Merge 'Linux v3.0' into Litmus

Some notes:
* Litmus^RT scheduling class is the topmost scheduling class
  (above stop_sched_class).
* scheduler_ipi() function (e.g., in smp_reschedule_interrupt())
  may increase IPI latencies.
* Added path into schedule() to quickly re-evaluate scheduling
  decision without becoming preemptive again. This used to be
  a standard path before the removal of BKL.

Conflicts:
	Makefile
	arch/arm/kernel/calls.S
	arch/arm/kernel/smp.c
	arch/x86/include/asm/unistd_32.h
	arch/x86/kernel/smp.c
	arch/x86/kernel/syscall_table_32.S
	include/linux/hrtimer.h
	kernel/printk.c
	kernel/sched.c
	kernel/sched_fair.c

1 files changed, 312 insertions, 149 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 9dc8ea140426..b799a2ee96e5 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -31,6 +31,7 @@
 #include <linux/smp.h>
 #include <linux/security.h>
 #include <linux/bootmem.h>
+#include <linux/memblock.h>
 #include <linux/syscalls.h>
 #include <linux/kexec.h>
 #include <linux/kdb.h>
@@ -39,16 +40,11 @@
 #include <linux/syslog.h>
 #include <linux/cpu.h>
 #include <linux/notifier.h>
+#include <linux/rculist.h>
 
 #include <asm/uaccess.h>
 
 /*
- * for_each_console() allows you to iterate on each console
- */
-#define for_each_console(con) \
-        for (con = console_drivers; con != NULL; con = con->next)
-
-/*
  * Architectures can override it:
  */
 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
@@ -58,7 +54,7 @@ void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
 
 /* printk's without a loglevel use this.. */
-#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
+#define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
 
 /* We show everything that is MORE important than this.. */
 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
@@ -92,7 +88,7 @@ EXPORT_SYMBOL(oops_in_progress);
  * provides serialisation for access to the entire console
  * driver system.
  */
-static DECLARE_MUTEX(console_sem);
+static DEFINE_SEMAPHORE(console_sem);
 struct console *console_drivers;
 EXPORT_SYMBOL_GPL(console_drivers);
 
@@ -109,7 +105,7 @@ static int console_locked, console_suspended;
 /*
  * 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().
+ * console_unlock();.
  */
 static DEFINE_SPINLOCK(logbuf_lock);
 
@@ -125,6 +121,11 @@ static unsigned con_start;	/* Index into log_buf: next char to be sent to consol
 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 
 /*
+ * If exclusive_console is non-NULL then only this console is to be printed to.
+ */
+static struct console *exclusive_console;
+
+/*
  *      Array of consoles built from command line options (console=)
  */
 struct console_cmdline
@@ -174,50 +175,78 @@ void log_buf_kexec_setup(void)
 }
 #endif
 
+/* requested log_buf_len from kernel cmdline */
+static unsigned long __initdata new_log_buf_len;
+
+/* save requested log_buf_len since it's too early to process it */
 static int __init log_buf_len_setup(char *str)
 {
         unsigned size = memparse(str, &str);
-        unsigned long flags;
 
         if (size)
                 size = roundup_pow_of_two(size);
-        if (size > log_buf_len) {
-                unsigned start, dest_idx, offset;
-                char *new_log_buf;
+        if (size > log_buf_len)
+                new_log_buf_len = size;
 
-                new_log_buf = alloc_bootmem(size);
-                if (!new_log_buf) {
-                        printk(KERN_WARNING "log_buf_len: allocation failed\n");
-                        goto out;
-                }
+        return 0;
+}
+early_param("log_buf_len", log_buf_len_setup);
 
-                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);
+void __init setup_log_buf(int early)
+{
+        unsigned long flags;
+        unsigned start, dest_idx, offset;
+        char *new_log_buf;
+        int free;
+
+        if (!new_log_buf_len)
+                return;
+
+        if (early) {
+                unsigned long mem;
 
-                printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
+                mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
+                if (mem == MEMBLOCK_ERROR)
+                        return;
+                new_log_buf = __va(mem);
+        } else {
+                new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
         }
-out:
-        return 1;
-}
 
