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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
parent30f3174d1c506db2c6d2c1dddc9c064e741d6b76 (diff)
downloadlinux-35df17c57cecb08f0120fb18926325f1093dc429.tar.gz
[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>
-rw-r--r--include/linux/delayacct.h10
-rw-r--r--include/linux/sched.h1
-rw-r--r--kernel/delayacct.c16
-rw-r--r--kernel/exit.c1
-rw-r--r--kernel/fork.c6
5 files changed, 11 insertions, 23 deletions
diff --git a/include/linux/delayacct.h b/include/linux/delayacct.h
index 11487b6e712..561e2a77805 100644
--- a/include/linux/delayacct.h
+++ b/include/linux/delayacct.h
@@ -59,10 +59,14 @@ static inline void delayacct_tsk_init(struct task_struct *tsk)
__delayacct_tsk_init(tsk);
}
-static inline void delayacct_tsk_exit(struct task_struct *tsk)
+/* Free tsk->delays. Called from bad fork and __put_task_struct
+ * where there's no risk of tsk->delays being accessed elsewhere
+ */
+static inline void delayacct_tsk_free(struct task_struct *tsk)
{
if (tsk->delays)
- __delayacct_tsk_exit(tsk);
+ kmem_cache_free(delayacct_cache, tsk->delays);
+ tsk->delays = NULL;
}
static inline void delayacct_blkio_start(void)
@@ -101,7 +105,7 @@ static inline void delayacct_init(void)
{}
static inline void delayacct_tsk_init(struct task_struct *tsk)
{}
-static inline void delayacct_tsk_exit(struct task_struct *tsk)
+static inline void delayacct_tsk_free(struct task_struct *tsk)
{}
static inline void delayacct_blkio_start(void)
{}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6674fc1e51b..34ed0d99b1b 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -994,7 +994,6 @@ struct task_struct {
*/
struct pipe_inode_info *splice_pipe;
#ifdef CONFIG_TASK_DELAY_ACCT
- spinlock_t delays_lock;
struct task_delay_info *delays;
#endif
};
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)
spin_lock_init(&tsk->delays->lock);
}
-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);
done:
- spin_unlock(&tsk->delays_lock);
return 0;
}
diff --git a/kernel/exit.c b/kernel/exit.c
index dba194a8d41..a4c19a52ce4 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -908,7 +908,6 @@ fastcall NORET_TYPE void do_exit(long code)
audit_free(tsk);
taskstats_exit_send(tsk, tidstats, group_dead, mycpu);
taskstats_exit_free(tidstats);
- delayacct_tsk_exit(tsk);
exit_mm(tsk);
diff --git a/kernel/fork.c b/kernel/fork.c
index aa36c43783c..f9b014e3e70 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -117,6 +117,7 @@ void __put_task_struct(struct task_struct *tsk)
security_task_free(tsk);
free_uid(tsk->user);
put_group_info(tsk->group_info);
+ delayacct_tsk_free(tsk);
if (!profile_handoff_task(tsk))
free_task(tsk);
@@ -1011,7 +1012,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
retval = -EFAULT;
if (clone_flags & CLONE_PARENT_SETTID)
if (put_user(p->pid, parent_tidptr))
- goto bad_fork_cleanup;
+ goto bad_fork_cleanup_delays_binfmt;
INIT_LIST_HEAD(&p->children);
INIT_LIST_HEAD(&p->sibling);
@@ -1277,7 +1278,8 @@ bad_fork_cleanup_policy:
bad_fork_cleanup_cpuset:
#endif
cpuset_exit(p);
-bad_fork_cleanup:
+bad_fork_cleanup_delays_binfmt:
+ delayacct_tsk_free(p);
if (p->binfmt)
module_put(p->binfmt->module);
bad_fork_cleanup_put_domain: