1 files changed, 36 insertions, 7 deletions

diff --git a/kernel/panic.c b/kernel/panic.c
index b26593604214..80aed44e345a 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -49,6 +49,15 @@ static long no_blink(int state)
 long (*panic_blink)(int state);
 EXPORT_SYMBOL(panic_blink);
 
+/*
+ * Stop ourself in panic -- architecture code may override this
+ */
+void __weak panic_smp_self_stop(void)
+{
+        while (1)
+                cpu_relax();
+}
+
 /**
  *      panic - halt the system
  *      @fmt: The text string to print
@@ -57,8 +66,9 @@ EXPORT_SYMBOL(panic_blink);
  *
  *      This function never returns.
  */
-NORET_TYPE void panic(const char * fmt, ...)
+void panic(const char *fmt, ...)
 {
+        static DEFINE_SPINLOCK(panic_lock);
         static char buf[1024];
         va_list args;
         long i, i_next = 0;
@@ -68,8 +78,14 @@ NORET_TYPE void panic(const char * fmt, ...)
          * It's possible to come here directly from a panic-assertion and
          * not have preempt disabled. Some functions called from here want
          * preempt to be disabled. No point enabling it later though...
+         *
+         * Only one CPU is allowed to execute the panic code from here. For
+         * multiple parallel invocations of panic, all other CPUs either
+         * stop themself or will wait until they are stopped by the 1st CPU
+         * with smp_send_stop().
          */
-        preempt_disable();
+        if (!spin_trylock(&panic_lock))
+                panic_smp_self_stop();
 
         console_verbose();
         bust_spinlocks(1);
@@ -78,7 +94,11 @@ NORET_TYPE void panic(const char * fmt, ...)
         va_end(args);
         printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
 #ifdef CONFIG_DEBUG_BUGVERBOSE
-        dump_stack();
+        /*
+         * Avoid nested stack-dumping if a panic occurs during oops processing
+         */
+        if (!oops_in_progress)
+                dump_stack();
 #endif
 
         /*
@@ -237,11 +257,20 @@ void add_taint(unsigned flag)
          * Can't trust the integrity of the kernel anymore.
          * We don't call directly debug_locks_off() because the issue
          * is not necessarily serious enough to set oops_in_progress to 1
-         * Also we want to keep up lockdep for staging development and
-         * post-warning case.
+         * Also we want to keep up lockdep for staging/out-of-tree
+         * development and post-warning case.
          */
-        if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off())
-                printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
+        switch (flag) {
+        case TAINT_CRAP:
+        case TAINT_OOT_MODULE:
+        case TAINT_WARN:
+        case TAINT_FIRMWARE_WORKAROUND:
+                break;
+
+        default:
+                if (__debug_locks_off())
+                        printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
+        }
 
         set_bit(flag, &tainted_mask);
 }