8c98be6c36
Add 'lock' file under daemon base and flock it, so only one perf daemon can run on top of it. Each daemon tries to create and lock BASE/lock file, if it's successful we are sure we're the only daemon running over the BASE. Once daemon is finished, file descriptor to lock file is closed and lock is released. Example: # cat ~/.perfconfig [daemon] base=/opt/perfdata [session-cycles] run = -m 10M -e cycles --overwrite --switch-output -a [session-sched] run = -m 20M -e sched:* --overwrite --switch-output -a Starting the daemon: # perf daemon start And try once more: # perf daemon start failed: another perf daemon (pid 775594) owns /opt/perfdata will end up with an error, because there's already one running on top of /opt/perfdata. Committer notes: Provide lockf(F_TLOCK) when not available, i.e. transform: lockf(fd, F_TLOCK, 0); into: flock(fd, LOCK_EX | LOCK_NB); Which should be equivalent. Noticed when cross building to some odd Android NDK. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alexei Budankov <abudankov@huawei.com> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Michael Petlan <mpetlan@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: https://lore.kernel.org/r/20210208200908.1019149-14-jolsa@kernel.org 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 Restructured Text 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.