On Wed, Aug 19, 2020 at 05:14:18PM -0700, Andy Lutomirski wrote: > On Wed, Aug 19, 2020 at 3:47 PM Josh Poimboeuf <jpoim...@redhat.com> wrote: > > What amazes me is that it successfully schedules back to the end of the > > #DB handler finish and everything keeps working. > > > > Do we not have assertions in the scheduler to catch this? > > You almost nailed it. > > I'm pretty sure you have the buggy sequence of events right, but for > the wrong reason. There's nothing wrong with scheduling when > delivering SIGTRAP, but it's definitely wrong to blindly save and > restore DR7 around scheduling and around ptrace invocations. Remember > this is an entry from user mode, so it runs on the user stack.
Wow, I had no idea user #DB's run on the task stack. The scheduling from #DB blew my mind :-) What's the purpose of that? -- Josh
