Previously, the implementation of google::GetStackTrace() that uses
libunwind uses a global variable that enforces that only one thread may
invoke libunwind at a time. However, libunwind is thread-safe. The
comment above the variable indicates that it is to protect against
reentrancy issues.
Instead of using a global variable, it would be much better to use a
thread-local variable to protect against these reentrancy issues. That
should provide the needed reentrancy protection while allowing multiple
threads to get stack traces at the same time.
It also allows for the removal of the atomic CAS operations on the
variable.
Resolves#160.
Since we introduced the API to set signal handler and print a
stacktrace, we should avoid glibc's backtrace, which may call malloc.
Basically, we choose the way to produce a stacktrace as same as
perftools.
Also, I removed GetStackFrames, which is not used and not implemented
with glibc.
git-svn-id: https://google-glog.googlecode.com/svn/trunk@16 eb4d4688-79bd-11dd-afb4-1d65580434c0
