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Building perf in-tree is broken after commit890a1961c8("perf tools: Create source symlink in perf object dir") which added a 'source' symlink in the output dir pointing to the source dir. With in-tree builds, the added 'SOURCE = ...' line is executed multiple times (I observed 2 during the build plus 2 during installation). This is a minor inefficiency, in theory not harmful because symlink creation is assumed to be idempotent. But it is not. Considering with in-tree builds: srctree=/absolute/path/to/linux OUTPUT=/absolute/path/to/linux/tools/perf here's what happens: 1. ln -sf $(srctree)/tools/perf $(OUTPUT)/source -> creates /absolute/path/to/linux/tools/perf/source link to /absolute/path/to/linux/tools/perf => OK, that's what was intended 2. ln -sf $(srctree)/tools/perf $(OUTPUT)/source # same command as 1 -> creates /absolute/path/to/linux/tools/perf/perf link to /absolute/path/to/linux/tools/perf => Not what was intended, not idempotent 3. Now the build _should_ create the 'perf' executable, but it fails The reason is the tricky 'ln' command line. At the first invocation 'ln' uses the 1st form: ln [OPTION]... [-T] TARGET LINK_NAME and creates a link to TARGET *called LINK_NAME*. At the second invocation $(OUTPUT)/source exists, so 'ln' uses the 3rd form: ln [OPTION]... TARGET... DIRECTORY and creates a link to TARGET *called TARGET* inside DIRECTORY. Fix by adding -n/--no-dereference to "treat LINK_NAME as a normal file if it is a symbolic link to a directory", as the manpage says. Closes: https://lore.kernel.org/all/20241125182506.38af9907@booty/ Fixes:890a1961c8("perf tools: Create source symlink in perf object dir") Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com> Reviewed-by: Charlie Jenkins <charlie@rivosinc.com> Tested-by: Charlie Jenkins <charlie@rivosinc.com> Link: https://lore.kernel.org/r/20250124-perf-fix-intree-build-v1-1-485dd7a855e4@bootlin.com Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.