-__setup("log_buf_len=", log_buf_len_setup);
+        if (unlikely(!new_log_buf)) {
+                pr_err("log_buf_len: %ld bytes not available\n",
+                        new_log_buf_len);
+                return;
+        }
+
+        spin_lock_irqsave(&logbuf_lock, flags);
+        log_buf_len = new_log_buf_len;
+        log_buf = new_log_buf;
+        new_log_buf_len = 0;
+        free = __LOG_BUF_LEN - log_end;
+
+        offset = start = min(con_start, log_start);
+        dest_idx = 0;
+        while (start != log_end) {
+                unsigned log_idx_mask = start & (__LOG_BUF_LEN - 1);
+
+                log_buf[dest_idx] = __log_buf[log_idx_mask];
+                start++;
+                dest_idx++;
+        }
+        log_start -= offset;
+        con_start -= offset;
+        log_end -= offset;
+        spin_unlock_irqrestore(&logbuf_lock, flags);
+
+        pr_info("log_buf_len: %d\n", log_buf_len);
+        pr_info("early log buf free: %d(%d%%)\n",
+                free, (free * 100) / __LOG_BUF_LEN);
+}
 
 #ifdef CONFIG_BOOT_PRINTK_DELAY
 
-static unsigned int boot_delay; /* msecs delay after each printk during bootup */
+static int boot_delay; /* msecs delay after each printk during bootup */
 static unsigned long long loops_per_msec;       /* based on boot_delay */
 
 static int __init boot_delay_setup(char *str)
@@ -268,14 +297,55 @@ static inline void boot_delay_msec(void)
 }
 #endif
 
+#ifdef CONFIG_SECURITY_DMESG_RESTRICT
+int dmesg_restrict = 1;
+#else
+int dmesg_restrict;
+#endif
+
+static int syslog_action_restricted(int type)
+{
+        if (dmesg_restrict)
+                return 1;
+        /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
+        return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
+}
+
+static int check_syslog_permissions(int type, bool from_file)
+{
+        /*
+         * If this is from /proc/kmsg and we've already opened it, then we've
+         * already done the capabilities checks at open time.
+         */
+        if (from_file && type != SYSLOG_ACTION_OPEN)
+                return 0;
+
+        if (syslog_action_restricted(type)) {
+                if (capable(CAP_SYSLOG))
+                        return 0;
+                /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
+                if (capable(CAP_SYS_ADMIN)) {
+                        WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
+                                 "but no CAP_SYSLOG (deprecated).\n");
+                        return 0;
+                }
+                return -EPERM;
+        }
+        return 0;
+}
+
 int do_syslog(int type, char __user *buf, int len, bool from_file)
 {
         unsigned i, j, limit, count;
         int do_clear = 0;
         char c;
-        int error = 0;
+        int error;
+
+        error = check_syslog_permissions(type, from_file);
+        if (error)
+                goto out;
 
-        error = security_syslog(type, from_file);
+        error = security_syslog(type);
         if (error)
                 return error;
 
@@ -447,6 +517,8 @@ static void __call_console_drivers(unsigned start, unsigned end)
         struct console *con;
 
         for_each_console(con) {
+                if (exclusive_console && con != exclusive_console)
+                        continue;
                 if ((con->flags & CON_ENABLED) && con->write &&
                                 (cpu_online(smp_processor_id()) ||
                                 (con->flags & CON_ANYTIME)))
@@ -486,9 +558,74 @@ static void _call_console_drivers(unsigned start,
 }
 
