the passed console device so that (for example)
+ * serial drivers can disable console output before suspending a port, and can
+ * re-enable output afterwards.
+ */
+void console_stop(struct console *console)
+{
+        acquire_console_sem();
+        console->flags &= ~CON_ENABLED;
+        release_console_sem();
+}
+EXPORT_SYMBOL(console_stop);
+
+void console_start(struct console *console)
+{
+        acquire_console_sem();
+        console->flags |= CON_ENABLED;
+        release_console_sem();
+}
+EXPORT_SYMBOL(console_start);
+
+/*
+ * The console driver calls this routine during kernel initialization
+ * to register the console printing procedure with printk() and to
+ * print any messages that were printed by the kernel before the
+ * console driver was initialized.
+ */
+void register_console(struct console * console)
+{
+        int     i;
+        unsigned long flags;
+
+        if (preferred_console < 0)
+                preferred_console = selected_console;
+
+        /*
+         *      See if we want to use this console driver. If we
+         *      didn't select a console we take the first one
+         *      that registers here.
+         */
+        if (preferred_console < 0) {
+                if (console->index < 0)
+                        console->index = 0;
+                if (console->setup == NULL ||
+                    console->setup(console, NULL) == 0) {
+                        console->flags |= CON_ENABLED | CON_CONSDEV;
+                        preferred_console = 0;
+                }
+        }
+
+        /*
+         *      See if this console matches one we selected on
+         *      the command line.
+         */
+        for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) {
+                if (strcmp(console_cmdline[i].name, console->name) != 0)
+                        continue;
+                if (console->index >= 0 &&
+                    console->index != console_cmdline[i].index)
+                        continue;
+                if (console->index < 0)
+                        console->index = console_cmdline[i].index;
+                if (console->setup &&
+                    console->setup(console, console_cmdline[i].options) != 0)
+                        break;
+                console->flags |= CON_ENABLED;
+                console->index = console_cmdline[i].index;
+                if (i == preferred_console)
+                        console->flags |= CON_CONSDEV;
+                break;
+        }
+
+        if (!(console->flags & CON_ENABLED))
+                return;
+
+        if (console_drivers && (console_drivers->flags & CON_BOOT)) {
+                unregister_console(console_drivers);
+                console->flags &= ~CON_PRINTBUFFER;
+        }
+
+        /*
+         *      Put this console in the list - keep the
+         *      preferred driver at the head of the list.
+         */
+        acquire_console_sem();
+        if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
+                console->next = console_drivers;
+                console_drivers = console;
+        } else {
+                console->next = console_drivers->next;
+                console_drivers->next = console;
+        }
+        if (console->flags & CON_PRINTBUFFER) {
+                /*
+                 * release_console_sem() will print out the buffered messages
+                 * for us.
+                 */
+                spin_lock_irqsave(&logbuf_lock, flags);
+                con_start = log_start;
+                spin_unlock_irqrestore(&logbuf_lock, flags);
+        }
+        release_console_sem();
+}
+EXPORT_SYMBOL(register_console);
+
+int unregister_console(struct console * console)
+{
+        struct console *a,*b;
+        int res = 1;
+
+        acquire_console_sem();
+        if (console_drivers == console) {
+                console_drivers=console->next;
+                res = 0;
+        } else {
+                for (a=console_drivers->next, b=console_drivers ;
+                     a; b=a, a=b->next) {
+                        if (a == console) {
+                                b->next = a->next;
+                                res = 0;
+                                break;
+                        }  
+                }
+        }
+        
+        /* If last console is removed, we re-enable picking the first
+         * one that gets registered. Without that, pmac early boot console
+         * would prevent fbcon from taking over.
+         */
+        if (console_drivers == NULL)
+                preferred_console = selected_console;
+                
+
+        release_console_sem();
+        return res;
+}
+EXPORT_SYMBOL(unregister_console);
+        
+/**
+ * tty_write_message - write a message to a certain tty, not just the console.
+ *
+ * This is used for messages that need to be redirected to a specific tty.
+ * We don't put it into the syslog queue right now maybe in the future if
+ * really needed.
+ */
+void tty_write_message(struct tty_struct *tty, char *msg)
+{
+        if (tty && tty->driver->write)
+                tty->driver->write(tty, msg, strlen(msg));
+        return;
+}
+
+/*
+ * printk rate limiting, lifted from the networking subsystem.
+ *
+ * This enforces a rate limit: not more than one kernel message
+ * every printk_ratelimit_jiffies to make a denial-of-service
+ * attack impossible.
+ */
+int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
+{
+        static DEFINE_SPINLOCK(ratelimit_lock);
+        static unsigned long toks = 10*5*HZ;
+        static unsigned long last_msg;
+        static int missed;
+        unsigned long flags;
+        unsigned long now = jiffies;
+
+        spin_lock_irqsave(&ratelimit_lock, flags);
+        toks += now - last_msg;
+        last_msg = now;
+        if (toks > (ratelimit_burst * ratelimit_jiffies))
+                toks = ratelimit_burst * ratelimit_jiffies;
+        if (toks >= ratelimit_jiffies) {
+                int lost = missed;
+                missed = 0;
+                toks -= ratelimit_jiffies;
+                spin_unlock_irqrestore(&ratelimit_lock, flags);
+                if (lost)
+                        printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
+                return 1;
+        }
+        missed++;
+        spin_unlock_irqrestore(&ratelimit_lock, flags);
+        return 0;
+}
+EXPORT_SYMBOL(__printk_ratelimit);
+
+/* minimum time in jiffies between messages */
+int printk_ratelimit_jiffies = 5*HZ;
+
+/* number of messages we send before ratelimiting */
+int printk_ratelimit_burst = 10;
+
+int printk_ratelimit(void)
+{
+        return __printk_ratelimit(printk_ratelimit_jiffies,
+                                printk_ratelimit_burst);
+}
+EXPORT_SYMBOL(printk_ratelimit);