drivers/block/rnbd/rnbd-clt.c:247:20: sparse: sparse: context imbalance in 'rnbd_rerun_if_needed' - different lock contexts for basic block

drivers/block/rnbd/rnbd-clt.c:247:20: sparse: sparse: context imbalance in 'rnbd_rerun_if_needed' - different lock contexts for basic block

[kernel test robot]

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CC: kbuild-all(a)lists.01.org
CC: linux-kernel(a)vger.kernel.org
TO: Jack Wang <jinpu.wang@cloud.ionos.com>
CC: Jason Gunthorpe <jgg@mellanox.com>
CC: Danil Kipnis <danil.kipnis@cloud.ionos.com>
CC: Bart Van Assche <bvanassche@acm.org>

Hi Jack,

First bad commit (maybe != root cause):

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   2d743660786ec51f5c1fefd5782bbdee7b227db0
commit: bc01885342e193e7943d86ccbd7bc3e8fee50a68 block/rnbd: include client and server modules into kernel compilation
date:   11 months ago
:::::: branch date: 13 hours ago
:::::: commit date: 11 months ago
config: powerpc-randconfig-s032-20210407 (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.3-279-g6d5d9b42-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bc01885342e193e7943d86ccbd7bc3e8fee50a68
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout bc01885342e193e7943d86ccbd7bc3e8fee50a68
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=powerpc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


sparse warnings: (new ones prefixed by >>)
>> drivers/block/rnbd/rnbd-clt.c:247:20: sparse: sparse: context imbalance in 'rnbd_rerun_if_needed' - different lock contexts for basic block

