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>

diff --git a/arch/um/Kconfig.debug b/arch/um/Kconfig.debug
index 09c1aca6339f94cf629a419387eff7f4f2517820..c86f5eb29fd584619a807e4c10520a40fa81b6eb 100644 (file)
--- a/arch/um/Kconfig.debug
+++ b/arch/um/Kconfig.debug
@@ -47,4 +47,13 @@ config GCOV
         If you're involved in UML kernel development and want to use gcov,
         say Y.  If you're unsure, say N.
 
+config DEBUG_STACK_USAGE
+       bool "Stack utilization instrumentation"
+       default N
+       help
+         Track the maximum kernel stack usage - this will look at each
+         kernel stack at process exit and log it if it's the deepest
+         stack seen so far.
+
+         This option will slow down process creation and destruction somewhat.
 endmenu

diff --git a/arch/um/defconfig b/arch/um/defconfig
index a54d0efecae1567074ca28ec77edcb70e8bb88ae..e5b2df9e12de07e0bfdec8ac4209eedf1ac3d2a2 100644 (file)
--- a/arch/um/defconfig
+++ b/arch/um/defconfig
@@ -527,3 +527,4 @@ CONFIG_FORCED_INLINING=y
 # CONFIG_RCU_TORTURE_TEST is not set
 # CONFIG_GPROF is not set
 # CONFIG_GCOV is not set
+# CONFIG_DEBUG_STACK_USAGE is not set

diff --git a/include/asm-um/thread_info.h b/include/asm-um/thread_info.h
index 07aa4e50e4d04635b2e41b5e132cd8b452ae91ff..6e5fd5c892d069439ed56191d837df54dd94dd58 100644 (file)
--- a/include/asm-um/thread_info.h
+++ b/include/asm-um/thread_info.h
@@ -52,10 +52,19 @@ static inline struct thread_info *current_thread_info(void)
        return ti;
 }
 
+#ifdef CONFIG_DEBUG_STACK_USAGE
+
+#define alloc_thread_info(tsk) \
+       ((struct thread_info *) __get_free_pages(GFP_KERNEL | __GFP_ZERO, \
+                                                CONFIG_KERNEL_STACK_ORDER))
+#else
+
 /* thread information allocation */
 #define alloc_thread_info(tsk) \
        ((struct thread_info *) __get_free_pages(GFP_KERNEL, \
                                                 CONFIG_KERNEL_STACK_ORDER))
+#endif
+
 #define free_thread_info(ti) \
        free_pages((unsigned long)(ti),CONFIG_KERNEL_STACK_ORDER)
 

diff --git a/kernel/exit.c b/kernel/exit.c
index ca6a11b730231bd0d6d9ece041e1a2f537223582..64a5263c8c7bde37339aeaf784b4a59134c16fbb 100644 (file)
--- 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);