Re: kernel error in system call accept() under kernel 2.6.8

[Peter Duellings <Peter.Duellings@wincor-nixdorf.com>]

Alan,


meanwhile we could generate a strace for the problem.
However, I guess that the strace does not give the desired
information (see parts below).

Additionally we added in the program the output of the return
value of the accept() system call . The return value is -512
and the errno value is 0!
Usually the return value should be -1 and the errno  should
contain the value without the sign of the error.


Any idea or comment on this ?

Thanks,


Peter Düllings

---------<strace>------------
2682  09:25:29.238663 accept(21,  <unfinished ...>
2688  09:25:29.263486 accept(33, {sa_family=AF_INET, sin_port=htons(32811),
sin_addr=inet_addr("127.0.0.1")}, [16]) = 40 <27.171270>
2688  09:25:56.589969 accept(33, 0x82fa7e0, [16]) = ? ERESTARTSYS (To be
restarted) <0.385453>
2688  09:25:56.975563 --- SIGCHLD (Child exited) @ 0 (0) ---
2688  09:25:56.975676 accept(33, 0x82fa7e0, [16]) = ? ERESTARTSYS (To be
restarted) <0.205963>
2688  09:25:57.181770 --- SIGCHLD (Child exited) @ 0 (0) ---
2688  09:25:57.181842 accept(33,  <unfinished ...>
2682  09:25:57.231961 <... accept resumed> {sa_family=AF_INET, 
sin_port=htons
(32882), sin_addr=inet_addr("127.0.0.1")}, [16]) = 43 <27.993066>
2682  09:25:57.234320 accept(21,  <unfinished ...>
2688  09:25:57.538314 <... accept resumed> 0x82fa7e0, [16]) = ? ERESTARTSYS
(To be restarted) <0.356435>
2688  09:25:57.538429 --- SIGCHLD (Child exited) @ 0 (0) ---
2688  09:25:57.538488 accept(33, 0x82fa7e0, [16]) = ? ERESTARTSYS (To be
restarted) <0.015688>
2688  09:25:57.554315 --- SIGCHLD (Child exited) @ 0 (0) ---
2688  09:25:57.554370 accept(33, 0x82fa7e0, [16]) = ? ERESTARTSYS (To be
restarted) <0.192660>
2688  09:25:57.747151 --- SIGCHLD (Child exited) @ 0 (0) ---
2688  09:25:57.747236 accept(33, 0x82fa7e0, [16]) = ? ERESTARTSYS (To be
restarted) <0.097813>
....
.
---------</strace>------------



Alan Cox wrote:

> On Maw, 2005-09-20 at 16:25 +0200, Peter Duellings wrote:
>
> > Obviously there are some cases where the accept() system call does
> > not set the errno variable if the accept() system call returns
> > with a value less than zero:
>
>
> Not actually possible. The kernel returns a positive value, zero or a
> negative value which is the errno code negated. It has no mechanism to
> return a negative value and not error.
>
> What does strace show for the failing case ?


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