- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

MFC r258499:
Fix for the spurious signal handler call with zero signo in the threaded
process.

Approved by: re (hrs)

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

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

Since the cause of the problems with the __fillcontextx() was
identified, unify the code of check_deferred_signal() for all
architectures, making the variant under #ifdef x86 common.

Tested by: marius (sparc64)
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks

The getcontext() from the __fillcontextx() call in the
check_deferred_signal() returns twice, since handle_signal() emulates
the return from the normal signal handler by sigreturn(2)ing the
passed context. Second return is performed on the destroyed stack
frame, because __fillcontextx() has already returned. This causes
undefined and bad behaviour, usually the victim thread gets SIGSEGV.

Avoid nested frame and the need to return from it by doing direct call
to getcontext() in the check_deferred_signal() and using a new private
libc helper __fillcontextx2() to complement the context with the
extended CPU state if the deferred signal is still present.

The __fillcontextx() is now unused, but is kept to allow older
libthr.so to be used with the new libc.

Mark __fillcontextx() as returning twice [1].

Reported by: pgj
Pointy hat to: kib
Discussed with: dim
Tested by: pgj, dim
Suggested by: jilles [1]
MFC after: 1 week

Partially apply the capitalization of the heading word of the sequence
and fix typo.

Sponsored by: The FreeBSD Foundation
MFC after: 1 week

Fix return value for setcontext and swapcontext.

Remove extra code for SA_RESETHAND, it is not needed because kernel has
already done this.

Remove debug code.

Avoid copying memory if SIGCANCEL is not masked.

Revert revision 249323, the PR/177624 is confusing, that bug is caused
by using buggy getcontext/setcontext on same stack, while swapcontext
normally works on different stack, there is no such a problem.

swapcontext wrapper can not be implemented in C, the stack pointer saved in
the context becomes invalid when the function returns, same as setjmp,
it must be implemented in assemble language, see discussions in PR
misc/177624.

In suspend_common(), don't wait for a thread which is in creation, because
pthread_suspend_all_np() may have already suspended its parent thread.
Add locking code in pthread_suspend_all_np() to only allow one thread
to suspend other threads, this eliminates a deadlock where two or more
threads try to suspend each others.

libthr: In the atfork handlers for signals, do not skip the last signal.

_SIG_MAXSIG works a bit unexpectedly: signals 1 till _SIG_MAXSIG are valid,
both bounds inclusive.

Reviewed by: davidxu
MFC after: 1 week

Use getcontextx(3) internal API instead of getcontext(2) to provide
the signal handlers with the context information in the deferrred
case.

Only enable the use of getcontextx(3) in the deferred signal delivery
code on amd64 and i386. Sparc64 seems to have some undetermined issues
with interaction of alloca(3) and signal delivery.

Tested by: flo (who also provided sparc64 harware access for me), pho
Discussed with: marius
MFC after: 1 month

Fix a typo.

Submitted by: avg

Return previous sigaction correctly.

Submitted by: avg

Remove local variable 'first', instead check signal number in memory,
because the variable can be in register, second checking the variable
may still return true, however this is unexpected.

If we are at cancellation point, always work as deferred mode despite
whether asynchronous mode is turned on or not, this always gives us a
chance to decide whether thread should be canceled or not in
cancellation points.

Because atfork lock is held while forking, a thread cancellation triggered
by atfork handler is unsafe, use intenal flag no_cancel to disable it.

Because POSIX does not allow EINTR to be returned from sigwait(),
add a wrapper for it in libc and rework the code in libthr, the
system call still can return EINTR, we keep this feature.

Discussed on: thread
Reviewed by: jilles

Fix off-by-one error in function _thr_sigact_unload, also disable the
function, it seems some gnome application tends to crash if we
unregister sigaction automatically.

Remove incorrect comments, also make sure signal is
disabled when unregistering sigaction.

Add signal handler wrapper, the reason to add it becauses there are
some cases we want to improve:
1) if a thread signal got a signal while in cancellation point,
it is possible the TDP_WAKEUP may be eaten by signal handler
if the handler called some interruptibly system calls.
2) In signal handler, we want to disable cancellation.
3) When thread holding some low level locks, it is better to
disable signal, those code need not to worry reentrancy,
sigprocmask system call is avoided because it is a bit expensive.
The signal handler wrapper works in this way:
1) libthr installs its signal handler if user code invokes sigaction
to install its handler, the user handler is recorded in internal
array.
2) when a signal is delivered, libthr's signal handler is invoke,
libthr checks if thread holds some low level lock or is in critical
region, if it is true, the signal is buffered, and all signals are
masked, once the thread leaves critical region, correct signal
mask is restored and buffered signal is processed.
3) before user signal handler is invoked, cancellation is temporarily
disabled, after user signal handler is returned, cancellation state
is restored, and pending cancellation is rescheduled.

