Messages in this thread | | | Date | Wed, 8 Feb 2012 16:42:54 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH] ptrace: add ability to get clear_tid_address |
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On Wed, Feb 08, 2012 at 12:30:47PM +0000, Pedro Alves wrote: > > > > Yes, could be, but it means you have to install pthread debug libs, right? > > (have no idea actually since I personally use debug printing instead of > > breakpoints). > > Not really more than what we need today. Just some exported function name > in the elf symbol tables. Assuming a the program is using clear_child_tid > address for pthread_join as glibc is may not be a good idea. It's doing > things at the wrong layer. Also, hardware watchpoints are a scarse > resource.
It's pretty precious resource still incredibly useful. ok, i see what you mean, thanks.
> > >> It's the kernel that writes to this address, so I've no > >> idea if the watchpoint trap ends up visible on userspace. Which thread > >> would it be reported to, given that this is cleared when the child > >> is gone, I have no idea either. > > > > Yeah, need some help from someone who wrote hw-breakpoints support in > > kernel (i don't remember the details). > > 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. >
Thanks for info.
Cyrill
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