pthread: Nix trailing whitespace.

libpthread: Move namespacing include to top of .c files.

Stuff like libc's namespace.h, or atomic_op_namespace.h, which does
namespacing tricks like `#define atomic_cas_uint _atomic_cas_uint',
has to go at the top of each .c file. If it goes in the middle, it
might be too late to affect the declarations, and result in compile
errors.

I tripped over this by including <sys/atomic.h> in mips
<machine/lock.h>.

(Maybe we should create a new pthread_namespace.h file for the
purpose, but this'll do for now.)

- Allow libpthread to be dlopened again, by providing libc stubs to libpthread.
- Fail if the dlopened libpthread does pthread_create(). From manu@
- Discussed at length in the mailing lists; approved by core@
- This was chosen as the least intrusive patch that will provide
the necessary functionality.
XXX: pullup to 6

add assertions

Replace the simple implementation of pthread_key_{create,destroy}
and pthread_{g,s}etspecific functions, to one that invalidates
values of keys in other threads when pthread_key_delete() is called.
This fixes chromium, which expects pthread_key_delete() to do
cleanup in all threads.

Only copy the ucontext_t in pthread_setcontext if _UC_TLSBASE is set.
Conditionalize the test on _UC_TLSBASE being defined.

branches: 1.22.2;
setcontext() used to be incompatible with -lpthread since it affected
the TLS pointer, therefore wrecking the pthread environement.

Some ports had _UC_TLSBASE flag or equivalent (_UC_UNIQUE on alpha)
that controlled whether setcontext() would change the TLS pointer.
This change let libpthread override setcontext() with its own version
that unsets _UC_TLSBASE, enabling safe usage of setcontext() with
-lpthread.

We also have the following required changes here:
- rename alpha's _UC_UNIQUE into _UC_TLSBASE
- add _UC_TLSBASE definition in header file for all ports
(powerpc, sh3, sparc and sparc64 lack the implementation for now)
- introduce a libc stub that can be overriden for setcontext()
- modify MD libcs swapcontext() implementations so that they use the
setcontext() libc stub instead of doing a plain system call.

While we are there:
- document various MD _UC_* flags in header file
- add libc and libpthread tests for swapcontext() behavior
(hopefully helpful to spot MD problems introduced with this change)

Future work:
- Deciding whether kernel support or _UC_TLSBASE should be added for
powerpc, sh3, sparc and sparc64 is left to portmasters
sparc64

Approved by core@

branches: 1.21.2; 1.21.6; 1.21.22;
pthread_curcpu_np: remove hack for pthread_dummy_lwpctl.

branches: 1.20.2;
Remove clause 3 and 4 from TNF licenses

branches: 1.19.2;
Back out previous. It seems to expose another bug in libpthread/libc,
potentially errno being used before threading is up and running.

Move pthread__errno() into pthread_specific.c so it gets the "no stack
frame" treatment.

cast -1 to unsigned int.

pthread_curcpu_np: map LWPCTL_CPU_NONE to 0 so that this works in the case
of _lwp_ctl failure.

Back out previous now that libc/libpthread are initialized first.

Hack around ld.so initializing pthread users before libpthread/libc.

Add thr_curcpu(), pthread_curcpu_np().

Cosmetic change.

branches: 1.11.2;
- Reinitialize the absolute minimum when recycling user thread state.
Chops another ~10% off create/join in a loop on i386.
- Disable low level debugging as this is stable. Improves benchmarks
across the board by a small percentage. Uncontested mutex acquire
and release in a loop becomes about 8% quicker.
- Minor cleanup.

branches: 1.10.20;
Split out pthread_{set,get}specific() into a separate file and arrange
for that file to not be built with profiling. This makes it reasonable to
use pthread_{set,get}specific() to implement thread-safe profiline call counts.

Don't use PTHREAD_DESTRUCTOR_ITERATIONS; the constant is going away.

Fix typo in comment.

Remove an unnecessary test in pthread_getspecific().

add __RCSID()

Remove unused #include <assert.h>

Don't bother acquiring the tsd_lock and reading the destructor function
if the corresponding TSD entry is empty.

Cuts down lock/unlock pairs for this operation from 256 to the number
of active TSD entries; sicne this is done when every thread exits, it saves
many total lock/unlock pairs.

de-lint

Merge the nathanw_sa branch.

branches: 1.1.2;
file pthread_specific.c was initially added on branch nathanw_sa.