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

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?


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