[PATCH] kernel/delayacct.c: check NULL for member variable 'delays' in all extern functions.

[Chen Gang]

The member variable 'delays' may be NULL, so need check NULL before use
it for all extern functions, just like __delayacct_tsk_init() and
__delayacct_add_tsk() have already done.


Signed-off-by: Chen Gang <gang.c...@asianux.com>
---
 kernel/delayacct.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index d473988..10cddce 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -81,11 +81,15 @@ static void delayacct_end(struct timespec *start, struct 
timespec *end,
 
 void __delayacct_blkio_start(void)
 {
+       if (!current->delays)
+               return;
        delayacct_start(&current->delays->blkio_start);
 }
 
 void __delayacct_blkio_end(void)
 {
+       if (!current->delays)
+               return;
        if (current->delays->flags & DELAYACCT_PF_SWAPIN)
                /* Swapin block I/O */
                delayacct_end(&current->delays->blkio_start,
@@ -167,6 +171,8 @@ __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
        __u64 ret;
        unsigned long flags;
 
+       if (!tsk->delays)
+               return 0;
        spin_lock_irqsave(&tsk->delays->lock, flags);
        ret = nsec_to_clock_t(tsk->delays->blkio_delay +
                                tsk->delays->swapin_delay);
@@ -176,11 +182,15 @@ __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 
 void __delayacct_freepages_start(void)
 {
+       if (!current->delays)
+               return;
        delayacct_start(&current->delays->freepages_start);
 }
 
 void __delayacct_freepages_end(void)
 {
+       if (!current->delays)
+               return;
        delayacct_end(&current->delays->freepages_start,
                        &current->delays->freepages_end,
                        &current->delays->freepages_delay,
-- 
1.7.7.6
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