tools/bpftool: Fix build slowdown

Commit ba2fd56 ("tools/bpftool: Support passing BPFTOOL_VERSION to make") changed BPFTOOL_VERSION to a recursively expanded variable, forcing it to be recomputed on every expansion of CFLAGS and dramatically slowing down the bpftool build. Restore BPFTOOL_VERSION as a simply expanded variable, guarded by an ifeq(). Fixes: ba2fd56 ("tools/bpftool: Support passing BPFTOOL_VERSION to make") Signed-off-by: Jean-Philippe Brucker <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
kawasaki · Nov 11, 2020 · 0639e5e · 0639e5e
1 parent 2d9393f
commit 0639e5e
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
@@ -30,7 +30,9 @@ LIBBPF = $(LIBBPF_PATH)libbpf.a
 LIBBPF_BOOTSTRAP_OUTPUT = $(BOOTSTRAP_OUTPUT)libbpf/
 LIBBPF_BOOTSTRAP = $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
 
-BPFTOOL_VERSION ?= $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
+ifeq ($(BPFTOOL_VERSION),)
+BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
+endif
 
 $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT):
 	$(QUIET_MKDIR)mkdir -p $@