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SubjectRe: [patch] add arch_ptrace_stop() hook and use it on ia64
>>>>> 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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