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b48543c451
When executing the command "perf list", I met "Error: failed to open tracing events directory" twice, the first reason is that there is no "/sys/kernel/tracing/events" directory due to it does not enable the kernel tracing infrastructure with CONFIG_FTRACE, the second reason is that there is no root privileges. Add the error string to tell the users what happened and what should to do, and also call put_tracing_file() to free events_path a little later to avoid messy code in the error message. At the same time, just remove the redundant "/" of the file path in the function get_tracing_file(), otherwise it shows something like "/sys/kernel/tracing//events". Before: $ ./perf list Error: failed to open tracing events directory After: (1) Without CONFIG_FTRACE $ ./perf list Error: failed to open tracing events directory /sys/kernel/tracing/events: No such file or directory (2) With CONFIG_FTRACE but no root privileges $ ./perf list Error: failed to open tracing events directory /sys/kernel/tracing/events: Permission denied Committer testing: Redirect stdout to null to quickly test the patch: Before: $ perf list > /dev/null Error: failed to open tracing events directory $ After: $ perf list > /dev/null Error: failed to open tracing events directory /sys/kernel/tracing/events: Permission denied $ Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/lkml/20240730062301.23244-3-yangtiezhu@loongson.cn Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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.