Re: [PATCH v1 2/3] scsi: ufs: Optimize host lock on transfer requests send/compl paths

Hi Can,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on mkp-scsi/for-next]
[also build test WARNING on next-20210524]
[cannot apply to scsi/for-next v5.13-rc3]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Can-Guo/Optimize-host-lock-on-TR-send-compl-paths-and-utilize-UTRLCNR/20210524-163847
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git for-next
config: arm64-randconfig-r011-20210524 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 93d1e5822ed64abd777eb94ea9899e96c4c39fbe)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # https://github.com/0day-ci/linux/commit/efe94162bf7973be4ed6496871b9bc9ea54e2819
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Can-Guo/Optimize-host-lock-on-TR-send-compl-paths-and-utilize-UTRLCNR/20210524-163847
        git checkout efe94162bf7973be4ed6496871b9bc9ea54e2819
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All warnings (new ones prefixed by >>):

quoted

drivers/scsi/ufs/ufshcd.c:2959:6: warning: variable 'lrbp' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]

           if (unlikely(test_bit(tag, &hba->outstanding_reqs))) {
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:78:22: note: expanded from macro 'unlikely'
   # define unlikely(x)    __builtin_expect(!!(x), 0)
                           ^~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/scsi/ufs/ufshcd.c:2981:32: note: uninitialized use occurs here
                                       (struct utp_upiu_req *)lrbp->ucd_rsp_ptr);
                                                              ^~~~
   drivers/scsi/ufs/ufshcd.c:2959:2: note: remove the 'if' if its condition is always false
           if (unlikely(test_bit(tag, &hba->outstanding_reqs))) {
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/scsi/ufs/ufshcd.c:2939:25: note: initialize the variable 'lrbp' to silence this warning
           struct ufshcd_lrb *lrbp;
                                  ^
                                   = NULL
   1 warning generated.


vim +2959 drivers/scsi/ufs/ufshcd.c

  2924	
  2925	/**
  2926	 * ufshcd_exec_dev_cmd - API for sending device management requests
  2927	 * @hba: UFS hba
  2928	 * @cmd_type: specifies the type (NOP, Query...)
  2929	 * @timeout: time in seconds
  2930	 *
  2931	 * NOTE: Since there is only one available tag for device management commands,
  2932	 * it is expected you hold the hba->dev_cmd.lock mutex.
  2933	 */
  2934	static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
  2935			enum dev_cmd_type cmd_type, int timeout)
  2936	{
  2937		struct request_queue *q = hba->cmd_queue;
  2938		struct request *req;
  2939		struct ufshcd_lrb *lrbp;
  2940		int err;
  2941		int tag;
  2942		struct completion wait;
  2943	
  2944		down_read(&hba->clk_scaling_lock);
  2945	
  2946		/*
  2947		 * Get free slot, sleep if slots are unavailable.
  2948		 * Even though we use wait_event() which sleeps indefinitely,
  2949		 * the maximum wait time is bounded by SCSI request timeout.
  2950		 */
  2951		req = blk_get_request(q, REQ_OP_DRV_OUT, 0);
  2952		if (IS_ERR(req)) {
  2953			err = PTR_ERR(req);
  2954			goto out_unlock;
  2955		}
  2956		tag = req->tag;
  2957		WARN_ON_ONCE(!ufshcd_valid_tag(hba, tag));
  2958	

2959		if (unlikely(test_bit(tag, &hba->outstanding_reqs))) {

  2960			err = -EBUSY;
  2961			goto out;
  2962		}
  2963	
  2964		init_completion(&wait);
  2965		lrbp = &hba->lrb[tag];
  2966		WARN_ON(lrbp->cmd);
  2967		err = ufshcd_compose_dev_cmd(hba, lrbp, cmd_type, tag);
  2968		if (unlikely(err))
  2969			goto out_put_tag;
  2970	
  2971		hba->dev_cmd.complete = &wait;
  2972	
  2973		ufshcd_add_query_upiu_trace(hba, UFS_QUERY_SEND, lrbp->ucd_req_ptr);
  2974		/* Make sure descriptors are ready before ringing the doorbell */
  2975		wmb();
  2976	
  2977		ufshcd_send_command(hba, tag);
  2978		err = ufshcd_wait_for_dev_cmd(hba, lrbp, timeout);
  2979	out:
  2980		ufshcd_add_query_upiu_trace(hba, err ? UFS_QUERY_ERR : UFS_QUERY_COMP,
  2981					    (struct utp_upiu_req *)lrbp->ucd_rsp_ptr);
  2982	
  2983	out_put_tag:
  2984		blk_put_request(req);
  2985	out_unlock:
  2986		up_read(&hba->clk_scaling_lock);
  2987		return err;
  2988	}
  2989	

---
0-DAY CI Kernel Test Service, Intel Corporation
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