path: root/kernel/delayacct.c
diff options
authorShailabh Nagar <nagar@watson.ibm.com>2006-08-31 21:27:38 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-01 11:39:08 -0700
commit35df17c57cecb08f0120fb18926325f1093dc429 (patch)
treedc79780b3133e55dc591e35238fdb313e8e0219e /kernel/delayacct.c
parent30f3174d1c506db2c6d2c1dddc9c064e741d6b76 (diff)
[PATCH] task delay accounting fixes
Cleanup allocation and freeing of tsk->delays used by delay accounting. This solves two problems reported for delay accounting: 1. oops in __delayacct_blkio_ticks http://www.uwsg.indiana.edu/hypermail/linux/kernel/0608.2/1844.html Currently tsk->delays is getting freed too early in task exit which can cause a NULL tsk->delays to get accessed via reading of /proc/<tgid>/stats. The patch fixes this problem by freeing tsk->delays closer to when task_struct itself is freed up. As a result, it also eliminates the use of tsk->delays_lock which was only being used (inadequately) to safeguard access to tsk->delays while a task was exiting. 2. Possible memory leak in kernel/delayacct.c http://www.uwsg.indiana.edu/hypermail/linux/kernel/0608.2/1389.html The patch cleans up tsk->delays allocations after a bad fork which was missing earlier. The patch has been tested to fix the problems listed above and stress tested with rapid calls to delay accounting's taskstats command interface (which is the other path that can access the same data, besides the /proc interface causing the oops above). Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/delayacct.c')
1 files changed, 0 insertions, 16 deletions
diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index 57ca3730205..36752f124c6 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -41,24 +41,11 @@ void delayacct_init(void)
void __delayacct_tsk_init(struct task_struct *tsk)
- spin_lock_init(&tsk->delays_lock);
- /* No need to acquire tsk->delays_lock for allocation here unless
- __delayacct_tsk_init called after tsk is attached to tasklist
- */
tsk->delays = kmem_cache_zalloc(delayacct_cache, SLAB_KERNEL);
if (tsk->delays)
-void __delayacct_tsk_exit(struct task_struct *tsk)
- struct task_delay_info *delays = tsk->delays;
- spin_lock(&tsk->delays_lock);
- tsk->delays = NULL;
- spin_unlock(&tsk->delays_lock);
- kmem_cache_free(delayacct_cache, delays);
* Start accounting for a delay statistic using
* its starting timestamp (@start)
@@ -118,8 +105,6 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
struct timespec ts;
unsigned long t1,t2,t3;
- spin_lock(&tsk->delays_lock);
/* Though tsk->delays accessed later, early exit avoids
* unnecessary returning of other data
@@ -161,7 +146,6 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
- spin_unlock(&tsk->delays_lock);
return 0;