[bug report] drm/amdgpu: add function to creat all ras debugfs node

From: Dan Carpenter <dan.carpenter@oracle.com>
To: tao.zhou1@amd.com
Cc: amd-gfx@lists.freedesktop.org
Subject: [bug report] drm/amdgpu: add function to creat all ras debugfs node
Date: Thu, 12 Mar 2020 10:33:51 +0300	[thread overview]
Message-ID: <20200312073351.GA29451@mwanda> (raw)

Hello Tao Zhou,

The patch f9317014ea51: "drm/amdgpu: add function to creat all ras
debugfs node" from Mar 6, 2020, leads to the following static checker
warning:

	drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c:1132 amdgpu_ras_debugfs_create_all()
	warn: variable dereferenced before check 'obj' (see line 1131)

drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
  1116  void amdgpu_ras_debugfs_create_all(struct amdgpu_device *adev)
  1117  {
  1118          struct amdgpu_ras *con = amdgpu_ras_get_context(adev);
  1119          struct ras_manager *obj, *tmp;
  1120          struct ras_fs_if fs_info;
  1121  
  1122          /*
  1123           * it won't be called in resume path, no need to check
  1124           * suspend and gpu reset status
  1125           */
  1126          if (!con)
  1127                  return;
  1128  
  1129          amdgpu_ras_debugfs_create_ctrl_node(adev);
  1130  
  1131          list_for_each_entry_safe(obj, tmp, &con->head, node) {
  1132                  if (!obj)
                            ^^^^
There is no need to check for NULL here, so just remove the check.  The
other question is why is this using list_for_each_entry_safe() instead
of vanilla list_for_each_entry()?  It doesn't seem to be freeing "obj"
or removing "obj" from the list which are basically the only reasons
why _safe() is used.  Some people think _safe() has something to do with
locking but it doesn't.

Please remove the test and use vanilla list_for_each_entry().

  1133                          continue;
  1134  
  1135                  if (amdgpu_ras_is_supported(adev, obj->head.block) &&
  1136                          (obj->attr_inuse == 1)) {
  1137                          sprintf(fs_info.debugfs_name, "%s_err_inject",
  1138                                          ras_block_str(obj->head.block));
  1139                          fs_info.head = obj->head;
  1140                          amdgpu_ras_debugfs_create(adev, &fs_info);
  1141                  }
  1142          }
  1143  }

regards,
dan carpenter
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