Add wrapper for setcontext() and swapcontext(), the wrappers
unblock SIGCANCEL which is needed by thread cancellation.

Reduce redundant code.

Submitted by: kib

In current implementation, thread cancellation is done in signal handler,
which does not know what is the state of interrupted system call, for
example, open() system call opened a file and the thread is still cancelled,
result is descriptor leak, there are other problems which can cause resource
leak or undeterminable side effect when a thread is cancelled. However, this
is no longer true in new implementation.

In defering mode, a thread is canceled if cancellation request is pending and
later the thread enters a cancellation point, otherwise, a later
pthread_cancel() just causes SIGCANCEL to be sent to the target thread, and
causes target thread to abort system call, userland code in libthr then checks
cancellation state, and cancels the thread if needed. For example, the
cancellation point open(), the thread may be canceled at start,
but later, if it opened a file descriptor, it is not canceled, this avoids
file handle leak. Another example is read(), a thread may be canceled at start
of the function, but later, if it read some bytes from a socket, the thread
is not canceled, the caller then can decide if it should still enable cancelling
or disable it and continue reading data until it thinks it has read all
bytes of a packet, and keeps a protocol stream in health state, if user ignores
partly reading of a packet without disabling cancellation, then second iteration
of read loop cause the thread to be cancelled.
An exception is that the close() cancellation point always closes a file handle
despite whether the thread is cancelled or not.

The old mechanism is still kept, for a functions which is not so easily to
fix a cancellation problem, the rough mechanism is used.

Reviewed by: kib@

Use _SIG_VALID instead of expanded form of the macro.

Submitted by: Garrett Cooper <yanegomi gmail com>
MFC after: 1 week

Use UMTX_OP_WAIT_UINT_PRIVATE and UMTX_OP_WAKE_PRIVATE to save
time in kernel(avoid VM lookup).

- Copy signal mask out before THR_UNLOCK(), because THR_UNLOCK() may call
_thr_suspend_check() which messes sigmask saved in thread structure.
- Don't suspend a thread has force_exit set.
- In pthread_exit(), if there is a suspension flag set, wake up waiting-
thread after setting PS_DEAD, this causes waiting-thread to break loop
in suspend_common().

Increase and decrease in_sigcancel_handler accordingly to avoid possible
error caused by nested SIGCANCEL stack, it is a bit complex.

If a new thread is created, it inherits current thread's signal masks,
however if current thread is executing cancellation handler, signal
SIGCANCEL may have already been blocked, this is unexpected, unblock the
signal in new thread if this happens.

MFC after: 1 week

Add some function prototypes.

Remove umtx_t definition, use type long directly, add wrapper function
_thr_umtx_wait_uint() for umtx operation UMTX_OP_WAIT_UINT, use the
function in semaphore operations, this fixed compiler warnings.

test cancel_pending to save a thr_wake call in some specical cases.

Use kernel provided userspace condition variable to implement pthread
condition variable.

Eliminate atomic operations in thread cancellation functions, it should
reduce overheads of cancellation points.

Replace internal usage of struct umtx with umutex which can supports
real-time if we want, no functionality is changed.

1. Don't override underscore version of aio_suspend(), system(),
wait(), waitpid() and usleep(), they are internal versions and
should not be cancellation points.
2. Make wait3() as a cancellation point.
3. Move raise() and pause() into file thr_sig.c.
4. Add functions _sigsuspend, _sigwait, _sigtimedwait and _sigwaitinfo,
remove SIGCANCEL bit in wait-set for those functions, the signal is
used internally to implement thread cancellation.

WARNS level 4 cleanup.

Check cancellation state carefully to see we really need to call
_pthread_testcancel(). Preserve errno in _thr_suspend_check().

Add locking support for rtld.

Refine thread suspension code, now thread suspension is a blockable
operation, the caller is blocked util target threads are really
suspended, also avoid suspending a thread when it is holding a
critical lock.
Fix a bug in _thr_ref_delete which tests a never set flag.