 /*
+ * Parse the syslog header <[0-9]*>. The decimal value represents 32bit, the
+ * lower 3 bit are the log level, the rest are the log facility. In case
+ * userspace passes usual userspace syslog messages to /dev/kmsg or
+ * /dev/ttyprintk, the log prefix might contain the facility. Printk needs
+ * to extract the correct log level for in-kernel processing, and not mangle
+ * the original value.
+ *
+ * If a prefix is found, the length of the prefix is returned. If 'level' is
+ * passed, it will be filled in with the log level without a possible facility
+ * value. If 'special' is passed, the special printk prefix chars are accepted
+ * and returned. If no valid header is found, 0 is returned and the passed
+ * variables are not touched.
+ */
+static size_t log_prefix(const char *p, unsigned int *level, char *special)
+{
+        unsigned int lev = 0;
+        char sp = '\0';
+        size_t len;
+
+        if (p[0] != '<' || !p[1])
+                return 0;
+        if (p[2] == '>') {
+                /* usual single digit level number or special char */
+                switch (p[1]) {
+                case '0' ... '7':
+                        lev = p[1] - '0';
+                        break;
+                case 'c': /* KERN_CONT */
+                case 'd': /* KERN_DEFAULT */
+                        sp = p[1];
+                        break;
+                default:
+                        return 0;
+                }
+                len = 3;
+        } else {
+                /* multi digit including the level and facility number */
+                char *endp = NULL;
+
+                if (p[1] < '0' && p[1] > '9')
+                        return 0;
+
+                lev = (simple_strtoul(&p[1], &endp, 10) & 7);
+                if (endp == NULL || endp[0] != '>')
+                        return 0;
+                len = (endp + 1) - p;
+        }
+
+        /* do not accept special char if not asked for */
+        if (sp && !special)
+                return 0;
+
+        if (special) {
+                *special = sp;
+                /* return special char, do not touch level */
+                if (sp)
+                        return len;
+        }
+
+        if (level)
+                *level = lev;
+        return len;
+}
+
+/*
  * Call the console drivers, asking them to write out
  * log_buf[start] to log_buf[end - 1].
- * The console_sem must be held.
+ * The console_lock must be held.
  */
 static void call_console_drivers(unsigned start, unsigned end)
 {
@@ -500,13 +637,9 @@ static void call_console_drivers(unsigned start, unsigned end)
         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;
+                if (msg_level < 0 && ((end - cur_index) > 2)) {
+                        /* strip log prefix */
+                        cur_index += log_prefix(&LOG_BUF(cur_index), &msg_level, NULL);
                         start_print = cur_index;
                 }
                 while (cur_index != end) {
@@ -563,7 +696,7 @@ static void zap_locks(void)
         /* 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);
+        sema_init(&console_sem, 1);
 }
 
 #if defined(CONFIG_PRINTK_TIME)
@@ -591,11 +724,11 @@ static int have_callable_console(void)
  *
  * 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
+ * We try to grab the console_lock.  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.
+ * notice the new output in console_unlock(); and will send it to the
+ * consoles before releasing the lock.
  *
  * One effect of this deferred printing is that code which calls printk() and
  * then changes console_loglevel may break. This is because console_loglevel
@@ -646,18 +779,19 @@ static inline int can_use_console(unsigned int cpu)
 /*
  * Try to get console ownership to actually show the kernel
  * messages from a 'printk'. Return true (and with the
- * console_semaphore held, and 'console_locked' set) if it
+ * console_lock held, and 'console_locked' set) if it
  * is successful, false otherwise.
  *
  * This gets called with the 'logbuf_lock' spinlock held and
  * interrupts disabled. It should return with 'lockbuf_lock'
  * released but interrupts still disabled.
  */
-static int acquire_console_semaphore_for_printk(unsigned int cpu)
+static int console_trylock_for_printk(unsigned int cpu)
+        __releases(&logbuf_lock)
 {
         int retval = 0;
 
-        if (!try_acquire_console_sem()) {
+        if (console_trylock()) {
                 retval = 1;
 
                 /*
@@ -703,6 +837,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
         unsigned long flags;
         int this_cpu;
         char *p;
+        size_t plen;
+        char special;
 
         boot_delay_msec();
         printk_delay();
@@ -746,45 +882,52 @@ asmlinkage int vprintk(const char *fmt, va_list args)
         if (trace_override && !trace_recurse)
                 TRACE("%s", printk_buf);
 
-
         p = printk_buf;
 
-        /* Do we have a loglevel in the string? */
-        if (p[0] == '<') {
-                unsigned char c = p[1];
-                if (c && p[2] == '>') {
-                        switch (c) {
-                        case '0' ... '7': /* loglevel */
-                                current_log_level = c - '0';
-                        /* Fallthrough - make sure we're on a new line */
-                        case 'd': /* KERN_DEFAULT */
-                                if (!new_text_line) {
-                                        emit_log_char('\n');
-                                        new_text_line = 1;
-                                }
-                        /* Fallthrough - skip the loglevel */
-                        case 'c': /* KERN_CONT */
-                                p += 3;
-                                break;
+        /* Read log level and handle special printk prefix */
+        plen = log_prefix(p, &current_log_level, &special);
+        if (plen) {
+                p += plen;
+
+                switch (special) {
+                case 'c': /* Strip <c> KERN_CONT, continue line */
+                        plen = 0;
+                        break;
+                case 'd': /* Strip <d> KERN_DEFAULT, start new line */
+                        plen = 0;
+                default:
+                        if (!new_text_line) {
+                                emit_log_char('\n');
+                                new_text_line = 1;
                         }
                 }
         }
 
