for the process, not a separate set for each thread). By default, the
process now only has signal handlers installed for SIGVTALRM, SIGINFO
and SIGCHLD. The thread kernel signal handler is installed for other
signals on demand. This means that SIG_IGN and SIG_DFL processing is now
left to the kernel, not the thread kernel.
Change the signal dispatch to no longer use a signal thread, and
call the signal handler using the stack of the thread that has the
signal pending.
Change the atomic lock method to use test-and-set asm code with
a yield if blocked. This introduces separate locks for each type
of object instead of blocking signals to prevent a context
switch. It was this blocking of signals that caused the performance
degradation the people have noted.
This is a *big* change!
it was. Add a FILE_WAIT state and queue threads waiting for a FILE
lock. Start using the sys/queue.h macros instead of the way that MIT
pthreads did it.
Add a thread name to the private thread structure and a non-POSIX
function to set this. This helps (me at least) when sending a SIGINFO
to a threaded process to get a /tmp/uthread.dump to see what the
<expletive deleted> threads are doing this time. It is nice to be
able to recognise (yes, I spell that with an 's' too) which threads
are which.
