* [vfs:work.epoll 17/27] fs/eventpoll.c:1629:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing
@ 2020-10-26 2:09 kernel test robot
2020-10-26 2:35 ` Al Viro
0 siblings, 1 reply; 3+ messages in thread
From: kernel test robot @ 2020-10-26 2:09 UTC (permalink / raw)
To: Al Viro; +Cc: kbuild-all, linux-fsdevel
tree: https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.epoll
head: 319c15174757aaedacc89a6e55c965416f130e64
commit: ff07952aeda8563d5080da3a0754db83ed0650f6 [17/27] ep_send_events_proc(): fold into the caller
compiler: h8300-linux-gcc (GCC) 9.3.0
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
"cppcheck warnings: (new ones prefixed by >>)"
>> fs/eventpoll.c:1629:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing it? [uselessAssignmentPtrArg]
events++;
^
vim +1629 fs/eventpoll.c
1565
1566 static int ep_send_events(struct eventpoll *ep,
1567 struct epoll_event __user *events, int maxevents)
1568 {
1569 struct epitem *epi, *tmp;
1570 LIST_HEAD(txlist);
1571 poll_table pt;
1572 int res = 0;
1573
1574 init_poll_funcptr(&pt, NULL);
1575
1576 ep_start_scan(ep, 0, false, &txlist);
1577
1578 /*
1579 * We can loop without lock because we are passed a task private list.
1580 * Items cannot vanish during the loop because ep_scan_ready_list() is
1581 * holding "mtx" during this call.
1582 */
1583 lockdep_assert_held(&ep->mtx);
1584
1585 list_for_each_entry_safe(epi, tmp, &txlist, rdllink) {
1586 struct wakeup_source *ws;
1587 __poll_t revents;
1588
1589 if (res >= maxevents)
1590 break;
1591
1592 /*
1593 * Activate ep->ws before deactivating epi->ws to prevent
1594 * triggering auto-suspend here (in case we reactive epi->ws
1595 * below).
1596 *
1597 * This could be rearranged to delay the deactivation of epi->ws
1598 * instead, but then epi->ws would temporarily be out of sync
1599 * with ep_is_linked().
1600 */
1601 ws = ep_wakeup_source(epi);
1602 if (ws) {
1603 if (ws->active)
1604 __pm_stay_awake(ep->ws);
1605 __pm_relax(ws);
1606 }
1607
1608 list_del_init(&epi->rdllink);
1609
1610 /*
1611 * If the event mask intersect the caller-requested one,
1612 * deliver the event to userspace. Again, ep_scan_ready_list()
1613 * is holding ep->mtx, so no operations coming from userspace
1614 * can change the item.
1615 */
1616 revents = ep_item_poll(epi, &pt, 1);
1617 if (!revents)
1618 continue;
1619
1620 if (__put_user(revents, &events->events) ||
1621 __put_user(epi->event.data, &events->data)) {
1622 list_add(&epi->rdllink, &txlist);
1623 ep_pm_stay_awake(epi);
1624 if (!res)
1625 res = -EFAULT;
1626 break;
1627 }
1628 res++;
> 1629 events++;
1630 if (epi->event.events & EPOLLONESHOT)
1631 epi->event.events &= EP_PRIVATE_BITS;
1632 else if (!(epi->event.events & EPOLLET)) {
1633 /*
1634 * If this file has been added with Level
1635 * Trigger mode, we need to insert back inside
1636 * the ready list, so that the next call to
1637 * epoll_wait() will check again the events
1638 * availability. At this point, no one can insert
1639 * into ep->rdllist besides us. The epoll_ctl()
1640 * callers are locked out by
1641 * ep_scan_ready_list() holding "mtx" and the
1642 * poll callback will queue them in ep->ovflist.
