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RE: [lwip-users] lwip_select() blocks even if timeout is 0
From: |
Chu, Zhenwei |
Subject: |
RE: [lwip-users] lwip_select() blocks even if timeout is 0 |
Date: |
Mon, 6 Oct 2008 14:44:34 -0400 |
The application calls select(), not lwip_select(). The original code is
ported from Linux version.
I think my problem is to set timeout as 0. Make timeout->tv_sec = 0 and
timeout->tv_usec=0, but not timeout, solve the problem.
Thanks for help.
Zhenwei
-----Original Message-----
From: address@hidden
[mailto:address@hidden On Behalf
Of Jonathan Larmour
Sent: Monday, October 06, 2008 2:19 PM
To: Mailing list for lwIP users
Subject: Re: [lwip-users] lwip_select() blocks even if timeout is 0
Chu, Zhenwei wrote:
> Yes, it is lwIP 1.3.0. timeout is set to 0, and timeout->tv_sec = 0
> and timeout->tv_usec=0. The section of code from sockets.c is copied
> here.
I was wondering how you called lwip_select, not the code that's called.
> lwip_select()
> {
> ....
>
> /* add our semaphore to list */
> /* We don't actually need any dynamic memory. Our entry on the
> * list is only valid while we are in this function, so it's ok
> * to use local variables */
>
> select_cb.sem = sys_sem_new(0);
[snip]
But the code that deals with not blocking is in the bit you have cut out
with "....".
As Rishi said, the bit that starts:
/* If we don't have any current events, then suspend if we are
supposed to */
if (!nready) {
if (timeout && timeout->tv_sec == 0 && timeout->tv_usec == 0) {
is the bit which means that lwip_select does not block if the timeout
duration is 0.
Jifl
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