On 08/22/2013 06:10 AM, Andrew Morton wrote:
> On Tue, 20 Aug 2013 10:40:03 +0800 Chen Gang <gang.c...@asianux.com> wrote:
>
>> 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.
>
> If task.delays is NULL, the kernel will oops. I don't recall seeing
> such oops reports hence I suspect that you missed some check somewhere.
>
> For example, delayacct_blkio_start() checks current->delays before
> calling __delayacct_blkio_start(), so why retest current->delays in
> __delayacct_blkio_start()?
>
>
Hmm... Can we assume "__*" extern function is treated as "should not be
used by outside" ?
If so, the original implementation have done (check NULL before use it
for all extern functions), just like your valuable example, thanks.
Hmm... and better to remove the useless code in __delayacct_add_tsk(),
which the related wrapper function has done, the diff is below:
------------------------------diff begin--------------------------------
diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index d473988..da8b153 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -108,12 +108,6 @@ int __delayacct_add_tsk(struct taskstats *d, struct
task_struct *tsk)
struct timespec ts;
cputime_t utime, stime, stimescaled, utimescaled;
- /* Though tsk->delays accessed later, early exit avoids
- * unnecessary returning of other data
- */
- if (!tsk->delays)
- goto done;
-
tmp = (s64)d->cpu_run_real_total;
task_cputime(tsk, &utime, &stime);
cputime_to_timespec(utime + stime, &ts);
------------------------------diff end----------------------------------
If this diff is OK, I will send related patch for it.
Thanks.
--
Chen Gang
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