All locks are now zero-initialised, so we can drop the G_*_INIT macros
for them.
Adjust various users around GLib accordingly and change the docs.
https://bugzilla.gnome.org/show_bug.cgi?id=659866
asm goto was addded in gcc 4.5 so don't try to use it on gcc versions
older than this one. This is achieved by explicitly checking gcc
version, an alternative would be to try to compile a program using
asm volatile in configure.
https://bugzilla.gnome.org/show_bug.cgi?id=651959
The __sync_fetch_and_or() operation on x86 is a bit suboptimal when the
result isn't ignored. Normally we could use the 'lock or' assembly
instruction to accomplish this, but this instruction discards the
previous value.
In order to work around this issue, GCC is forced to emit a
compare-and-exchange loop.
We can easily use the 'lock bts' instruction, though. It can't be used
in the general case for __sync_fetch_and_or() but it works great for our
case (test and set a single bit).
I filed a bug against GCC[1] to get this exposed as a new intrinsic (or
have the optimiser detect the case) but until then we'll hand-code it on
x86 and amd64.
The uncontended case sees a 31% improvement on my test machine.
[1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49244https://bugzilla.gnome.org/show_bug.cgi?id=651467
Add a performance test for bitlocks.
Make use of the new g_atomic_int_{and,or} to avoid having to do the
usual compare-and-exchange loop.
On a test machine, the change increases performance from approximately
20 million uncontended acquire/releases per second to 31 million.
Commit 22e7fc34c4 introduced a regression:
futexes were always disabled and the emulated codepath was always being
used. That commit was in response to an originally buggy
implementationt hat wrote junk into config.h (but happened to be working
properly).
Fix up the mess and while we're at it, close bug #631231 by including
syscall.h from the correct location and using __NR_futex instead of
SYS_futex.
Closes#631231.
Add support for a mutex lock that consumes only one bit of storage
inside of an integer on systems that support futexes. Futex is emulated
(at a higher cost) on systems that don't have it -- but only in the
contended case.
