Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Remove hacks to allow libkse to export its symbols in the LIBTHREAD_1_0
version namespace which was needed before the library version was
bumped.

WARNS=3'ify.

Repo copy libpthreads to libkse.
This introduces the WITHOUT_LIBKSE nob,
and changes WITHOUT_LIBPTHREADS to mean with neither threading libs.
Approved by: re(kensmith)

Remove 3rd clause, renumber, ok per email

Add compatibility symbol maps. libpthread (.so.1 and .so.2)
used LIBTHREAD_1_0 as its version definition, but now needs
to define its symbols in the same namespace used by libc.
The compatibility hooks allows you to use libraries and
binaries built and linked to libpthread before libc was
built with symbol versioning. The shims can be removed if
libpthread is given a version bump.

Reviewed by: davidxu

Rename _thr_enter_cancellation_point to _thr_cancel_enter, rename
_thr_leave_cancellation_point to _thr_cancel_leave, add a parameter
to _thr_cancel_leave to indicate whether cancellation point should be
checked, this gives us an option to not check cancallation point if
a syscall successfully returns to avoid any leaks, current I have
creat(), open() and fcntl(F_DUPFD) to not check cancellation point
after they sucessfully returned.

Replace some members in structure kse with bit flags to same some
memory.

Conditionally compile THR_ASSERT to nothing if _PTHREAD_INVARIANTS is
not defined.

Inline some small functions in thr_cancel.c.

Use __predict_false in thr_kern.c for some executed only once code.

Reviewd by: deischen

Revamp libpthread so that it has a chance of working in an SMP
environment. This includes support for multiple KSEs and KSEGs.

The ability to create more than 1 KSE via pthread_setconcurrency()
is in the works as well as support for PTHREAD_SCOPE_SYSTEM threads.
Those should come shortly.

There are still some known issues which davidxu and I are working
on, but it'll make it easier for us by committing what we have.

This library now passes all of the ACE tests that libc_r passes
with the exception of one. It also seems to work OK with KDE
including konqueror, kwrite, etc. I haven't been able to get
mozilla to run due to lack of java plugin, so I'd be interested
to see how it works with that.

Reviewed by: davidxu

Make libpthread KSE aware.

Reviewed by: deischen, julian
Approved by: -arch

Make the changes needed for libpthread to compile in its new home.
The new libpthread will provide POSIX threading support using KSE.
These files were previously repo-copied from src/lib/libc_r.

Reviewed by: deischen
Approved by: -arch

Remove much of the dereferencing of the fd table entries to look
at file flags and replace it with functions that will avoid null
pointer checks.

MFC to be done by archie ;-)

PR: 42100
Reviewed by: archie, robert
MFC after: 3 days

Make these functions cancellation points like they should be:
poll(2), readv(2), select(2), wait4(2), writev(2).

PR: bin/37658
Reviewed by: deischen
MFC after: 1 week

To be consistent, use the __weak_reference macro from <sys/cdefs.h>
instead of #pragma weak to create weak definitions.

Suggested by: bde

Add weak definitions for wrapped system calls. In general:

_foo - wrapped system call
foo - weak definition to _foo

and for cancellation points:

_foo - wrapped system call
__foo - enter cancellation point, call _foo(), leave
cancellation point
foo - weak definition to __foo

Change use of global _thread_run to call a function to get the
currently running thread.

Make all pthread_foo functions weak definitions to _pthread_foo,
where _pthread_foo is the implementation. This allows an application
to provide its own pthread functions.

Provide slightly different versions of pthread_mutex_lock and
pthread_mutex_init so that we can tell the difference between
a libc mutex and an application mutex. Threads holding mutexes
internal to libc should never be allowed to exit, call signal
handlers, or cancel.

Approved by: -arch

Use __strong_reference() instead of __weak_reference() to assure that the
weak symbols of the same name are not used.

Simplify sytem call renaming. Instead of _foo() <-- _libc_foo <-- foo(),
just use _foo() <-- foo(). In the case of a libpthread that doesn't do
call conversion (such as linuxthreads and our upcoming libpthread), this
is adequate. In the case of libc_r, we still need three names, which are
now _thread_sys_foo() <-- _foo() <-- foo().

Convert all internal libc usage of: aio_suspend(), close(), fsync(), msync(),
nanosleep(), open(), fcntl(), read(), and write() to _foo() instead of foo().

Remove all internal libc usage of: creat(), pause(), sleep(), system(),
tcdrain(), wait(), and waitpid().

Make thread cancellation fully POSIX-compliant.

Suggested by: deischen

Track libc's three-tier symbol naming. libc_r must currently implement
the _libc_*() entry points and add *() weak aliases. This will all
change for the better when libc_r becomes libpthread.

$Id$ -> $FreeBSD$

Add RCS IDs to those files without them.
Fix copyrights (s/REGENTS/AUTHOR).

Suggested by: tg
Approved by: jb

Check the access mode in the flags before waiting on a read or a write
that might never be possible if the file was not opened in the corrent
mode. This prevents a hang for bad programs. Why do people code like that?

Implement compile time debug support instead of tracking file name and
line number every time a file descriptor is locked.

This looks like a big change but it isn't. It should reduce the size
of libc_r and make it run slightly faster.

Change signal model to match POSIX (i.e. one set of signal handlers
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!

Add parentheses to make blocking mode work.

Submitted by: John Birrell
uthreads update from the author.

Reviewed by: julian
Submitted by: john birrel

One version of the pthreads library
another will follow with differnt actions under some cases..
not QUITE complete