Messages in this thread | | | Date | Wed, 08 Feb 2012 18:04:20 +0000 | From | Pedro Alves <> | Subject | Re: [PATCH] ptrace: add ability to get clear_tid_address |
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On 02/08/2012 05:31 PM, Oleg Nesterov wrote: > On 02/08, Pedro Alves wrote: >> >> I just tried it. This is &pthread->tid in glibc/libpthread, so with debug >> info it's easy to figure out where to set the watchpoint manually with gdb >> without asking the kernel. Doesn't work. ptrace doesn't show any trap >> for the kernel writes. > > The tracee simply can't report this trap. it is already dead ;) and > hw breakpoint (used by ptrace) is "pinned" to the thread.
Right, as I said. :-) I saw that a watchpoint trap isn't reported either for the CLONE_CHILD_SETTID case (that is, within clone, when the kernel writes the tid to the memory address passed in to the clone syscall). I wouldn't have been surprised to see the trap in userspace in either the parent or the child, though I'm not really surprised to not see it either.
-- Pedro Alves
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