         /*
-         * Copy the output into log_buf.  If the caller didn't provide
-         * appropriate log level tags, we insert them here
+         * Copy the output into log_buf. If the caller didn't provide
+         * the appropriate log prefix, we insert them here
          */
-        for ( ; *p; p++) {
+        for (; *p; p++) {
                 if (new_text_line) {
-                        /* Always output the token */
-                        emit_log_char('<');
-                        emit_log_char(current_log_level + '0');
-                        emit_log_char('>');
-                        printed_len += 3;
                         new_text_line = 0;
 
+                        if (plen) {
+                                /* Copy original log prefix */
+                                int i;
+
+                                for (i = 0; i < plen; i++)
+                                        emit_log_char(printk_buf[i]);
+                                printed_len += plen;
+                        } else {
+                                /* Add log prefix */
+                                emit_log_char('<');
+                                emit_log_char(current_log_level + '0');
+                                emit_log_char('>');
+                                printed_len += 3;
+                        }
+
                         if (printk_time) {
-                                /* Follow the token with the time */
+                                /* Add the current time stamp */
                                 char tbuf[50], *tp;
                                 unsigned tlen;
                                 unsigned long long t;
@@ -816,12 +959,12 @@ asmlinkage int vprintk(const char *fmt, va_list args)
          * actual magic (print out buffers, wake up klogd,
          * etc).
          *
-         * The acquire_console_semaphore_for_printk() function
+         * The console_trylock_for_printk() function
          * will release 'logbuf_lock' regardless of whether it
          * actually gets the semaphore or not.
          */
-        if (acquire_console_semaphore_for_printk(this_cpu))
-                release_console_sem();
+        if (console_trylock_for_printk(this_cpu))
+                console_unlock();
 
         lockdep_on();
 out_restore_irqs:
@@ -982,7 +1125,7 @@ void suspend_console(void)
         if (!console_suspend_enabled)
                 return;
         printk("Suspending console(s) (use no_console_suspend to debug)\n");
-        acquire_console_sem();
+        console_lock();
         console_suspended = 1;
         up(&console_sem);
 }
@@ -993,7 +1136,7 @@ void resume_console(void)
                 return;
         down(&console_sem);
         console_suspended = 0;
-        release_console_sem();
+        console_unlock();
 }
 
 /**
@@ -1016,21 +1159,21 @@ static int __cpuinit console_cpu_notify(struct notifier_block *self,
         case CPU_DYING:
         case CPU_DOWN_FAILED:
         case CPU_UP_CANCELED:
-                acquire_console_sem();
-                release_console_sem();
+                console_lock();
+                console_unlock();
         }
         return NOTIFY_OK;
 }
 
 /**
- * acquire_console_sem - lock the console system for exclusive use.
+ * console_lock - lock the console system for exclusive use.
  *
- * Acquires a semaphore which guarantees that the caller has
+ * Acquires a lock 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)
+void console_lock(void)
 {
         BUG_ON(in_interrupt());
         down(&console_sem);
@@ -1039,21 +1182,29 @@ void acquire_console_sem(void)
         console_locked = 1;
         console_may_schedule = 1;
 }
-EXPORT_SYMBOL(acquire_console_sem);
+EXPORT_SYMBOL(console_lock);
 
-int try_acquire_console_sem(void)
+/**
+ * console_trylock - try to lock the console system for exclusive use.
+ *
+ * Tried to acquire a lock which guarantees that the caller has
+ * exclusive access to the console system and the console_drivers list.
+ *
+ * returns 1 on success, and 0 on failure to acquire the lock.
+ */
+int console_trylock(void)
 {
         if (down_trylock(&console_sem))
-                return -1;
+                return 0;
         if (console_suspended) {
                 up(&console_sem);
-                return -1;
+                return 0;
         }
         console_locked = 1;
         console_may_schedule = 0;
-        return 0;
+        return 1;
 }
-EXPORT_SYMBOL(try_acquire_console_sem);
+EXPORT_SYMBOL(console_trylock);
 
