1 files changed, 33 insertions, 8 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 69188f226a93..5052b5497c67 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -32,6 +32,7 @@
 #include <linux/security.h>
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
+#include <linux/kexec.h>
 
 #include <asm/uaccess.h>
 
@@ -73,7 +74,6 @@ EXPORT_SYMBOL(oops_in_progress);
  * driver system.
  */
 static DECLARE_MUTEX(console_sem);
-static DECLARE_MUTEX(secondary_console_sem);
 struct console *console_drivers;
 EXPORT_SYMBOL_GPL(console_drivers);
 
@@ -136,6 +136,24 @@ static char *log_buf = __log_buf;
 static int log_buf_len = __LOG_BUF_LEN;
 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 
+#ifdef CONFIG_KEXEC
+/*
+ * This appends the listed symbols to /proc/vmcoreinfo
+ *
+ * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
+ * obtain access to symbols that are otherwise very difficult to locate.  These
+ * symbols are specifically used so that utilities can access and extract the
+ * dmesg log from a vmcore file after a crash.
+ */
+void log_buf_kexec_setup(void)
+{
+        VMCOREINFO_SYMBOL(log_buf);
+        VMCOREINFO_SYMBOL(log_end);
+        VMCOREINFO_SYMBOL(log_buf_len);
+        VMCOREINFO_SYMBOL(logged_chars);
+}
+#endif
+
 static int __init log_buf_len_setup(char *str)
 {
         unsigned size = memparse(str, &str);
@@ -891,12 +909,14 @@ void suspend_console(void)
         printk("Suspending console(s) (use no_console_suspend to debug)\n");
         acquire_console_sem();
         console_suspended = 1;
+        up(&console_sem);
 }
 
 void resume_console(void)
 {
         if (!console_suspend_enabled)
                 return;
+        down(&console_sem);
         console_suspended = 0;
         release_console_sem();
 }
@@ -912,11 +932,9 @@ void resume_console(void)
 void acquire_console_sem(void)
 {
         BUG_ON(in_interrupt());
-        if (console_suspended) {
-                down(&secondary_console_sem);
-                return;
-        }
         down(&console_sem);
+        if (console_suspended)
+                return;
         console_locked = 1;
         console_may_schedule = 1;
 }
@@ -926,6 +944,10 @@ int try_acquire_console_sem(void)
 {
         if (down_trylock(&console_sem))
                 return -1;
+        if (console_suspended) {
+                up(&console_sem);
+                return -1;
+        }
         console_locked = 1;
         console_may_schedule = 0;
         return 0;
@@ -979,7 +1001,7 @@ void release_console_sem(void)
         unsigned wake_klogd = 0;
 
         if (console_suspended) {
-                up(&secondary_console_sem);
+                up(&console_sem);
                 return;
         }
 
@@ -1289,8 +1311,11 @@ EXPORT_SYMBOL(printk_ratelimit);
 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
                         unsigned int interval_msecs)
 {
-        if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
-                *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
+        if (*caller_jiffies == 0
+                        || !time_in_range(jiffies, *caller_jiffies,
+                                        *caller_jiffies
+                                        + msecs_to_jiffies(interval_msecs))) {
+                *caller_jiffies = jiffies;
                 return true;
         }
         return false;