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Commit 1e57c218 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'core-fixes-for-linus' of... 

Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  lockdep: Avoid out of bounds array reference in save_trace()
  futex: Take mmap_sem for get_user_pages in fault_in_user_writeable
  lockstat: Add usage info to Documentation/lockstat.txt
  lockstat: Fix min, max times in /proc/lock_stats
parents 75630098 ea5b41f9

Documentation/lockstat.txt

+12 −0
Original line number Diff line number Diff line
@@ -62,8 +62,20 @@ applicable). 
It also tracks 4 contention points per class. A contention point is a call site

that had to wait on lock acquisition.



 - CONFIGURATION



Lock statistics are enabled via CONFIG_LOCK_STATS.



 - USAGE



Enable collection of statistics:



# echo 1 >/proc/sys/kernel/lock_stat



Disable collection of statistics:



# echo 0 >/proc/sys/kernel/lock_stat



Look at the current lock statistics:



( line numbers not part of actual output, done for clarity in the explanation

kernel/futex.c

+8 −2
Original line number Diff line number Diff line
@@ -304,8 +304,14 @@ void put_futex_key(int fshared, union futex_key *key) 
 */

static int fault_in_user_writeable(u32 __user *uaddr)

{

	int ret = get_user_pages(current, current->mm, (unsigned long)uaddr,

	struct mm_struct *mm = current->mm;

	int ret;



	down_read(&mm->mmap_sem);

	ret = get_user_pages(current, mm, (unsigned long)uaddr,

			     1, 1, 0, NULL, NULL);

	up_read(&mm->mmap_sem);



	return ret < 0 ? ret : 0;

}

kernel/lockdep.c

+12 −4
Original line number Diff line number Diff line
@@ -168,7 +168,7 @@ static void lock_time_inc(struct lock_time *lt, u64 time) 
	if (time > lt->max)

		lt->max = time;



	if (time < lt->min || !lt->min)

	if (time < lt->min || !lt->nr)

		lt->min = time;



	lt->total += time;
@@ -177,8 +177,15 @@ static void lock_time_inc(struct lock_time *lt, u64 time) 


static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)

{

	dst->min += src->min;

	dst->max += src->max;

	if (!src->nr)

		return;



	if (src->max > dst->max)

		dst->max = src->max;



	if (src->min < dst->min || !dst->nr)

		dst->min = src->min;



	dst->total += src->total;

	dst->nr += src->nr;

}
@@ -379,7 +386,8 @@ static int save_trace(struct stack_trace *trace) 
	 * complete trace that maxes out the entries provided will be reported

	 * as incomplete, friggin useless </rant>

	 */

	if (trace->entries[trace->nr_entries-1] == ULONG_MAX)

	if (trace->nr_entries != 0 &&

	    trace->entries[trace->nr_entries-1] == ULONG_MAX)

		trace->nr_entries--;



	trace->max_entries = trace->nr_entries;