Re: [Xen-devel] [PATCH v3 5/5] xen: modify several static locks to unique names

[Juergen Gross <jgross@xxxxxxxx>]

On 04.09.19 10:58, Andrew Cooper wrote:
> On 04/09/2019 09:40, Jan Beulich wrote:
> > On 04.09.2019 10:25, Juergen Gross wrote:
> > > On 03.09.19 17:09, Jan Beulich wrote:
> > > > On 03.09.2019 17:03, Juergen Gross wrote:
> > > > > On 03.09.19 16:53, Jan Beulich wrote:
> > > > > > On 29.08.2019 12:18, Juergen Gross wrote:
> > > > > > > In order to have unique names when doing lock profiling several local
> > > > > > > locks "lock" need to be renamed.
> > > > > > But these are all named simply "lock" for a good reason, including
> > > > > > because they're all function scope symbols (and typically the
> > > > > > functions are all sufficiently short). The issue stems from the
> > > > > > dual use of "name" in
> > > > > >
> > > > > > #define _LOCK_PROFILE(name) { 0, #name, &name, 0, 0, 0, 0, 0 }
> > > > > >
> > > > > > so I'd rather suggest making this a derivation of a new
> > > > > >
> > > > > > #define _LOCK_PROFILE_NAME(lock, name) { 0, #name, &lock, 0, 0, 0, 0, 0 }
> > > > > >
> > > > > > if there's no other (transparent) way of disambiguating the names.
> > > > > This will require to use a different DEFINE_SPINLOCK() variant, so e.g.
> > > > > DEFINE_SPINLOCK_LOCAL(), which will then include the needed "static" and
> > > > > add "@<func>" to the lock profiling name. Is this okay?
> > > > To be frank - not really. I dislike both, and would hence prefer to
> > > > stick to what there is currently, until someone invents a transparent
> > > > way to disambiguate these. I'm sorry for being unhelpful here.
> > > I think I have found a way: I could add __FILE__ and __LINE__ data to
> > > struct lock_profile. In lock_prof_init() I could look for non-unique
> > > lock names and mark those to be printed with the __FILE__ and __LINE__
> > > data added to the names.
> > >
> > > Would you be fine with this approach?
> > I would be, but I'm afraid Andrew won't (as with any new uses of __LINE__).
> The ok-ness of using __LINE__ is inversely proportional to the
> likelihood of developing a livepatch for this particular build of Xen,
> and what additional patching delta it would cause through unrelated changes.
Not related to this patch, but to __LINE__ and livepatching: have you
considered to use the "#line" directive to avoid unrelated diffs?


Juergen

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