 int is_console_locked(void)
 {
@@ -1064,38 +1215,40 @@ static DEFINE_PER_CPU(int, printk_pending);
 
 void printk_tick(void)
 {
-        if (__get_cpu_var(printk_pending)) {
-                __get_cpu_var(printk_pending) = 0;
+        if (__this_cpu_read(printk_pending)) {
+                __this_cpu_write(printk_pending, 0);
                 wake_up_interruptible(&log_wait);
         }
 }
 
 int printk_needs_cpu(int cpu)
 {
-        return per_cpu(printk_pending, cpu);
+        if (cpu_is_offline(cpu))
+                printk_tick();
+        return __this_cpu_read(printk_pending);
 }
 
 void wake_up_klogd(void)
 {
         if (!trace_override && waitqueue_active(&log_wait))
-                __raw_get_cpu_var(printk_pending) = 1;
+                this_cpu_write(printk_pending, 1);
 }
 
 /**
- * release_console_sem - unlock the console system
+ * console_unlock - unlock the console system
  *
- * Releases the semaphore which the caller holds on the console system
+ * Releases the console_lock 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.
+ * While the console_lock was held, console output may have been buffered
+ * by printk().  If this is the case, console_unlock(); emits
+ * the output prior to releasing the lock.
  *
  * If there is output waiting for klogd, we wake it up.
  *
- * release_console_sem() may be called from any context.
+ * console_unlock(); may be called from any context.
  */
-void release_console_sem(void)
+void console_unlock(void)
 {
         unsigned long flags;
         unsigned _con_start, _log_end;
@@ -1123,12 +1276,17 @@ void release_console_sem(void)
                 local_irq_restore(flags);
         }
         console_locked = 0;
+
+        /* Release the exclusive_console once it is used */
+        if (unlikely(exclusive_console))
+                exclusive_console = NULL;
+
         up(&console_sem);
         spin_unlock_irqrestore(&logbuf_lock, flags);
         if (wake_klogd)
                 wake_up_klogd();
 }
-EXPORT_SYMBOL(release_console_sem);
+EXPORT_SYMBOL(console_unlock);
 
 /**
  * console_conditional_schedule - yield the CPU if required
@@ -1137,7 +1295,7 @@ EXPORT_SYMBOL(release_console_sem);
  * if this CPU should yield the CPU to another task, do
  * so here.
  *
- * Must be called within acquire_console_sem().
+ * Must be called within console_lock();.
  */
 void __sched console_conditional_schedule(void)
 {
@@ -1158,14 +1316,14 @@ void console_unblank(void)
                 if (down_trylock(&console_sem) != 0)
                         return;
         } else
-                acquire_console_sem();
+                console_lock();
 
         console_locked = 1;
         console_may_schedule = 0;
         for_each_console(c)
                 if ((c->flags & CON_ENABLED) && c->unblank)
                         c->unblank();
-        release_console_sem();
+        console_unlock();
 }
 
 /*
@@ -1176,7 +1334,7 @@ struct tty_driver *console_device(int *index)
         struct console *c;
         struct tty_driver *driver = NULL;
 
-        acquire_console_sem();
+        console_lock();
         for_each_console(c) {
                 if (!c->device)
                         continue;
@@ -1184,7 +1342,7 @@ struct tty_driver *console_device(int *index)
                 if (driver)
                         break;
         }
-        release_console_sem();
+        console_unlock();
         return driver;
 }
 
@@ -1195,20 +1353,32 @@ struct tty_driver *console_device(int *index)
  */
 void console_stop(struct console *console)
 {
-        acquire_console_sem();
+        console_lock();
         console->flags &= ~CON_ENABLED;
-        release_console_sem();
+        console_unlock();
 }
 EXPORT_SYMBOL(console_stop);
 
 void console_start(struct console *console)
 {
-        acquire_console_sem();
+        console_lock();
         console->flags |= CON_ENABLED;
-        release_console_sem();
+        console_unlock();
 }
 EXPORT_SYMBOL(console_start);
 
