On Wed, 2014-08-20 at 06:15 -0600, Glenn Golden wrote: > Tanu Kaskinen <tanu.kaskinen at linux.intel.com> [2014-08-20 13:26:19 +0300]: > > > > (added pulseaudio-discuss back to CC) > > > Thx, I hit the wrong button on the reply earlier. > > > > > On Tue, 2014-08-19 at 16:26 -0600, Glenn Golden wrote: > > > This is completely misleading: The test that is performed by the --check > > > option evidently has _nothing whatsoever_ to do with the "calling user", > > > it is determined entirely by the XDG_RUNTIME_DIR envar, regardless of the > > > user who executed the "pulaseaudio --check" command. The blurb should > > > simply state that the check is performed based on the user whose runtime > > > pid dir is pointed to by XDG_RUNTIME_DIR, and then it will be entirely > > > accurate and complete. > > > > I'd rather say that the check is performed with the assumption that > > XDG_RUNTIME_DIR is set correctly for the calling user. > > > > But that phrasing simply introduces a subtler ambiguity: What does "set > correctly" mean in the context of a calling user who has used (e.g.) su(1) > or runuser(1) or an SUID executable to switch UID or EUID? > > Example: A process can be running with UID = xyz, EUID = 0, and so accesss > would be allowed to all /run/user/* directories, not just the directory of > user xyz. Who is the "correct" user in this situation? > > Otoh, simply stating that "the test is performed based on XDG_RUNTIME_DIR" > without any further qualification provides the reader with both the necessary > and sufficient information to inform him as to how the check is performed. > Let the reader infer what he wishes about the notion of "correctness" of > the setting of XDG_RUNTIME_DIR in his particular situation. > > > > > The check is non-functional if XDG_RUNTIME_DIR points to the wrong directory, > > because the answer will always be "not running", because most likely > > pulseaudio won't have access to the directory that XDG_RUNTIME_DIR points to. > > > > Exactly. So wouldn't it make sense to say just state that in the doc? > > "The check is performed based on the runtime directory specified by > $XDG_RUNTIME_DIR. If this envar points to a directory which is not > accessible to the process owner, then the return code is undefined." > > (Or perhaps "non-zero" instead of "undefined" above, if that is the case.) > > > > > Also, if you're going to mention XDG_RUNTIME_DIR in the documentation, > > you should probably also mention that if XDG_RUNTIME_DIR isn't set at > > all, then the check assumes that HOME[1] is set correctly. > > > > The above does not seem to be the case on my Arch linux setup: In the following > example, the PA daemon is running as user gdg, and yet: > > # id > uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys), \ > 4(adm),6(disk),10(wheel),19(log) > > # su - gdg > $ id > uid=501(gdg) gid=501(gdg) groups=501(gdg),19(log),92(audio), \ > 190(systemd-journal) > $ unset XDG_RUNTIME_DIR > $ echo $HOME > /home/gdg > $ pulseaudio --check -v > I: [pulseaudio] main.c: Daemon not running > > From an xterm which is directly logged in as user gdg, the --check option > correctly reports the daemon info: > > $ id > uid=501(gdg) gid=501(gdg) groups=501(gdg),19(log),92(audio), \ > 190(systemd-journal) > $ echo $HOME > /home/gdg > $ echo $XDG_RUNTIME_DIR > /run/user/501 > $ pulseaudio --check -v > I: [pulseaudio] main.c: Daemon running as PID 29731 > > So... before I submit a doc patch, it would probably be worthwhile to get > hold of a confirmed explanation of exactly what is being done for the check. Unsetting XDG_RUNTIME_DIR thing didn't work, because the pulseaudio instance that was running was started in an environment where XDG_RUNTIME_DIR was set, and it was set to point to /run/user/501, so that directory was used to store the pid file. When you ran pulseaudio --check, XDG_RUNTIME_DIR was not set, so pulseaudio couldn't figure out that it should have used /run/user/501 for the runtime directory. Instead, --check used ~/.config/pulse/f8bba75988c34d26965f9d0486fe30af-runtime, and it didn't find the pid file there. > If you can point me to a sourcefile, I'll try to plumb the details myself, > and then get back to you with my findings and see if you agree before > submitting a doc patch. pa_pid_file_check_running() is in src/pulsecore/pid.c, the runtime directory logic is in src/pulsecore/core-util.c. -- Tanu
