sock_sendmsg() from a kernel thread question

sock_sendmsg() from a kernel thread question

[captain smp]

I am trying to call sock_sendmsg() from a kernel thread
and it seems to work fine on a UP system but on SMP system
it hangs up and the thread can't even accept a SIGKILL.
It it stuck after the following calls happen:

sock_sendmsg()
sock->ops->sendmsg()
tcp_do_sendmsg()

then tcp_do_sendmsg() calls:

skb = sock_wmalloc(sk, tmp, 0, GFP_KERNEL);

but that call never returns.  It doesn't get to
the code where the comment says: "If we didn't get
any memory, we need to sleep."

I've mucked with sock->sk->allocation flavors but to no avail.

BTW, this is 2.2.16-22 (stock red hat 6.2 kernel)

Is this fixed in later kernels, or is there some semaphore/spinlock
needed to call sock_sendmsg()/recvmsg() from kernel threads?

Is there a race with skbuff allocation/deallocation from the
NET_BH network bottom half handler or NIC interrupt handler
that I can prevent from happening somehow?

-Captain


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Re: sock_sendmsg() from a kernel thread question

[Pete Zaitcev]

> I am trying to call sock_sendmsg() from a kernel thread
> and it seems to work fine on a UP system but on SMP system
> it hangs up and the thread can't even accept a SIGKILL.
> It it stuck after the following calls happen:
> 
> sock_sendmsg()
> sock->ops->sendmsg()
> tcp_do_sendmsg()

Always worked fine for me. I think something is up with
your code. Care to post a relevant snippet?

-- Pete