I claim the ornamental design for a barbecue smoker, as shown and described.
FIG. 1 is an exploded perspective view of a barbecue smoker of the present invention, illustrating a removable top as detached from the invention and smoker drawers in extended positions;
FIG. 2 is a front elevational view of the invention, illustrating the top as attached to the invention and the smoker drawers in retracted positions;
FIG. 3 is a rear elevational view of the invention, illustrating the top as attached to the invention and the smoker drawers in their retracted positions;
FIG. 4 is a right-side elevational view of the invention, illustrating the top as attached to the invention and the smoker drawers in their retracted positions;
FIG. 5 is a left-side elevational view of the invention, illustrating the top as attached to the invention and the smoker drawers in their retracted positions; and,
FIG. 6 is a top plan view of the invention, illustrating the smoker drawers in their retracted positions.
The bottom plan view is not visible during normal use and does not constitute a part of the claimed design.