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Re: [PATCH v3 1/6] xen: add reference counter support
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 16 Mar 2023 17:32:38 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Thu, 16 Mar 2023 16:32:50 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 16.03.2023 17:19, Roger Pau Monné wrote:
> On Tue, Mar 14, 2023 at 08:56:29PM +0000, Volodymyr Babchuk wrote:
>> +static inline void refcnt_get(refcnt_t *refcnt)
>> +{
>> + int old = atomic_add_unless(&refcnt->refcnt, 1, 0);
>
> Occurred to me while looking at the next patch:
>
> Don't you also need to print a warning (and saturate the counter
> maybe?) if old == 0, as that would imply the caller is attempting
> to take a reference of an object that should be destroyed? IOW: it
> would point to some kind of memory leak.
Hmm, I notice the function presently returns void. I think what to do
when the counter is zero needs leaving to the caller. See e.g.
get_page() which will simply indicate failure to the caller in case
the refcnt is zero. (There overflow handling also is left to the
caller ... All that matters is whether a ref can be acquired.)
Jan
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