linux-kernel - Re: [PATCH v12 15/17] counter: Implement events_queue

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Message-ID: <202107060033.5eN2wc37-lkp@intel.com>
Date:   Tue, 6 Jul 2021 10:48:31 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        jic23@...nel.org
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-stm32@...md-mailman.stormreply.com, kernel@...gutronix.de,
        a.fatoum@...gutronix.de, kamel.bouhara@...tlin.com,
        gwendal@...omium.org, alexandre.belloni@...tlin.com,
        david@...hnology.com, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 15/17] counter: Implement events_queue_size sysfs
 attribute

Hi William,

url:    https://github.com/0day-ci/linux/commits/William-Breathitt-Gray/Introduce-the-Counter-character-device-interface/20210705-162324
base:   6cbb3aa0f9d5d23221df787cf36f74d3866fdb78
config: parisc-randconfig-m031-20210705 (attached as .config)
compiler: hppa-linux-gcc (GCC) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

smatch warnings:
drivers/counter/counter-sysfs.c:815 counter_events_queue_size_write() warn: inconsistent returns '&counter->chrdev_lock'.

vim +815 drivers/counter/counter-sysfs.c

d95f8a2e83a813 William Breathitt Gray 2021-07-05  794  static int counter_events_queue_size_write(struct counter_device *counter,
d95f8a2e83a813 William Breathitt Gray 2021-07-05  795  					   u64 val)
d95f8a2e83a813 William Breathitt Gray 2021-07-05  796  {
d95f8a2e83a813 William Breathitt Gray 2021-07-05  797  	int err;
d95f8a2e83a813 William Breathitt Gray 2021-07-05  798  	DECLARE_KFIFO_PTR(events, struct counter_event);
d95f8a2e83a813 William Breathitt Gray 2021-07-05  799  
d95f8a2e83a813 William Breathitt Gray 2021-07-05  800  	/* Verify chrdev is not currently being used */
d95f8a2e83a813 William Breathitt Gray 2021-07-05  801  	if (!mutex_trylock(&counter->chrdev_lock))
d95f8a2e83a813 William Breathitt Gray 2021-07-05  802  		return -EBUSY;
d95f8a2e83a813 William Breathitt Gray 2021-07-05  803  
d95f8a2e83a813 William Breathitt Gray 2021-07-05  804  	/* Allocate new events queue */
d95f8a2e83a813 William Breathitt Gray 2021-07-05  805  	err = kfifo_alloc(&events, val, GFP_ATOMIC);
d95f8a2e83a813 William Breathitt Gray 2021-07-05  806  	if (err)
d95f8a2e83a813 William Breathitt Gray 2021-07-05  807  		return err;

Drop the lock.  With a mutex the alloc() doesn't necessarily have to
ATOMIC by the way.

d95f8a2e83a813 William Breathitt Gray 2021-07-05  808  
d95f8a2e83a813 William Breathitt Gray 2021-07-05  809  	/* Swap in new events queue */
d95f8a2e83a813 William Breathitt Gray 2021-07-05  810  	kfifo_free(&counter->events);
d95f8a2e83a813 William Breathitt Gray 2021-07-05  811  	counter->events.kfifo = events.kfifo;
d95f8a2e83a813 William Breathitt Gray 2021-07-05  812  
d95f8a2e83a813 William Breathitt Gray 2021-07-05  813  	mutex_unlock(&counter->chrdev_lock);
d95f8a2e83a813 William Breathitt Gray 2021-07-05  814  
d95f8a2e83a813 William Breathitt Gray 2021-07-05 @815  	return 0;
d95f8a2e83a813 William Breathitt Gray 2021-07-05  816  }

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org