Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

MFC r318539 r318580 r318581 r318584 r318749 r318952 r318953 r318955

libthr: fix warnings at WARNS=6

Fix warnings about the following when WARNS=6 (which I will commit soon):

- casting away const
- no previous 'extern' declaration for non-static variable
- others as explained by #pragmas and comments
- unused parameters

libthr: disable thread-safety warnings

These warnings don't make sense for code that implements
the locking primitives.

libthr: change CHECK_AND_INIT_RWLOCK to an inline function

This was prompted by a compiler warning about 'ret' shadowing
a local variable in the callers of the macro.

libthr: Use CLI flags instead of pragmas to disable warnings

People tweaking the build system or compilers tend to look into
the Makefile and not into the source. Having some warning controls
in the Makefile and some in the source code is surprising.

Pragmas have the advantage that they leave the warnings enabled
for more code, but that advantage isn't very relevant in these cases.

libthr: fix warnings from GCC when WARNS=6

Fix warnings about:
- redundant declarations
- a local variable shadowing a global function (dlinfo)
- an old-style function definition (with an empty parameter list)
- a variable that is possibly used uninitialized

libthr: prevent setcontext() from masking SIGTHR

__thr_setcontext() mistakenly tested for the presence of SIGCANCEL
in its local ucontext_t instead of the parameter. Therefore,
if a thread calls setcontext() with a context whose signal mask
contains SIGTHR (a.k.a. SIGCANCEL), that signal will be blocked,
preventing the thread from being cancelled or suspended.

Sponsored by: Dell EMC

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Use __FBSDID() for .c files from lib/libthr/thread.

Sponsored by: The FreeBSD Foundation

Some third-party malloc(3) implementations use pthread_setspecific(3)
to handle per-thread information. Since our pthread_setspecific()
implementation calls calloc(3) to allocate per-thread specific data
storage, things get complicated.

Switch the allocator to use bare mmap(2). There is some loss of the
allocated page, since e.g. on amd64, PTHREAD_KEYS_MAX * sizeof(struct
pthread_specific_elem) is 3K (it actually spans whole page due to
padding), but I believe it is more acceptable than additional code for
specialized allocator().

The alternatives would either to make the specific data array be part of
the struct thread, or use internal bindings to call the libc malloc,
avoiding interposing.

Also do the style pass over the thr_spec.c, esp. simplify the
conditionals nesting by returning early when an error detected.
Remove trivial comments.

Found by: yuri@rawbw.com
PR: 200138
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks

Return one-based key so that user can check if the key is ever allocated
in the first place.

Initial patch submitted by: phk

Unregister thread specific data destructor when a corresponding dso
is unloaded.

don't report error if key was deleted.

PR: threads/135462

In _pthread_key_create() ensure that libthr is initialized. This
fixes a NULL-dereference of curthread when libstdc+ initializes
the exception handling globals on archs we can't use GNU TLS due
to lack of support in binutils 2.15 (i.e. arm and sparc64), yet,
thus making threaded C++ programs compiled with GCC 4.2.1 work
again on these archs.

Reviewed by: davidxu
MFC after: 3 days

Remove 3rd clause, renumber, ok per email

Explicitly request pre-zeroed memory instead of memset'ing our
own.

Ok'ed by: davidxu

WARNS level 4 cleanup.

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

- 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.