Merge branch 'akpm' (patches from Andrew)

Merge second patch-bomb from Andrew Morton:

 - more MM stuff:

    - Kirill's page-flags rework

    - Kirill's now-allegedly-fixed THP rework

    - MADV_FREE implementation

    - DAX feature work (msync/fsync).  This isn't quite complete but DAX
      is new and it's good enough and the guys have a handle on what
      needs to be done - I expect this to be wrapped in the next week or
      two.

  - some vsprintf maintenance work

  - various other misc bits

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (145 commits)
  printk: change recursion_bug type to bool
  lib/vsprintf: factor out %pN[F] handler as netdev_bits()
  lib/vsprintf: refactor duplicate code to special_hex_number()
  printk-formats.txt: remove unimplemented %pT
  printk: help pr_debug and pr_devel to optimize out arguments
  lib/test_printf.c: test dentry printing
  lib/test_printf.c: add test for large bitmaps
  lib/test_printf.c: account for kvasprintf tests
  lib/test_printf.c: add a few number() tests
  lib/test_printf.c: test precision quirks
  lib/test_printf.c: check for out-of-bound writes
  lib/test_printf.c: don't BUG
  lib/kasprintf.c: add sanity check to kvasprintf
  lib/vsprintf.c: warn about too large precisions and field widths
  lib/vsprintf.c: help gcc make number() smaller
  lib/vsprintf.c: expand field_width to 24 bits
  lib/vsprintf.c: eliminate potential race in string()
  lib/vsprintf.c: move string() below widen_string()
  lib/vsprintf.c: pull out padding code from dentry_name()
  printk: do cond_resched() between lines while outputting to consoles
  ...

1 files changed, 62 insertions, 5 deletions

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 2ce8826f1053..e79439134978 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -48,6 +48,7 @@
 #include <linux/uio.h>
 
 #include <asm/uaccess.h>
+#include <asm-generic/sections.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/printk.h>
@@ -1660,7 +1661,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 			    const char *dict, size_t dictlen,
 			    const char *fmt, va_list args)
 {
-	static int recursion_bug;
+	static bool recursion_bug;
 	static char textbuf[LOG_LINE_MAX];
 	char *text = textbuf;
 	size_t text_len = 0;
@@ -1696,7 +1697,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 		 * it can be printed at the next appropriate moment:
 		 */
 		if (!oops_in_progress && !lockdep_recursing(current)) {
-			recursion_bug = 1;
+			recursion_bug = true;
 			local_irq_restore(flags);
 			return 0;
 		}
@@ -1711,7 +1712,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 		static const char recursion_msg[] =
 			"BUG: recent printk recursion!";
 
-		recursion_bug = 0;
+		recursion_bug = false;
 		/* emit KERN_CRIT message */
 		printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
 					 NULL, 0, recursion_msg,
@@ -2233,13 +2234,24 @@ void console_unlock(void)
 	static u64 seen_seq;
 	unsigned long flags;
 	bool wake_klogd = false;
-	bool retry;
+	bool do_cond_resched, retry;
 
 	if (console_suspended) {
 		up_console_sem();
 		return;
 	}
 
+	/*
+	 * Console drivers are called under logbuf_lock, so
+	 * @console_may_schedule should be cleared before; however, we may
+	 * end up dumping a lot of lines, for example, if called from
+	 * console registration path, and should invoke cond_resched()
+	 * between lines if allowable.  Not doing so can cause a very long
+	 * scheduling stall on a slow console leading to RCU stall and
+	 * softlockup warnings which exacerbate the issue with more
+	 * messages practically incapacitating the system.
+	 */
+	do_cond_resched = console_may_schedule;
 	console_may_schedule = 0;
 
 	/* flush buffered message fragment immediately to console */
@@ -2311,6 +2323,9 @@ skip:
 		call_console_drivers(level, ext_text, ext_len, text, len);
 		start_critical_timings();
 		local_irq_restore(flags);
+
+		if (do_cond_resched)
+			cond_resched();
 	}
 	console_locked = 0;
 
@@ -2378,6 +2393,25 @@ void console_unblank(void)
 	console_unlock();
 }
 
+/**
+ * console_flush_on_panic - flush console content on panic
+ *
+ * Immediately output all pending messages no matter what.
+ */
+void console_flush_on_panic(void)
+{
+	/*
+	 * If someone else is holding the console lock, trylock will fail
+	 * and may_schedule may be set.  Ignore and proceed to unlock so
+	 * that messages are flushed out.  As this can be called from any
+	 * context and we don't want to get preempted while flushing,
+	 * ensure may_schedule is cleared.
+	 */
+	console_trylock();
+	console_may_schedule = 0;
+	console_unlock();
+}
+
 /*
  * Return the console tty driver structure and its associated index
  */
@@ -2658,13 +2692,36 @@ int unregister_console(struct console *console)
 }
 EXPORT_SYMBOL(unregister_console);
 
+/*
+ * Some boot consoles access data that is in the init section and which will
+ * be discarded after the initcalls have been run. To make sure that no code
+ * will access this data, unregister the boot consoles in a late initcall.
+ *
+ * If for some reason, such as deferred probe or the driver being a loadable
+ * module, the real console hasn't registered yet at this point, there will
+ * be a brief interval in which no messages are logged to the console, which
+ * makes it difficult to diagnose problems that occur during this time.
+ *
+ * To mitigate this problem somewhat, only unregister consoles whose memory
+ * intersects with the init section. Note that code exists elsewhere to get
+ * rid of the boot console as soon as the proper console shows up, so there
+ * won't be side-effects from postponing the removal.
+ */
 static int __init printk_late_init(void)
 {
 	struct console *con;
 
 	for_each_console(con) {
 		if (!keep_bootcon && con->flags & CON_BOOT) {
-			unregister_console(con);
+			/*
+			 * Make sure to unregister boot consoles whose data
+			 * resides in the init section before the init section
+			 * is discarded. Boot consoles whose data will stick
+			 * around will automatically be unregistered when the
+			 * proper console replaces them.
+			 */
+			if (init_section_intersects(con, sizeof(*con)))
+				unregister_console(con);
 		}
 	}
 	hotcpu_notifier(console_cpu_notify, 0);