[9fans] A question about timeout

[9fans] A question about timeout

[Adriano Verardo]

I'm porting some Unix applications which implement a timeout on
read/write/accept/... calls using select().

In previous versions I did the same by signals but with problems
due to the behaviour  of the interrupted system call.

Select() is also used to choose among channels waiting for I/O.

How can I implement channel selection and secure timeouts
without using APE ?

Re-write some pieces is not a problem, I prefer a "pure" 8c implementation.


adriano

Re: [9fans] A question about timeout

[cinap_lenrek]

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to interrupt on i/o operations you send a note to the process.
for ioproc(2), here is iointerrupt() that does that. for timeouts here is
a alarm() function (see sleep(2)) that will fire a note on you when the alarm expires.
notes should also work for rendezvous()/alt(), but a better way is to include
a timeout/cancel channel in your alt() operation. as a example see
/sys/src/cmd/rio/time.c. here we have a central timer process
that does a sleep and sends a message to channels associated
with timers when they expire.

--
cinap

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From: Adriano Verardo <a.verardo@tecmav.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: [9fans] A question about timeout
Date: Tue, 14 Jul 2009 16:21:08 +0200
Message-ID: <4A5C9454.9080801@tecmav.com>

I'm porting some Unix applications which implement a timeout on
read/write/accept/... calls using select().

In previous versions I did the same by signals but with problems
due to the behaviour  of the interrupted system call.

Select() is also used to choose among channels waiting for I/O.

How can I implement channel selection and secure timeouts
without using APE ?

Re-write some pieces is not a problem, I prefer a "pure" 8c implementation.


adriano

Re: [9fans] A question about timeout

[Adriano Verardo]

cinap_lenrek@gmx.de wrote:
> to interrupt on i/o operations you send a note to the process.
> for ioproc(2), here is iointerrupt() that does that. for timeouts here is
> a alarm() function (see sleep(2)) that will fire a note on you when the alarm expires.
> notes should also work for rendezvous()/alt(), but a better way is to include
> a timeout/cancel channel in your alt() operation. as a example see
> /sys/src/cmd/rio/time.c. here we have a central timer process
> that does a sleep and sends a message to channels associated
> with timers when they expire.
>
> --
> cinap

Thank you very much.

Where can I find the explanation of the interrupted system calls behaviour ?
In Unix I sometimes found quite difficult to deal with them.
What about Plan9 ?

adriano

Re: [9fans] A question about timeout

[cinap_lenrek]

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its best to look at the manpage for the function to check
what happens in the case of interruption. but they usualy
just return -1 and set errstr will contain the string
"interrupted". plan9 does no syscall restarting.

read notify(2) and thread(2).

--
cinap

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From: Adriano Verardo <a.verardo@tecmav.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] A question about timeout
Date: Tue, 14 Jul 2009 19:41:27 +0200
Message-ID: <4A5CC347.7080806@tecmav.com>

cinap_lenrek@gmx.de wrote:
> to interrupt on i/o operations you send a note to the process.
> for ioproc(2), here is iointerrupt() that does that. for timeouts here is
> a alarm() function (see sleep(2)) that will fire a note on you when the alarm expires.
> notes should also work for rendezvous()/alt(), but a better way is to include
> a timeout/cancel channel in your alt() operation. as a example see
> /sys/src/cmd/rio/time.c. here we have a central timer process
> that does a sleep and sends a message to channels associated
> with timers when they expire.
>
> --
> cinap

Thank you very much.

Where can I find the explanation of the interrupted system calls behaviour ?
In Unix I sometimes found quite difficult to deal with them.
What about Plan9 ?

adriano