ANDROID: uid_sys_stat: fix data-error of cputime and io

'commit b6115e14 ("ANDROID: uid_sys_stat: split the global
lock uid_lock to the fine-grained locks for each hlist in hash_table.")'

The above patch split the global lock to per-uid lock to reduce lock
competition. But result in data-error from uid_cputime_show and uid_io_show in
some cases.

E.g, if thread1 and thread2 read /proc/uid_cputime/show_uid_stat at the same time,
thread2 maybe operate in partA and zero active_stime and active_utime of uid_entry
when thread1 is between partB and partC, which would cause thread1 show the error data.
static int uid_cputime_show(struct seq_file *m, void *v)
{
	...
	/*partA*/
	for (bkt = 0, uid_entry = NULL; uid_entry == NULL &&
		bkt < HASH_SIZE(hash_table); bkt++) {
		lock_uid_by_bkt(bkt);
		hlist_for_each_entry(uid_entry, &hash_table[bkt], hash) {
			uid_entry->active_stime = 0;
			uid_entry->active_utime = 0;
		}
		unlock_uid_by_bkt(bkt);
	}

	rcu_read_lock();
	/* partB */
	do_each_thread(temp, task) {
		...
		lock_uid(uid);
		if (!(task->flags & PF_EXITING)) {
			task_cputime_adjusted(task, &utime, &stime);
			uid_entry->active_utime += utime;
			uid_entry->active_stime += stime;
		}
		unlock_uid(uid);
	} while_each_thread(temp, task);
	rcu_read_unlock();

	for (bkt = 0, uid_entry = NULL; uid_entry == NULL &&
		bkt < HASH_SIZE(hash_table); bkt++) {
		lock_uid_by_bkt(bkt);
		hlist_for_each_entry(uid_entry, &hash_table[bkt], hash) {
			u64 total_utime = uid_entry->utime +
						uid_entry->active_utime;
			u64 total_stime = uid_entry->stime +
						uid_entry->active_stime;
			/* partC */
			seq_printf(m, "%d: %llu %llu\n", uid_entry->uid,
				ktime_to_us(total_utime), ktime_to_us(total_stime));
		}
		unlock_uid_by_bkt(bkt);
	}

The patch ensures that the calculation and seq_printf of each uid_entry is within
the uid_lock range, in order to accurate data.

Bug: 278138377

Change-Id: Iaa2ccd95c4b4b333f04b2ba18d7699d94017394e
Signed-off-by: lipeifeng <lipeifeng@oppo.com>
(cherry picked from commit ea35d2bd)