Messages in this thread | | | Date | Mon, 16 Apr 2012 01:44:01 +0200 | From | Oleg Nesterov <> | Subject | Re: [RFC 0/6] uprobes: kill uprobes_srcu/uprobe_srcu_id |
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I'll write another email tomorrow, just one note...
On 04/15, Peter Zijlstra wrote: > > OK, still not seeing how your proposal could work.. consider the below > patch comment, I'm not seeing how is_swbp_at_addr_fast() deals with an > in-progress INT3 while we remove the probe. > > By ensuring the non-race with reg/unreg it will either find the uprobe > (no problem)
Yes,
> or not find it and not see a breakpoint instruction either, > even though the pending breakpoint was generated by a uprobe (which is > now gone),
Yes,
> causing a false positive SIGTRAP.
No. Please note that if is_swbp_at_addr_fast() sets is_swbp == 0 we restart this insn.
(note that we also restart if get_user_pages() fails, this is hopefully is more correct too but minor).
> Or am I still not getting it?
My experience shows this is very unlikely. I am starting to think I missed something, will re-check.
And. I have another reason for down_write() in register/unregister. I am still not sure this is possible (I had no time to try to implement), but it seems to me we can kill the uprobe counter in mm_struct.
Oleg.
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