Blacklist the "threaded-ml" thread, which seems to mask the
backtrace signal.
Improve signal-handler synchronozation, to avoid segfaulting when
giving up on waiting for all threads to handle the signal.
Furthermore, when one or more threads fail to handle the signal in
time, return a GimpBacktrace instance with backtraces for all the
other threads, and with empty backtraces for all the non-responding
threads, instead of returning NULL and leaking the allocated
instance. Don't blacklist threads that failed to handle the signal
in time, and instead shorten the wait period for handling the
signal, and yield execution during waiting to lower the CPU usage.
In the GimpBacktrace Linux backend, always use libunwind, when
available, to find symbol names, even if dladdr() or libbacktrace
had already found one. libunwind provides more descriptive names
in certain cases, and, in particular, full symbol names for C++
lambdas.
Note that, in some cases, this can result in a discrepancy between
the reported symbol name, and the corresponding source location.
Improve out-of-range check in gimp_backtrace_find_thread_by_id().
Remove unnecessary #include <exchndl.h> in gimpbacktrace-windows.c,
and revert commit 644234e99d (the
DrMingw detection happens at runtime). The Windows backend can
work without DrMingw, it just can't find all the symbols, and
doesn't provide source-location information.
The "running" attribute (readable through
gimp_backtrace_is_thread_running(), and recorded in the performance
log) specifies if the thread was in a running or suspended state at
the time the backtrace was taken. It is accurate on Linux, but
only approximated on Windows.
Adapt the performance-log-expand.py tool to maintain this attribute
(and any future thread attributes we might add).
Add source filename and line number fields to the
GimpBacktraceAddressInfo struct, populated through
gimp_backtrace_get_address_info(). This is not currently supported
by the Linux backend, but is supported by the Windows backend,
which we'll be added in the next commit.
This function returns information about the given address, which
is currently mostly limited to the corresponding symbol
information, but we might want to add address-specific information
in the future, such as a line number.
GimpBacktrace provides an interface for creating and traversing
multi-threaded backtraces, as well as querying symbol information.
While we already have some backtrace functionality, it relies on
external tools for the most part, and as such is rather expensive,
and is only meant for producing opaque backtraces. GimpBacktrace,
on the other hand, is meant to be relatively cheap (we're going to
use it for profiling,) and allow inspection of the backtrace data.
In the future, it might make sense to replace some, or all, of the
other backtrace functions with GimpBacktrace.
GimpBacktrace currently only supports Linux. By default, it uses
dladdr() to query symbol information, which is somewhat limited (in
particular, it doesn't work for static functions.) When libunwind
is installed, GimpBacktrace uses it to get more complete symbol
information. libunwind is currently an optional dependency, but it
might make sense to promote it to a mandatory, or opt-out,
dependency, as it's lightweight and widely available.
On other platforms, the GimpBacktrace interface can still be used,
but it always returns NULL backtraces.
