Messages in this thread |  | | | From | David Mosberger <> | | Date | Wed, 11 May 2005 01:55:14 -0700 | | Subject | Re: [patch] add arch_ptrace_stop() hook and use it on ia64 |
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>>>>> On Tue, 10 May 2005 17:59:46 -0700, Roland McGrath <roland@redhat.com> said:
Roland> (This leads to threads in TASK_TRACED with a pending Roland> SIGKILL, that cannot be killed with repeated kill -9s, and Roland> live until the tracer uses PTRACE_CONT, detaches, or dies.)
Ah, yes, I see now that SIGKILL is a rather nasty special-case.
Roland> When I suggested this change for ia64 originally, I Roland> overlooked the need to handle blocking in writing to user Roland> memory. I'd like to give a little more thought to the Roland> general case. As long as only uninterruptible waits are Roland> provoked by an arch hook, then I think it is reasonably Roland> solvable. I think that SIGKILL races are the only ones that Roland> can arise, and those can be addressed with some signal Roland> bookkeeping changes. I'd like to give it a little more Roland> thought. I expect it will wind up being some core changes Roland> that make it safe for an arch hook to drop and reacquire the Roland> siglock if it's doing something that won't always complete Roland> quickly, and then this will all happen before changing Roland> state, unlocking, and deciding to block (which won't be done Roland> if there was an intervening SIGKILL).
OK, that sounds good to me. Please keep me posted. It would be nice to have this hook in place, since it does fix a bug on ia64 and makes the code simpler.
Thanks,
--david
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