linux-kernel - fs/eventpoll.c:526:9: sparse: sparse: restricted __poll

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Date: Tue, 9 Jan 2024 12:45:14 +0800
From: kernel test robot <lkp@...el.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: fs/eventpoll.c:526:9: sparse: sparse: restricted __poll_t degrades
 to integer

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   f0a78b3e2a0c842cc7b4c2686f4a35681f02ca72
commit: caf1aeaffc3b09649a56769e559333ae2c4f1802 eventpoll: add EPOLL_URING_WAKE poll wakeup flag
date:   1 year, 2 months ago
config: i386-randconfig-063-20240105 (https://download.01.org/0day-ci/archive/20240109/202401091221.cupISW8z-lkp@intel.com/config)
compiler: ClangBuiltLinux clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240109/202401091221.cupISW8z-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401091221.cupISW8z-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> fs/eventpoll.c:526:9: sparse: sparse: restricted __poll_t degrades to integer
>> fs/eventpoll.c:526:9: sparse: sparse: cast to restricted __poll_t
>> fs/eventpoll.c:1213:53: sparse: sparse: incorrect type in argument 3 (different base types) @@     expected unsigned int pollflags @@     got restricted __poll_t @@
   fs/eventpoll.c:1213:53: sparse:     expected unsigned int pollflags
   fs/eventpoll.c:1213:53: sparse:     got restricted __poll_t

vim +526 fs/eventpoll.c

   493	
   494	static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi,
   495				     unsigned pollflags)
   496	{
   497		struct eventpoll *ep_src;
   498		unsigned long flags;
   499		u8 nests = 0;
   500	
   501		/*
   502		 * To set the subclass or nesting level for spin_lock_irqsave_nested()
   503		 * it might be natural to create a per-cpu nest count. However, since
   504		 * we can recurse on ep->poll_wait.lock, and a non-raw spinlock can
   505		 * schedule() in the -rt kernel, the per-cpu variable are no longer
   506		 * protected. Thus, we are introducing a per eventpoll nest field.
   507		 * If we are not being call from ep_poll_callback(), epi is NULL and
   508		 * we are at the first level of nesting, 0. Otherwise, we are being
   509		 * called from ep_poll_callback() and if a previous wakeup source is
   510		 * not an epoll file itself, we are at depth 1 since the wakeup source
   511		 * is depth 0. If the wakeup source is a previous epoll file in the
   512		 * wakeup chain then we use its nests value and record ours as
   513		 * nests + 1. The previous epoll file nests value is stable since its
   514		 * already holding its own poll_wait.lock.
   515		 */
   516		if (epi) {
   517			if ((is_file_epoll(epi->ffd.file))) {
   518				ep_src = epi->ffd.file->private_data;
   519				nests = ep_src->nests;
   520			} else {
   521				nests = 1;
   522			}
   523		}
   524		spin_lock_irqsave_nested(&ep->poll_wait.lock, flags, nests);
   525		ep->nests = nests + 1;
 > 526		wake_up_locked_poll(&ep->poll_wait, EPOLLIN | pollflags);
   527		ep->nests = 0;
   528		spin_unlock_irqrestore(&ep->poll_wait.lock, flags);
   529	}
   530	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki