Description: add areas of missing coverage across the core codebase.
Risk Level: low
Testing: adds more testing!

Signed-off-by: Jose Nino <jnino@lyft.com>
Signed-off-by: JP Simard <jp@jpsim.com>

Description: add areas of missing coverage across the core codebase.
Risk Level: low
Testing: adds more testing!

Signed-off-by: Jose Nino <jnino@lyft.com>
Signed-off-by: JP Simard <jp@jpsim.com>

Our perftools_pthread_once implementation has some ifdefs and what
not. I.e. some OSes have complications around early usage and windows
is windows. But in fact we can implement trivial spinlock-supported
implementation and depend on nothing.

Update issue envoyproxy#1110

This facility allowed us to build tcmalloc without linking in actual
-lpthread. Via weak symbols we checked at runtime if pthread functions
are available and if not, special single-threaded stubs were used
instead. Not always brining in pthread dependency helped performance
of some programs or libraries which depended at runtime on whether
threads are linked or not. Most notable of those are libstdc++ which
uses non-atomic refcounting on single threaded programs.

But such optional dependency on pthreads caused complications for
nearly no benefit. One trouble was reported in github issue envoyproxy#1110.

This days glibc/libstdc++ combo actually depends on
sys/single_threaded.h facility. So bringing pthread at runtime is
fine. Also modern glibc ships pthread symbols inside libc anyways and
libpthread is empty. I also found that for whatever reason on BSDs and
osx we already pulled in proper pthreads too.

So we loose nothing and we get issue envoyproxy#1110 fixed. And we simplify
everything.