Merge tag 'v3.10.103' into update

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / kernel / printk.c

diff --git a/kernel/printk.c b/kernel/printk.c
index 617bc0d08e2b77ae53b7b6ea28700f3298b9b891..f23cbc5e9ea31f2fae57235e5c6827c812fba296 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -2131,7 +2131,7 @@ void console_unlock(void)
        static u64 seen_seq;
        unsigned long flags;
        bool wake_klogd = false;
-       bool retry;
+       bool do_cond_resched, retry;
 #ifdef LOG_TOO_MUCH_WARNING
     unsigned long total_log_size = 0;
     unsigned long long t1 = 0, t2 = 0;
@@ -2139,11 +2139,23 @@ void console_unlock(void)
     int org_loglevel = console_loglevel;
 #endif
 
+
        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 */
@@ -2239,6 +2251,9 @@ skip:
         call_console_drivers(level, text, len);
 #endif
                local_irq_restore(flags);
+
+               if (do_cond_resched)
+                       cond_resched();
        }
        console_locked = 0;
        mutex_release(&console_lock_dep_map, 1, _RET_IP_);
@@ -2307,6 +2322,25 @@ 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
  */