Bug 236035

When tracing a process using ptrace and there are multiple threads in the tracing process hitting the same breakpoint, sometimes main thread exits (WIFEXITED(status) is TRUE) before last queued TRAP_BKPT signal(s) have been delivered to the tracing process. So a final breakpoint hits counter is less than it should be.

Steps to reproduce:

cd /tmp
git clone https://github.com/rayrapetyan/ptrace_bug_poc.git
cd ptrace_bug_poc
mkdir build
cd build
cmake ..
make

Run ~20 times:

/tmp/ptrace_bug_poc/build/src/ptrace_test/ptrace_test /tmp/ptrace_bug_poc/build/src/mt_example/mt_example 0x201385

-------
Note: make sure 0x201385 is a call to <printf@plt> in "/tmp/ptrace_bug_poc/build/src/mt_example/mt_example":
gdb /tmp/ptrace_bug_poc/build/src/mt_example/mt_example
disassemble foo
-------

Wait fo appearance of:
"BOOM! Invalid BP hits counter (hits: 1, tid: XXXX)"
at the end of the output (most of the times it will be "SUCCESS")