libpthread: New pthread__smt_wait to put CPU in low power for spin.

This is now distinct from pthread__smt_pause, which is for spin lock
backoff with no paired wakeup.

On Arm, there is a single-bit event register per CPU, and there are two
instructions to manage it:

- wfe, wait for event -- if event register is clear, enter low power
mode and wait until event register is set; then exit low power mode
and clear event register

- sev, signal event -- sets event register on all CPUs (other
circumstances like interrupts also set the event register and cause
wfe to wake)

These can be used to reduce the power consumption of spinning for a
lock, but only if they are actually paired -- if there's no sev, wfe
might hang indefinitely. Currently only pthread_spin(3) actually
pairs them; the other lock primitives (internal lock, mutex, rwlock)
do not -- they have spin lock backoff loops, but no corresponding
wakeup to cancel a wfe.

It may be worthwhile to teach the other lock primitives to pair
wfe/sev, but that requires some performance measurement to verify
it's actually worthwhile. So for now, we just make sure not to use
wfe when there's no sev, and keep everything else the same -- this
should fix severe performance degredation in libpthread on Arm
without hurting anything else.

No change in the generated code on amd64 and i386. No change in the
generated code for pthread_spin.c on arm and aarch64 -- changes only
the generated code for pthread_lock.c, pthread_mutex.c, and
pthread_rwlock.c, as intended.

PR port-arm/57437

XXX pullup-10

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.)

Retire ifdef ERRORCHECK in pthread(3)

It is enabled unconditionally since 2003 and used only for rwlocks and
spinlocks.

LLVM sanitizers make assumptions that these checks are enabled always.

Refactor libpthread checks for invalid arguments

Switch from manual functions to pthread__error().

branches: 1.6.32;
Add a pthread__smt_wake and add support for it on arm along with
pthread__smt_pause. These are implemented using the ARM instructions
SEV (wake) and WFE (pause). These are treated as NOPs on ARM CPUs that
don't support them.

branches: 1.5.4; 1.5.8;
Remove clause 3 and 4 from TNF licenses

branches: 1.4.4;
machine/lock.h, not sys/lock.h

For PR bin/37347:

- Override __libc_thr_init() instead of using our own constructor.
- Add pthread__getenv() and use instead of getenv(). This is used before
we are up and running and unfortunatley getenv() takes locks.

Other changes:

- Cache the spinlock vectors in pthread__st. Internal spinlock operations
now take 1 function call instead of 3 (i386).
- Use pthread__self() internally, not pthread_self().
- Use __attribute__ ((visibility("hidden"))) in some places.
- Kill PTHREAD_MAIN_DEBUG.

Merge nick-csl-alignment.

branches: 1.1.2; 1.1.4;
Trim fat off libpthread internal spinlock operations. Makes a mesurable
improvement across the board.

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.)

Retire ifdef ERRORCHECK in pthread(3)

It is enabled unconditionally since 2003 and used only for rwlocks and
spinlocks.

LLVM sanitizers make assumptions that these checks are enabled always.

Refactor libpthread checks for invalid arguments

Switch from manual functions to pthread__error().

branches: 1.6.32;
Add a pthread__smt_wake and add support for it on arm along with
pthread__smt_pause. These are implemented using the ARM instructions
SEV (wake) and WFE (pause). These are treated as NOPs on ARM CPUs that
don't support them.

branches: 1.5.4; 1.5.8;
Remove clause 3 and 4 from TNF licenses

branches: 1.4.4;
machine/lock.h, not sys/lock.h

For PR bin/37347:

- Override __libc_thr_init() instead of using our own constructor.
- Add pthread__getenv() and use instead of getenv(). This is used before
we are up and running and unfortunatley getenv() takes locks.

Other changes:

- Cache the spinlock vectors in pthread__st. Internal spinlock operations
now take 1 function call instead of 3 (i386).
- Use pthread__self() internally, not pthread_self().
- Use __attribute__ ((visibility("hidden"))) in some places.
- Kill PTHREAD_MAIN_DEBUG.

