How does gdb manage thread-specific breakpoints

Question

When gdb puts a breakpoint in a Target process, it replaces one instruction by int3. I am wondering how it works when this breakpoint should ne active for a specific thread...

Answer 1

Copying from this answer:

For a thread-specific breakpoint, the debugger inserts a process-wide breakpoint, then simply immediately resumes any thread which hits the breakpoint, unless the thread is the specific one that you wanted to stop.