aio_cancel

aio_cancel

[Jon Grant]

Hello

I have a query about the ask about the aio_cancel description please.

http://man7.org/linux/man-pages/online/pages/man3/aio_cancel.3.html

"Normal asynchronous notification occurs for canceled requests.  The request
       return status is set to -1, and the request error status is set
to ECANCELED."

I would like to ask about this description. Could the detail of
"request return status" and "request error status" be described
please.

My assumption

"request return status" -- perhaps the value returned by aio_return()?
"request error status" -- not sure. maybe aio_error() ?

Thank you for taking a look into this.

Best regards, Jon
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Re: aio_cancel

[Michael Kerrisk]

Hi Jon,

On Tue, Oct 4, 2011 at 12:03 AM, Jon Grant <jg-hus3n9K41k0@public.gmane.org> wrote:
> Hello
>
> I have a query about the ask about the aio_cancel description please.
>
> http://man7.org/linux/man-pages/online/pages/man3/aio_cancel.3.html
>
> "Normal asynchronous notification occurs for canceled requests.  The request
>       return status is set to -1, and the request error status is set
> to ECANCELED."
>
> I would like to ask about this description. Could the detail of
> "request return status" and "request error status" be described
> please.
>
> My assumption
>
> "request return status" -- perhaps the value returned by aio_return()?
> "request error status" -- not sure. maybe aio_error() ?
>
> Thank you for taking a look into this.

Your assumption is correct. I added some words to the man page for
version 3.35 to clarify this.

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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Re: aio_cancel

[Jon Grant]

Michael Kerrisk wrote, On 04/10/11 06:42:
> Hi Jon,
>
> On Tue, Oct 4, 2011 at 12:03 AM, Jon Grant<jg-hus3n9K41k0@public.gmane.org>  wrote:
>> Hello
>>
>> I have a query about the ask about the aio_cancel description please.
>>
>> http://man7.org/linux/man-pages/online/pages/man3/aio_cancel.3.html
>>
>> "Normal asynchronous notification occurs for canceled requests.  The request
>>        return status is set to -1, and the request error status is set
>> to ECANCELED."
>>
>> I would like to ask about this description. Could the detail of
>> "request return status" and "request error status" be described
>> please.
>>
>> My assumption
>>
>> "request return status" -- perhaps the value returned by aio_return()?
>> "request error status" -- not sure. maybe aio_error() ?
>>
>> Thank you for taking a look into this.
>
> Your assumption is correct. I added some words to the man page for
> version 3.35 to clarify this.

Looks good.

Could I ask a related question. When an aio block is cancelled, is there 
anyway to get back the byte count that was processed? e.g. aio_read, the 
number of bytes read before the operation was cancelled.

Best regards, Jon
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Re: aio_cancel

[Michael Kerrisk]

On Wed, Oct 5, 2011 at 2:08 AM, Jon Grant <jg-hus3n9K41k0@public.gmane.org> wrote:
> Michael Kerrisk wrote, On 04/10/11 06:42:
>>
>> Hi Jon,
>>
>> On Tue, Oct 4, 2011 at 12:03 AM, Jon Grant<jg-hus3n9K41k0@public.gmane.org>  wrote:
>>>
>>> Hello
>>>
>>> I have a query about the ask about the aio_cancel description please.
>>>
>>> http://man7.org/linux/man-pages/online/pages/man3/aio_cancel.3.html
>>>
>>> "Normal asynchronous notification occurs for canceled requests.  The
>>> request
>>>       return status is set to -1, and the request error status is set
>>> to ECANCELED."
>>>
>>> I would like to ask about this description. Could the detail of
>>> "request return status" and "request error status" be described
>>> please.
>>>
>>> My assumption
>>>
>>> "request return status" -- perhaps the value returned by aio_return()?
>>> "request error status" -- not sure. maybe aio_error() ?
>>>
>>> Thank you for taking a look into this.
>>
>> Your assumption is correct. I added some words to the man page for
>> version 3.35 to clarify this.
>
> Looks good.
>
> Could I ask a related question. When an aio block is cancelled, is there
> anyway to get back the byte count that was processed? e.g. aio_read, the
> number of bytes read before the operation was cancelled.

Offhand, I don't know. What happens if you try aio_return() +
aio_error()? When you find out, send me a patch!

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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Re: aio_cancel

[Jon Grant]

Michael Kerrisk wrote, On 05/10/11 05:37:
> On Wed, Oct 5, 2011 at 2:08 AM, Jon Grant<jg-hus3n9K41k0@public.gmane.org>  wrote:
[.]
>> Could I ask a related question. When an aio block is cancelled, is there
>> anyway to get back the byte count that was processed? e.g. aio_read, the
>> number of bytes read before the operation was cancelled.
>
> Offhand, I don't know. What happens if you try aio_return() +
> aio_error()? When you find out, send me a patch!

I wrote a small program to write 30MB to a file with aio_write. 
aio_cancel immediately after enqueing. aio_cancel returnend -1, and 
errno was AIO_NOTCANCELED, so I guess it is not possible to cancel in my 
Ubuntu glibc build.



BTW, could this aio_cancel text be updated to clarify if aio_error or 
aio_cancel is returning AIO_ALLDONE.

" This function returns AIO_ALLDONE if
        all requests had already been completed before this call.  When 
some error
        occurs, -1 is returned, and errno is set appropriately."

My assumption would be that it refers to aio_Cancel, but as it follows 
aio_error description.. could be unclear. Maybe the function name can be 
added to the description.


Best regards, Jon
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Re: aio_cancel

[Michael Kerrisk (man-pages)]

[...]
> BTW, could this aio_cancel text be updated to clarify if aio_error or
> aio_cancel is returning AIO_ALLDONE.
>
> " This function returns AIO_ALLDONE if
>       all requests had already been completed before this call.  When some
> error
>       occurs, -1 is returned, and errno is set appropriately."
>
> My assumption would be that it refers to aio_Cancel, but as it follows
> aio_error description.. could be unclear. Maybe the function name can be
> added to the description.

Yes, I've made that change for man-pages-3.40.

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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