[tsan] Fix nested signal handling (#138599)

This PR fixes the bug reported in #134358.

In the current implementation of the tsan posix interceptors, the signal
set does not get restored to the correct original set, if a signal
handler gets called, while already inside of a signal handler. This
leads to the wrong signal set being set for the thread in which the
signal handler was called.

To fix this I introduced a stack of `__sanitizer_sigset_t` to keep all
the correct old signal sets and restore them in the correct order.

There was also already an existing test that tested nested / recursive
signal handlers, but it was disabled.
I therefore reenabled it, made it more robust by waiting for the second
thread to have been properly started and added checks for the signal
sets.
This test then failed before the introduction of the interceptor fix and
didn't fail with the fix.

@dvyukov What are your thoughts?

0 files changed, 0 insertions, 0 deletions