Because pthread failures are virtually undebuggable (which sure is
pretty strange, given all these heavy instrumentation tools these days).
Of course it affects only files which include osdep/threads.h.
I'm departing from the usual way to add symbols with config.h and using
"#if", and defining it on the compiler command line + "#ifdef" because I
don't want to include config.h from a header (which would be necessary
in this case) to keep things slightly cleaner. Maybe this is misguided,
but still.
This would have been easier if mpv defined its own wrappers for all
thread functions. But we don't (which to be honest is probably better
than e.g. going crazy like VLC and essentially reimplementing
everything). This seems to be a good compromise. Since it's off by
default and basically a developer tool, the minor undefined behavior
(redefining reserved symbols) isn't much of an issue.
This reverts commit 2e81698d28.
Seems like this was a patch applied from someone who can't agree to LGPL
relicensing (see previous commit), with the author field not properly
set.
This is not so important anyway, so just revert it.
Windows, as of the Creators Update, finally has a sane API for giving a
name to a thread that can be used by debuggers. This is similar to
pthread_setname_np on Linux and some Unixes. Expose it in the pthread
wrapper and use it for mpthread_set_name().
This covers source files which were added in mplayer2 and mpv times
only, and where all code is covered by LGPL relicensing agreements.
There are probably more files to which this applies, but I'm being
conservative here.
A file named ao_sdl.c exists in MPlayer too, but the mpv one is a
complete rewrite, and was added some time after the original ao_sdl.c
was removed. The same applies to vo_sdl.c, for which the SDL2 API is
radically different in addition (MPlayer supports SDL 1.2 only).
common.c contains only code written by me. But common.h is a strange
case: although it originally was named mp_common.h and exists in MPlayer
too, by now it contains only definitions written by uau and me. The
exceptions are the CONTROL_ defines - thus not changing the license of
common.h yet.
codec_tags.c contained once large tables generated from MPlayer's
codecs.conf, but all of these tables were removed.
From demux_playlist.c I'm removing a code fragment from someone who was
not asked; this probably could be done later (see commit 15dccc37).
misc.c is a bit complicated to reason about (it was split off mplayer.c
and thus contains random functions out of this file), but actually all
functions have been added post-MPlayer. Except get_relative_time(),
which was written by uau, but looks similar to 3 different versions of
something similar in each of the Unix/win32/OSX timer source files. I'm
not sure what that means in regards to copyright, so I've just moved it
into another still-GPL source file for now.
screenshot.c once had some minor parts of MPlayer's vf_screenshot.c, but
they're all gone.
There is not much of a reason to have these wrappers around. Use POSIX
standard functions directly, and use a separate utility function to take
care of the timespec calculations. (Course POSIX for using this weird
format for time values.)
It turns out the glibc people are very clever and return an error if the
thread name exceeds the maximum supported kernel length, instead of
truncating the name. So everyone has to hardcode the currently allowed
Linux kernel name length limit, even if it gets extended later.
Also the Lua script filenames could get too long; use the client name
instead.
Another strange thing is that on Linux, unrelated threads "inherit" the
name by the thread they were created. This leads to random thread names,
because there's not necessarily a strong relation between these threads
(e.g. script command leads to filter recreation -> the filter's threads
are tagged with the script's thread name). Unfortunate.
Especially with other components (libavcodec, OSX stuff), the thread
list can get quite populated. Setting the thread name helps when
debugging.
Since this is not portable, we check the OS variants in waf configure.
old-configure just gets a special-case for glibc, since doing a full
check here would probably be a waste of effort.
Use the time as returned by mp_time_us() for mpthread_cond_timedwait(),
instead of calculating the struct timespec value based on a timeout.
This (probably) makes it easier to wait for a specific deadline.
This was part of osdep/threads.c out of laziness. But it doesn't contain
anything OS dependent. Note that the rest of threads.c actually isn't
all that OS dependent either (just some minor ifdeffery to work around
the lack of clock_gettime() on OSX).
When passing a very large timeout to mpthread_cond_timed_wait(), the
calculations could overflow, setting tv_sec to a negative value, and
making the pthread_cond_timed_wait() call return immediately. This
accidentally made Lua support poll and burn CPU for no reason.
The existing overflow check was ineffective on 32 bit systems. tv_sec is
usually a long, so adding INT_MAX to it will usually not overflow on 64
bit systems, but on 32 bit systems it's guaranteed to overflow. Simply
fix by clamping against a relatively high value. This will work until 1
week before the UNIX time wraps around in 32 bits.
It's quite possible to overflow the calculation by setting the timeout
to high values. Limit it to INT_MAX, which should be safe. The issue is
mainly the secs variable.
timespec.tv_sec will normally be 64 bit on sane systems, and we assume
it can't overflow by adding INT_MAX to it.
Usually, you have to call pthread_cond_timedwait() in a loop (because it
can wake up sporadically). If this function is used by another higher
level function, which uses a relative timeout, we actually have to
reduce the timeout on each iteration - or, simpler, compute the
"deadline" at the beginning of the function, and always pass the same
absolute time to the waiting function.
Might be unsafe if the system time is changed. On the other hand, this
is a fundamental race condition with these APIs.
wm4
James Ross-Gowan