vim +/rnbd_rerun_if_needed +247 drivers/block/rnbd/rnbd-clt.c

f7a7a5c228d45e Jack Wang 2020-05-11  217  
f7a7a5c228d45e Jack Wang 2020-05-11  218  /**
f7a7a5c228d45e Jack Wang 2020-05-11  219   * rnbd_rerun_if_needed() - rerun next queue marked as stopped
f7a7a5c228d45e Jack Wang 2020-05-11  220   * @sess:	Session to rerun a queue on
f7a7a5c228d45e Jack Wang 2020-05-11  221   *
f7a7a5c228d45e Jack Wang 2020-05-11  222   * Description:
f7a7a5c228d45e Jack Wang 2020-05-11  223   *     Each CPU has it's own list of HW queues, which should be rerun.
f7a7a5c228d45e Jack Wang 2020-05-11  224   *     Function finds such list with HW queues, takes a list lock, picks up
f7a7a5c228d45e Jack Wang 2020-05-11  225   *     the first HW queue out of the list and requeues it.
f7a7a5c228d45e Jack Wang 2020-05-11  226   *
f7a7a5c228d45e Jack Wang 2020-05-11  227   * Return:
f7a7a5c228d45e Jack Wang 2020-05-11  228   *     True if the queue was requeued, false otherwise.
f7a7a5c228d45e Jack Wang 2020-05-11  229   *
f7a7a5c228d45e Jack Wang 2020-05-11  230   * Context:
f7a7a5c228d45e Jack Wang 2020-05-11  231   *     Does not matter.
f7a7a5c228d45e Jack Wang 2020-05-11  232   */
f7a7a5c228d45e Jack Wang 2020-05-11  233  static bool rnbd_rerun_if_needed(struct rnbd_clt_session *sess)
f7a7a5c228d45e Jack Wang 2020-05-11  234  {
f7a7a5c228d45e Jack Wang 2020-05-11  235  	struct rnbd_queue *q = NULL;
f7a7a5c228d45e Jack Wang 2020-05-11  236  	struct rnbd_cpu_qlist *cpu_q;
f7a7a5c228d45e Jack Wang 2020-05-11  237  	unsigned long flags;
f7a7a5c228d45e Jack Wang 2020-05-11  238  	int *cpup;
f7a7a5c228d45e Jack Wang 2020-05-11  239  
f7a7a5c228d45e Jack Wang 2020-05-11  240  	/*
f7a7a5c228d45e Jack Wang 2020-05-11  241  	 * To keep fairness and not to let other queues starve we always
f7a7a5c228d45e Jack Wang 2020-05-11  242  	 * try to wake up someone else in round-robin manner.  That of course
f7a7a5c228d45e Jack Wang 2020-05-11  243  	 * increases latency but queues always have a chance to be executed.
f7a7a5c228d45e Jack Wang 2020-05-11  244  	 */
f7a7a5c228d45e Jack Wang 2020-05-11  245  	cpup = get_cpu_ptr(sess->cpu_rr);
f7a7a5c228d45e Jack Wang 2020-05-11  246  	for (cpu_q = rnbd_get_cpu_qlist(sess, nxt_cpu(*cpup)); cpu_q;
f7a7a5c228d45e Jack Wang 2020-05-11 @247  	     cpu_q = rnbd_get_cpu_qlist(sess, nxt_cpu(cpu_q->cpu))) {
f7a7a5c228d45e Jack Wang 2020-05-11  248  		if (!spin_trylock_irqsave(&cpu_q->requeue_lock, flags))
f7a7a5c228d45e Jack Wang 2020-05-11  249  			continue;
f7a7a5c228d45e Jack Wang 2020-05-11  250  		if (unlikely(!test_bit(cpu_q->cpu, sess->cpu_queues_bm)))
f7a7a5c228d45e Jack Wang 2020-05-11  251  			goto unlock;
f7a7a5c228d45e Jack Wang 2020-05-11  252  		q = list_first_entry_or_null(&cpu_q->requeue_list,
f7a7a5c228d45e Jack Wang 2020-05-11  253  					     typeof(*q), requeue_list);
f7a7a5c228d45e Jack Wang 2020-05-11  254  		if (WARN_ON(!q))
f7a7a5c228d45e Jack Wang 2020-05-11  255  			goto clear_bit;
f7a7a5c228d45e Jack Wang 2020-05-11  256  		list_del_init(&q->requeue_list);
f7a7a5c228d45e Jack Wang 2020-05-11  257  		clear_bit_unlock(0, &q->in_list);
f7a7a5c228d45e Jack Wang 2020-05-11  258  
f7a7a5c228d45e Jack Wang 2020-05-11  259  		if (list_empty(&cpu_q->requeue_list)) {
f7a7a5c228d45e Jack Wang 2020-05-11  260  			/* Clear bit if nothing is left */
f7a7a5c228d45e Jack Wang 2020-05-11  261  clear_bit:
f7a7a5c228d45e Jack Wang 2020-05-11  262  			clear_bit(cpu_q->cpu, sess->cpu_queues_bm);
f7a7a5c228d45e Jack Wang 2020-05-11  263  		}
f7a7a5c228d45e Jack Wang 2020-05-11  264  unlock:
f7a7a5c228d45e Jack Wang 2020-05-11  265  		spin_unlock_irqrestore(&cpu_q->requeue_lock, flags);
f7a7a5c228d45e Jack Wang 2020-05-11  266  
f7a7a5c228d45e Jack Wang 2020-05-11  267  		if (q)
f7a7a5c228d45e Jack Wang 2020-05-11  268  			break;
f7a7a5c228d45e Jack Wang 2020-05-11  269  	}
f7a7a5c228d45e Jack Wang 2020-05-11  270  
f7a7a5c228d45e Jack Wang 2020-05-11  271  	/**
f7a7a5c228d45e Jack Wang 2020-05-11  272  	 * Saves the CPU that is going to be requeued on the per-cpu var. Just
f7a7a5c228d45e Jack Wang 2020-05-11  273  	 * incrementing it doesn't work because rnbd_get_cpu_qlist() will
f7a7a5c228d45e Jack Wang 2020-05-11  274  	 * always return the first CPU with something on the queue list when the
f7a7a5c228d45e Jack Wang 2020-05-11  275  	 * value stored on the var is greater than the last CPU with something
f7a7a5c228d45e Jack Wang 2020-05-11  276  	 * on the list.
f7a7a5c228d45e Jack Wang 2020-05-11  277  	 */
f7a7a5c228d45e Jack Wang 2020-05-11  278  	if (cpu_q)
f7a7a5c228d45e Jack Wang 2020-05-11  279  		*cpup = cpu_q->cpu;
f7a7a5c228d45e Jack Wang 2020-05-11  280  	put_cpu_var(sess->cpu_rr);
f7a7a5c228d45e Jack Wang 2020-05-11  281  
f7a7a5c228d45e Jack Wang 2020-05-11  282  	if (q)
f7a7a5c228d45e Jack Wang 2020-05-11  283  		rnbd_clt_dev_requeue(q);
f7a7a5c228d45e Jack Wang 2020-05-11  284  
f7a7a5c228d45e Jack Wang 2020-05-11  285  	return q;
f7a7a5c228d45e Jack Wang 2020-05-11  286  }
f7a7a5c228d45e Jack Wang 2020-05-11  287  

:::::: The code at line 247 was first introduced by commit
:::::: f7a7a5c228d45efc45d6e26a199a3ea13d2f8754 block/rnbd: client: main functionality

:::::: TO: Jack Wang <jinpu.wang@cloud.ionos.com>
:::::: CC: Jason Gunthorpe <jgg@mellanox.com>

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

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