On 10/06, Srikar Dronamraju wrote:
>
> * Oleg Nesterov <o...@redhat.com> [2012-09-30 21:42:11]:
>
> > @@ -1391,6 +1392,16 @@ static struct uprobe *find_active_uprobe(unsigned
> > long bp_vaddr, int *is_swbp)
> > if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
> > mmf_recalc_uprobes(mm);
> > up_read(&mm->mmap_sem);
> > + /*
> > + * TODO: move copy_insn/etc into _register and remove this hack.
> > + * After we hit the bp, _unregister + _register can install the
> > + * new and not-yet-analyzed uprobe at the same address, restart.
> > + */
> > + smp_rmb(); /* pairs with wmb() in install_breakpoint() */
> > + if (uprobe && unlikely(!(uprobe->flags & UPROBE_COPY_INSN))) {
> > + uprobe = NULL;
> > + *is_swbp = 0;
> > + }
> >
> > return uprobe;
> > }
>
> Should we be adding this check handle_swbp() around can_skip_step()?
>
> The earliest we access arch.insn is in can_skip_step. So we give some
> more time for the instruction to be copied.
handle_swbp:
if (can_skip_sstep(uprobe, regs))
goto out;
but if we hit a non-UPROBE_COPY_INSN uprobe, we need "goto restart".
> Also it will probably be a little cleaner, (Not having to drop a uprobe
> reference, not having to reset is_swbp.)
We can change handler_chain() (which also checks UPROBE_RUN_HANDLER)
to return "bool restart", not sure this will be more clean.
And if we change handler_chain(), I think it should return bitmask,
for (uc = uprobe->consumers; uc; uc = uc->next)
ret |= uc->handler(...);
return ret;
for the future changes... (say, we can remove bp if consumers do not
want to trace this task). Not sure it makes sense to change it right
now.
So. Should I leave this patch as is? Or do you want me to move this
check into handler_chain() and make it return "bool restart"?
Oleg.
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