[PATCH 0/1] Update _PC_ASYNC_IO return value
Thu Jul 26 08:52:00 GMT 2018
On Thu, 26 Jul 2018, Corinna Vinschen wrote:
> On Jul 25 15:06, Yaakov Selkowitz wrote:
>>> From discussion on IRC:
>> <yselkowitz> corinna, just sent a patch for _POSIX_ASYNCHRONOUS_IO as a
>> follow-up to the AIO feature, but am still wondering about
>> <corinna> in terms of _PC_ASYNC_IO, the test might be a bit tricky
>> <corinna> let me check
>> <corinna> actually, no
>> <corinna> it's easy
>> <corinna> Mark implemented the stuff with pread/pwrite only on disk files
>> <corinna> but otherwise it's device independent in that he implemented a
>> workaround for pipes and stuff
>> <corinna> so, in theory we can just return 1
>> I'm not sure how to test this atm, but based on the above I have made
>> the following patch so this doesn't get lost.
>> Yaakov Selkowitz (1):
>> Cygwin: fpathconf: update _PC_ASYNC_IO return value
>> winsup/cygwin/fhandler.cc | 1 +
>> 1 file changed, 1 insertion(+)
> Mark? Any comment you want to make?
Thanks for asking. Your characterization of my implementation is correct.
The intent is for aio_* async I/O to be supported on all descriptors. On
the most useful case of binary local disk files, inline pread|pwrite is
used. But I wanted to make sure the AIO interface would do the right
thing on other kinds of descriptors without bothering the user about it.
So if the intent of the _PC_ASYNC_IO flag is to say that async I/O is
supported generally, I do think setting it to 1 is appropriate. That is,
if it's talking about the aio_* interfaces. If there's an O_ASYNC defined
for app coders, my recent contribution doesn't address that at all.
Is there a reference I could check for the meaning of the flag? I'll do
an online search in the meantime.
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