From e18eecb8b35703a5eea73ee2b45324262029e62c Mon Sep 17 00:00:00 2001
From: Jeff Dike <jdike@addtoit.com>
Date: Sun, 15 Jul 2007 23:38:48 -0700
Subject: [PATCH] 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>
---
arch/um/Kconfig.debug | 9 +++++++++
arch/um/defconfig | 1 +
include/asm-um/thread_info.h | 9 +++++++++
kernel/exit.c | 29 +++++++++++++++++++++++++++++
4 files changed, 48 insertions(+)
diff --git a/arch/um/Kconfig.debug b/arch/um/Kconfig.debug
index 09c1aca6339f..c86f5eb29fd5 100644
--- 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 a54d0efecae1..e5b2df9e12de 100644
--- 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 07aa4e50e4d0..6e5fd5c892d0 100644
--- 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 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);
--
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