Re: [PATCH] ALSA: pcm: Fix starvation on down_write_nonblock()

From: kbuild test robot <lkp@intel.com>
To: Chanho Min <chanho.min@lge.com>
Cc: kbuild-all@01.org, Jaroslav Kysela <perex@perex.cz>,
	Takashi Iwai <tiwai@suse.com>, Vinod Koul <vinod.koul@intel.com>,
	Daniel Mentz <danielmentz@google.com>,
	linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org,
	Seungho Park <seungho1.park@lge.com>,
	Jongsung Kim <neidhard.kim@lge.com>,
	Wonmin Jung <wonmin.jung@lge.com>, Jaehyun Kim <jehn.kim@lge.com>,
	Hyonwoo Park <hyonwoo.park@lge.com>,
	Chanho Min <chanho.min@lge.com>
Subject: Re: [PATCH] ALSA: pcm: Fix starvation on down_write_nonblock()
Date: Sat, 24 Nov 2018 18:56:54 +0800	[thread overview]
Message-ID: <201811241834.3Ln0lz1L%fengguang.wu@intel.com> (raw)
In-Reply-To: <1543044763-31843-1-git-send-email-chanho.min@lge.com>

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Hi Chanho,

I love your patch! Yet something to improve:

[auto build test ERROR on sound/for-next]
[also build test ERROR on v4.20-rc3 next-20181123]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Chanho-Min/ALSA-pcm-Fix-starvation-on-down_write_nonblock/20181124-182630
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git for-next
config: x86_64-randconfig-x001-201846 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   sound/core/pcm_native.c: In function 'down_write_nonblock':
>> sound/core/pcm_native.c:99:3: error: implicit declaration of function 'msleep' [-Werror=implicit-function-declaration]
      msleep(1);
      ^~~~~~
   cc1: some warnings being treated as errors

vim +/msleep +99 sound/core/pcm_native.c

    89	
    90	/* Writer in rwsem may block readers even during its waiting in queue,
    91	 * and this may lead to a deadlock when the code path takes read sem
    92	 * twice (e.g. one in snd_pcm_action_nonatomic() and another in
    93	 * snd_pcm_stream_lock()).  As a (suboptimal) workaround, let writer to
    94	 * spin until it gets the lock.
    95	 */
    96	static inline void down_write_nonblock(struct rw_semaphore *lock)
    97	{
    98		while (!down_write_trylock(lock))
  > 99			msleep(1);
   100	}
   101	

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