On 2/19/24 08:12, Jan Beulich wrote:
> On 19.02.2024 13:47, Stewart Hildebrand wrote:
>> On 2/19/24 07:10, Jan Beulich wrote:
>>> On 19.02.2024 12:47, Stewart Hildebrand wrote:
>>>> @@ -895,6 +891,15 @@ int vpci_msix_arch_print(const struct vpci_msix *msix)
>>>> {
>>>> unsigned int i;
>>>>
>>>> + /*
>>>> + * Assert that d->pdev_list doesn't change.
>>>> ASSERT_PDEV_LIST_IS_READ_LOCKED
>>>> + * is not suitable here because it may allow either pcidevs_lock() or
>>>> + * d->pci_lock to be held, but here we rely on d->pci_lock being
>>>> held, not
>>>> + * pcidevs_lock().
>>>> + */
>>>> + ASSERT(rw_is_locked(&msix->pdev->domain->pci_lock));
>>>> + ASSERT(spin_is_locked(&msix->pdev->vpci->lock));
>>>
>>> There's no "d" in sight here, so it's a little odd that "d" is being talked
>>> about. But I guess people can infer what's meant without too much trouble.
>>
>> I can s/d->pci_lock/msix->pdev->domain->pci_lock/ for the next rev.
>
> Or simply drop the d-s? That would be better for readability's sake,
> I think.
OK
>>>> @@ -313,17 +316,36 @@ void vpci_dump_msi(void)
>>>> {
>>>> /*
>>>> * On error vpci_msix_arch_print will always return
>>>> without
>>>> - * holding the lock.
>>>> + * holding the locks.
>>>> */
>>>> printk("unable to print all MSI-X entries: %d\n", rc);
>>>> - process_pending_softirqs();
>>>> - continue;
>>>> + goto pdev_done;
>>>> }
>>>> }
>>>>
>>>> + /*
>>>> + * Unlock locks to process pending softirqs. This is
>>>> + * potentially unsafe, as d->pdev_list can be changed in
>>>> + * meantime.
>>>> + */
>>>> spin_unlock(&pdev->vpci->lock);
>>>> + read_unlock(&d->pci_lock);
>>>> + pdev_done:
>>>> process_pending_softirqs();
>>>> + if ( !read_trylock(&d->pci_lock) )
>>>> + {
>>>> + printk("unable to access other devices for the domain\n");
>>>> + goto domain_done;
>>>> + }
>>>> }
>>>> + read_unlock(&d->pci_lock);
>>>> + domain_done:
>>>> + /*
>>>> + * We need this label at the end of the loop, but some
>>>> + * compilers might not be happy about label at the end of the
>>>> + * compound statement so we adding an empty statement here.
>>>> + */
>>>> + ;
>>>
>>> As to "some compilers": Are there any which accept a label not followed
>>> by a statement? Depending on the answer, this comment may be viewed as
>>> superfluous. Or else I'd ask about wording: Besides a grammar issue I
>>> also don't view it as appropriate that a comment talks about "adding"
>>> something when its adjacent code that is meant. That something is there
>>> when the comment is there, hence respective wording should imo be used.
>>
>> It seems like hit or miss whether gcc would accept it or not (prior
>> discussion at [1]). I agree the comment is rather lengthy for what it's
>> trying to convey. I'd be happy to either remove the comment or reduce
>> it to:
>>
>> domain_done:
>> ; /* Empty statement to make some compilers happy */
>>
>> [1]
>> https://lore.kernel.org/xen-devel/98b8c131-b0b9-f46c-5f46-c2136f2e3...@amd.com/
>
> This earlier discussion only proves that there is at least one compiler
> objecting. There's no proof there that any compiler exists which, as a
> language extension, actually permits such syntax. Yet if the comment
> was purely about normal language syntax, then imo it should be zapped
> altogether, not just be shrunk.
I'll zap it
