Merge remote-tracking branch 'torvalds/master' into perf/core

To pick up fixes.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 10 insertions, 38 deletions

diff --git a/lib/dump_stack.c b/lib/dump_stack.c
index f5a33b6f773f..27f16872320d 100644
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@ -73,10 +73,10 @@ void show_regs_print_info(const char *log_lvl)
 	dump_stack_print_info(log_lvl);
 }
 
-static void __dump_stack(void)
+static void __dump_stack(const char *log_lvl)
 {
-	dump_stack_print_info(KERN_DEFAULT);
-	show_stack(NULL, NULL, KERN_DEFAULT);
+	dump_stack_print_info(log_lvl);
+	show_stack(NULL, NULL, log_lvl);
 }
 
 /**
@@ -84,50 +84,22 @@ static void __dump_stack(void)
  *
  * Architectures can override this implementation by implementing its own.
  */
-#ifdef CONFIG_SMP
-static atomic_t dump_lock = ATOMIC_INIT(-1);
-
-asmlinkage __visible void dump_stack(void)
+asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
 {
 	unsigned long flags;
-	int was_locked;
-	int old;
-	int cpu;
 
 	/*
 	 * Permit this cpu to perform nested stack dumps while serialising
 	 * against other CPUs
 	 */
-retry:
-	local_irq_save(flags);
-	cpu = smp_processor_id();
-	old = atomic_cmpxchg(&dump_lock, -1, cpu);
-	if (old == -1) {
-		was_locked = 0;
-	} else if (old == cpu) {
-		was_locked = 1;
-	} else {
-		local_irq_restore(flags);
-		/*
-		 * Wait for the lock to release before jumping to
-		 * atomic_cmpxchg() in order to mitigate the thundering herd
-		 * problem.
-		 */
-		do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
-		goto retry;
-	}
-
-	__dump_stack();
-
-	if (!was_locked)
-		atomic_set(&dump_lock, -1);
-
-	local_irq_restore(flags);
+	printk_cpu_lock_irqsave(flags);
+	__dump_stack(log_lvl);
+	printk_cpu_unlock_irqrestore(flags);
 }
-#else
+EXPORT_SYMBOL(dump_stack_lvl);
+
 asmlinkage __visible void dump_stack(void)
 {
-	__dump_stack();
+	dump_stack_lvl(KERN_DEFAULT);
 }
-#endif
 EXPORT_SYMBOL(dump_stack);