Add generic exit-time stack-depth checking to CONFIG_DEBUG_STACK_USAGE

Add generic exit-time stack-depth checking to CONFIG_DEBUG_STACK_USAGE.

This also adds UML support.

Tested on UML and i386.

[akpm@linux-foundation.org: cleanups, speedups, tweaks]
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index ca6a11b73023..64a5263c8c7b 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -858,6 +858,34 @@ static void exit_notify(struct task_struct *tsk)
                 release_task(tsk);
 }
 
+#ifdef CONFIG_DEBUG_STACK_USAGE
+static void check_stack_usage(void)
+{
+        static DEFINE_SPINLOCK(low_water_lock);
+        static int lowest_to_date = THREAD_SIZE;
+        unsigned long *n = end_of_stack(current);
+        unsigned long free;
+
+        while (*n == 0)
+                n++;
+        free = (unsigned long)n - (unsigned long)end_of_stack(current);
+
+        if (free >= lowest_to_date)
+                return;
+
+        spin_lock(&low_water_lock);
+        if (free < lowest_to_date) {
+                printk(KERN_WARNING "%s used greatest stack depth: %lu bytes "
+                                "left\n",
+                                current->comm, free);
+                lowest_to_date = free;
+        }
+        spin_unlock(&low_water_lock);
+}
+#else
+static inline void check_stack_usage(void) {}
+#endif
+
 fastcall NORET_TYPE void do_exit(long code)
 {
         struct task_struct *tsk = current;
@@ -949,6 +977,7 @@ fastcall NORET_TYPE void do_exit(long code)
         exit_sem(tsk);
         __exit_files(tsk);
         __exit_fs(tsk);
+        check_stack_usage();
         exit_thread();
         cpuset_exit(tsk);
         exit_keys(tsk);