Merge nick-csl-alignment.

branches: 1.1.2; 1.1.4;
Trim fat off libpthread internal spinlock operations. Makes a mesurable
improvement across the board.

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.)

Retire ifdef ERRORCHECK in pthread(3)

It is enabled unconditionally since 2003 and used only for rwlocks and
spinlocks.

LLVM sanitizers make assumptions that these checks are enabled always.

Refactor libpthread checks for invalid arguments

Switch from manual functions to pthread__error().

branches: 1.6.32;
Add a pthread__smt_wake and add support for it on arm along with
pthread__smt_pause. These are implemented using the ARM instructions
SEV (wake) and WFE (pause). These are treated as NOPs on ARM CPUs that
don't support them.

branches: 1.5.4; 1.5.8;
Remove clause 3 and 4 from TNF licenses

branches: 1.4.4;
machine/lock.h, not sys/lock.h

For PR bin/37347:

- Override __libc_thr_init() instead of using our own constructor.
- Add pthread__getenv() and use instead of getenv(). This is used before
we are up and running and unfortunatley getenv() takes locks.

Other changes:

- Cache the spinlock vectors in pthread__st. Internal spinlock operations
now take 1 function call instead of 3 (i386).
- Use pthread__self() internally, not pthread_self().
- Use __attribute__ ((visibility("hidden"))) in some places.
- Kill PTHREAD_MAIN_DEBUG.

Merge nick-csl-alignment.

branches: 1.1.2; 1.1.4;
Trim fat off libpthread internal spinlock operations. Makes a mesurable
improvement across the board.

Retire ifdef ERRORCHECK in pthread(3)

It is enabled unconditionally since 2003 and used only for rwlocks and
spinlocks.

LLVM sanitizers make assumptions that these checks are enabled always.

Refactor libpthread checks for invalid arguments

Switch from manual functions to pthread__error().

Add a pthread__smt_wake and add support for it on arm along with
pthread__smt_pause. These are implemented using the ARM instructions
SEV (wake) and WFE (pause). These are treated as NOPs on ARM CPUs that
don't support them.

branches: 1.5.4; 1.5.8;
Remove clause 3 and 4 from TNF licenses

branches: 1.4.4;
machine/lock.h, not sys/lock.h

For PR bin/37347:

- Override __libc_thr_init() instead of using our own constructor.
- Add pthread__getenv() and use instead of getenv(). This is used before
we are up and running and unfortunatley getenv() takes locks.

Other changes:

- Cache the spinlock vectors in pthread__st. Internal spinlock operations
now take 1 function call instead of 3 (i386).
- Use pthread__self() internally, not pthread_self().
- Use __attribute__ ((visibility("hidden"))) in some places.
- Kill PTHREAD_MAIN_DEBUG.

Merge nick-csl-alignment.

branches: 1.1.2; 1.1.4;
Trim fat off libpthread internal spinlock operations. Makes a mesurable
improvement across the board.

Refactor libpthread checks for invalid arguments

Switch from manual functions to pthread__error().

Add a pthread__smt_wake and add support for it on arm along with
pthread__smt_pause. These are implemented using the ARM instructions
SEV (wake) and WFE (pause). These are treated as NOPs on ARM CPUs that
don't support them.

branches: 1.5.4; 1.5.8;
Remove clause 3 and 4 from TNF licenses

branches: 1.4.4;
machine/lock.h, not sys/lock.h

For PR bin/37347:

- Override __libc_thr_init() instead of using our own constructor.
- Add pthread__getenv() and use instead of getenv(). This is used before
we are up and running and unfortunatley getenv() takes locks.

Other changes:

- Cache the spinlock vectors in pthread__st. Internal spinlock operations
now take 1 function call instead of 3 (i386).
- Use pthread__self() internally, not pthread_self().
- Use __attribute__ ((visibility("hidden"))) in some places.
- Kill PTHREAD_MAIN_DEBUG.

Merge nick-csl-alignment.

branches: 1.1.2; 1.1.4;
Trim fat off libpthread internal spinlock operations. Makes a mesurable
improvement across the board.