+static int __read_mostly keep_bootcon;
+
+static int __init keep_bootcon_setup(char *str)
+{
+        keep_bootcon = 1;
+        printk(KERN_INFO "debug: skip boot console de-registration.\n");
+
+        return 0;
+}
+
+early_param("keep_bootcon", keep_bootcon_setup);
+
 /*
  * The console driver calls this routine during kernel initialization
  * to register the console printing procedure with printk() and to
@@ -1327,7 +1497,7 @@ void register_console(struct console *newcon)
          *      Put this console in the list - keep the
          *      preferred driver at the head of the list.
          */
-        acquire_console_sem();
+        console_lock();
         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
                 newcon->next = console_drivers;
                 console_drivers = newcon;
@@ -1339,14 +1509,21 @@ void register_console(struct console *newcon)
         }
         if (newcon->flags & CON_PRINTBUFFER) {
                 /*
-                 * release_console_sem() will print out the buffered messages
+                 * console_unlock(); will print out the buffered messages
                  * for us.
                  */
                 spin_lock_irqsave(&logbuf_lock, flags);
                 con_start = log_start;
                 spin_unlock_irqrestore(&logbuf_lock, flags);
+                /*
+                 * We're about to replay the log buffer.  Only do this to the
+                 * just-registered console to avoid excessive message spam to
+                 * the already-registered consoles.
+                 */
+                exclusive_console = newcon;
         }
-        release_console_sem();
+        console_unlock();
+        console_sysfs_notify();
 
         /*
          * By unregistering the bootconsoles after we enable the real console
@@ -1355,7 +1532,9 @@ void register_console(struct console *newcon)
          * users know there might be something in the kernel's log buffer that
          * went to the bootconsole (that they do not see on the real console)
          */
-        if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
+        if (bcon &&
+            ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
+            !keep_bootcon) {
                 /* we need to iterate through twice, to make sure we print
                  * everything out, before we unregister the console(s)
                  */
@@ -1382,7 +1561,7 @@ int unregister_console(struct console *console)
                 return braille_unregister_console(console);
 #endif
 
-        acquire_console_sem();
+        console_lock();
         if (console_drivers == console) {
                 console_drivers=console->next;
                 res = 0;
@@ -1404,7 +1583,8 @@ int unregister_console(struct console *console)
         if (console_drivers != NULL && console->flags & CON_CONSDEV)
                 console_drivers->flags |= CON_CONSDEV;
 
-        release_console_sem();
+        console_unlock();
+        console_sysfs_notify();
         return res;
 }
 EXPORT_SYMBOL(unregister_console);
@@ -1488,7 +1668,7 @@ int kmsg_dump_register(struct kmsg_dumper *dumper)
         /* Don't allow registering multiple times */
         if (!dumper->registered) {
                 dumper->registered = 1;
-                list_add_tail(&dumper->list, &dump_list);
+                list_add_tail_rcu(&dumper->list, &dump_list);
                 err = 0;
         }
         spin_unlock_irqrestore(&dump_list_lock, flags);
@@ -1512,29 +1692,16 @@ int kmsg_dump_unregister(struct kmsg_dumper *dumper)
         spin_lock_irqsave(&dump_list_lock, flags);
         if (dumper->registered) {
                 dumper->registered = 0;
-                list_del(&dumper->list);
+                list_del_rcu(&dumper->list);
                 err = 0;
         }
         spin_unlock_irqrestore(&dump_list_lock, flags);
+        synchronize_rcu();
 
         return err;
 }
 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
 
-static const char const *kmsg_reasons[] = {
-        [KMSG_DUMP_OOPS]        = "oops",
-        [KMSG_DUMP_PANIC]       = "panic",
-        [KMSG_DUMP_KEXEC]       = "kexec",
-};
-
-static const char *kmsg_to_str(enum kmsg_dump_reason reason)
-{
-        if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
-                return "unknown";
-
-        return kmsg_reasons[reason];
-}
-
 /**
  * kmsg_dump - dump kernel log to kernel message dumpers.
  * @reason: the reason (oops, panic etc) for dumping
@@ -1573,13 +1740,9 @@ void kmsg_dump(enum kmsg_dump_reason reason)
                 l2 = chars;
         }
 
-        if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
-                printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
-                                kmsg_to_str(reason));
-                return;
-        }
-        list_for_each_entry(dumper, &dump_list, list)
+        rcu_read_lock();
+        list_for_each_entry_rcu(dumper, &dump_list, list)
                 dumper->dump(dumper, reason, s1, l1, s2, l2);
-        spin_unlock_irqrestore(&dump_list_lock, flags);
+        rcu_read_unlock();
 }
 #endif