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SubjectRe: [PATCH v8 3.2.0-rc5 1/9] uprobes: Install and remove breakpoints.
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On Wed, 2012-01-04 at 17:51 +0100, Peter Zijlstra wrote:

> > + if (is_register)
> > + ret = install_breakpoint(mm, uprobe, vma, vi->vaddr);
> > + else
> > + remove_breakpoint(mm, uprobe, vi->vaddr);
> > +
> > + up_read(&mm->mmap_sem);
> > + mmput(mm);
> > + if (is_register) {
> > + if (ret && ret == -EEXIST)
> > + ret = 0;
> > + if (ret)
> > + break;
> > + }
>
> Since you init ret := 0 and remove_breakpoint doesn't change it, this
> conditional on is_register is superfluous.

True, but I would argue that this is easier to understand. That is, we
only break on a failed install_breakpoint (is_register is set). If I
looked at this code and saw:

if (is_register)
ret = install_breakpoint()
else
remove_breakpoint()
[...]

if (ret && ret == -EEXIST)
ret = 0;
if (ret)
break;
I would first think that there might be a bug. That is, we should have a
ret = remove_breakpoint().

Thus, I would say, either leave this as is and hope gcc is smart enough
to optimize out the if (is_register), or add the comment:
/* ret will always be zero on remove_breakpoint */
if (ret && ret == -EEXIST)
ret = 0;
if (ret)
break;
-- Steve

>
> > + }
> > + list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) {
> > + list_del(&vi->probe_list);
> > + kfree(vi);
> > + }
> > + return ret;
> > +}




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