Update copyright.

Import my recent 1:1 threading working. some features improved includes:
1. fast simple type mutex.
2. __thread tls works.
3. asynchronous cancellation works ( using signal ).
4. thread synchronization is fully based on umtx, mainly, condition
variable and other synchronization objects were rewritten by using
umtx directly. those objects can be shared between processes via
shared memory, it has to change ABI which does not happen yet.
5. default stack size is increased to 1M on 32 bits platform, 2M for
64 bits platform.
As the result, some mysql super-smack benchmarks show performance is
improved massivly.

Okayed by: jeff, mtm, rwatson, scottl

Make libthr async-signal-safe without costly signal masking. The guidlines I
followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate,
pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of
the rest of the pthread api is required to be async-signal-safe. This means
that only the three mentioned functions are safe to use from inside
signal handlers.
However, there are certain system/libc calls that are
cancellation points that a caller may call from within a signal handler,
and since they are cancellation points calls have to be made into libthr
to test for cancellation and exit the thread if necessary. So, the
cancellation test and thread exit code paths must be async-signal-safe
as well. A summary of the changes follows:

o Almost all of the code paths that masked signals, as well as locking the
pthread structure now lock only the pthread structure.
o Signals are masked (and left that way) as soon as a thread enters
pthread_exit().
o The active and dead threads locks now explicitly require that signals
are masked.
o Access to the isdead field of the pthread structure is protected by both
the active and dead list locks for writing. Either one is sufficient for
reading.
o The thread state and type fields have been combined into one three-state
switch to make it easier to read without requiring a lock. It doesn't need
a lock for writing (and therefore for reading either) because only the
current thread can write to it and it is an integer value.
o The thread state field of the pthread structure has been eliminated. It
was an unnecessary field that mostly duplicated the flags field, but
required additional locking that would make a lot more code paths require
signal masking. Any truly unique values (such as PS_DEAD) have been
reborn as separate members of the pthread structure.
o Since the mutex and condvar pthread functions are not async-signal-safe
there is no need to muck about with the wait queues when handling
a signal ...
o ... which also removes the need for wrapping signal handlers and sigaction(2).
o The condvar and mutex async-cancellation code had to be revised as a result
of some of these changes, which resulted in semi-unrelated changes which
would have been difficult to work on as a separate commit, so they are
included as well.

The only part of the changes I am worried about is related to locking for
the pthread joining fields. But, I will take a closer look at them once this
mega-patch is committed.

Make the minimum implementation of pthread_kill conform to the
functionality spelled out in SUSv3.
o Signal of 0 means do everything except send the signal
o Check that the signal is not invalid
o Check that the target thread is not dead/invalid

o Since we're not using signals for thread synchronization anymore,
sigprocmask no longer needs to be wrapped.
o raise(3) is applied to the calling thread in a threaded program.
o In the sigaction wrapper reference the correct structure.
o Don't treat SIGTHR especially anymore (infact it won't exist in
a little while).

Implement PThreads barriers and barrier attributes.

Don't wake up the thread after the signal handler
has been executed. On return from the signal handler
the call will either be restarted or EINTR will be returned,
but it will not go back to its previous state. So, it is
sufficient to simply change the state to 'running' without
actually trying to wake up the thread.

Fix the wrapper function around signals so that a signal handling
thread on one of the mutex or condition variable queues is removed
from those queues before the real signal handler is called.

Make WARNS2 clean. The fixes mostly included:
o removed unused variables
o explicit inclusion of header files
o prototypes for externally defined functions

Approved by: re/blanket libthr

Forced commit for previous revision

Correct reversed variable assignments.
Re-enable the call to _mutex_lock_backout(). This might
need revisiting once internal locking of mutex and cv is done.

Approved by: markm/mentor, re/blanket libthr
Reviewed by: jeff

msg2

o Correct a debug message that refered to the wrong function
o Remove an unncecesary if clause

Approved by: markm (mentor)(implicit)
Reviewd by: jeff

- Define curthread as _get_curthread() and remove all direct calls to
_get_curthread(). This is similar to the kernel's curthread. Doing
this saves stack overhead and is more convenient to the programmer.
- Pass the pointer to the newly created thread to _thread_init().
- Remove _get_curthread_slow().

- Add libthr but don't hook it up to the regular build yet. This is an
adaptation of libc_r for the thr system call interface. This is beta
quality code.