1643 */
1644 list_add_tail(&epi->rdllink, &ep->rdllist);
1645 ep_pm_stay_awake(epi);
1646 }
1647 }
1648 ep_done_scan(ep, 0, false, &txlist);
1649
1650 return res;
1651 }
1652
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [vfs:work.epoll 17/27] fs/eventpoll.c:1629:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing
2020-10-26 2:09 [vfs:work.epoll 17/27] fs/eventpoll.c:1629:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing kernel test robot
@ 2020-10-26 2:35 ` Al Viro
2020-10-26 9:45 ` [kbuild-all] " Rong Chen
0 siblings, 1 reply; 3+ messages in thread
From: Al Viro @ 2020-10-26 2:35 UTC (permalink / raw)
To: kernel test robot; +Cc: kbuild-all, linux-fsdevel
On Mon, Oct 26, 2020 at 10:09:47AM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.epoll
> head: 319c15174757aaedacc89a6e55c965416f130e64
> commit: ff07952aeda8563d5080da3a0754db83ed0650f6 [17/27] ep_send_events_proc(): fold into the caller
> compiler: h8300-linux-gcc (GCC) 9.3.0
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
>
> "cppcheck warnings: (new ones prefixed by >>)"
> >> fs/eventpoll.c:1629:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing it? [uselessAssignmentPtrArg]
> events++;
> ^
Who the hell has come up with that warning? What happens is,
essentially,
f(..., events, ....)
loop in which we have
g(events, something); // store the next sample
events++;
More specifically, it's
> 1620 if (__put_user(revents, &events->events) ||
> 1621 __put_user(epi->event.data, &events->data)) {
> 1622 list_add(&epi->rdllink, &txlist);
> 1623 ep_pm_stay_awake(epi);
> 1624 if (!res)
> 1625 res = -EFAULT;
> 1626 break;
> 1627 }
> 1628 res++;
> > 1629 events++;
If anything, that should be reported to the maintainers of the buggy code.
Which is not the kernel in this case.
Google search on that thing brings this:
Cppcheck is an analysis tool for C/C++ code. It detects the types of
bugs that the compilers normally fail to detect. The goal is no false positives.
IOW, that should be reported to the authors of that thing, seeing that
their stated goal is obviously missed in this case. Badly. Assignments of
function parameters can be perfectly idiomatic and this case is such.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [kbuild-all] Re: [vfs:work.epoll 17/27] fs/eventpoll.c:1629:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing
2020-10-26 2:35 ` Al Viro
@ 2020-10-26 9:45 ` Rong Chen
0 siblings, 0 replies; 3+ messages in thread
From: Rong Chen @ 2020-10-26 9:45 UTC (permalink / raw)
To: Al Viro, kernel test robot; +Cc: kbuild-all, linux-fsdevel
On 10/26/20 10:35 AM, Al Viro wrote:
> On Mon, Oct 26, 2020 at 10:09:47AM +0800, kernel test robot wrote:
>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.epoll
>> head: 319c15174757aaedacc89a6e55c965416f130e64
>> commit: ff07952aeda8563d5080da3a0754db83ed0650f6 [17/27] ep_send_events_proc(): fold into the caller
>> compiler: h8300-linux-gcc (GCC) 9.3.0
>>
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kernel test robot <lkp@intel.com>
>>
>>
>> "cppcheck warnings: (new ones prefixed by >>)"
>>>> fs/eventpoll.c:1629:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing it? [uselessAssignmentPtrArg]
>> events++;
>> ^
> Who the hell has come up with that warning? What happens is,
> essentially,
>
> f(..., events, ....)
> loop in which we have
> g(events, something); // store the next sample
> events++;
>
> More specifically, it's
>> 1620 if (__put_user(revents, &events->events) ||
>> 1621 __put_user(epi->event.data, &events->data)) {
>> 1622 list_add(&epi->rdllink, &txlist);
>> 1623 ep_pm_stay_awake(epi);
>> 1624 if (!res)
>> 1625 res = -EFAULT;
>> 1626 break;
>> 1627 }
>> 1628 res++;
>>> 1629 events++;
> If anything, that should be reported to the maintainers of the buggy code.
> Which is not the kernel in this case.
>
> Google search on that thing brings this:
>
> Cppcheck is an analysis tool for C/C++ code. It detects the types of
> bugs that the compilers normally fail to detect. The goal is no false positives.
>
> IOW, that should be reported to the authors of that thing, seeing that
> their stated goal is obviously missed in this case. Badly. Assignments of
> function parameters can be perfectly idiomatic and this case is such.
Hi Al,
Thanks for the explanation, we'll avoid sending out such reports
automatically
and double check the warning.
Best Regards,
Rong Chen
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-10-26 10:15 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-26 2:09 [vfs:work.epoll 17/27] fs/eventpoll.c:1629:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing kernel test robot
2020-10-26 2:35 ` Al Viro
2020-10-26 9:45 ` [kbuild-all] " Rong Chen
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).