Re: CVS commit: src/sys/netinet

[Ryota Ozaki <ozaki-r%netbsd.org@localhost>]

On Tue, Dec 26, 2017 at 4:50 PM, Tom Ivar Helbekkmo
<tih%hamartun.priv.no@localhost> wrote:
> Ryota Ozaki <ozaki-r%NetBSD.org@localhost> writes:
>
>> One possible fix has been committed.
>>
>> Can you update the source code and try a new kernel?
>
> Will do.

Thanks.


>
> Meanwhile, before I got around to building a kernel with debug options
> enabled, I had another hang.  Got it into DDB successfully, but then I
> managed, while looking for a way to switch between CPUs (the man page is
> wrong in this respect), to get DDB to look at something it shouldn't
> have, so it just said "fatal pag", and that was that.
>
> I did get a backtrace of CPU 0, though, and it looked interesting:
>
> pool_catchup()
> pool_get()
> pool_cache_get_slow()
> pool_cache_get_paddr()
> m_get()
> m_gethdr()
> wm_add_rxbuf()
> wm_rxeof()
> wm_intr_legacy()
> intr_biglock_wrapper()
> Xintr_ioapic_level2()
> --- interrupt ---
> Xspllower()
> uvm_km_kmem_alloc()
> pool_page_alloc()
> pool_grow()
> pool_catchup()
> pool_get()
> pool_cache_get_slow()
> pool_cache_get_paddr()
> m_get()
> m_gethdr()
> tcp_output()
> tcp_send_wrapper()
> sosend()
> soo_write()
> dofilewrite()
> sys_write()
> syscall()
> --- syscall (number 4) ---

Looks the below infinite loop is happening?

I think we need to summon a pool expert.

  ozaki-r


(Copied and modified the diagram from PR 52858)

 [lwp #1]
    |
 [pool_grow with PR_NOWAIT
 [set PR_GROWING and PR_GROWINGNOWAIT
 [mutex_exit(&pp->pr_lock)
    |
 (interrupted)

 [intr #1]
    |
 [pool_catchup
 [pool_grow with PR_NOWAIT
 [see PR_GROWING and PR_GROWINGNOWAIT are set
 [return ERESTART
 [repeat pool_grow in pool_catchup...