In c-archive mode, when we turn off profiling, we restore the
previous handler for SIGPROF, and ignore SIGPROF signals if no
handler was installed. So if a pending signal lands after we
remove the Go signal handler, it will not kill the program.
In the current code there is a small window, where we can still
receive signals but we are set to not handling the signal. If a
signal lands in this window (possibly on another thread), it will
see that we are not handling this signal and no previous handler
installed, and kill the program. To avoid this race, we set the
previous handler to SIG_IGN (ignoring the signal) when turning on
profiling. So when turning off profiling we'll ignore the signal
even if a stray signal lands in the small window.
Fixes #43828.
Change-Id: I304bc85a93ca0e63b0c0d8e902b097bfdc8e3f1d
Reviewed-on: https://go-review.googlesource.com/c/go/+/374074
Trust: Cherry Mui <cherryyz@google.com> Reviewed-by: Ian Lance Taylor <iant@golang.org>