Re: [Cerowrt-devel] TFO crashes cerowrt 3.7.1-1

[Dave Taht <dave.taht@gmail.com>]

I am so buried as to only be able to do new builds of cero once a week.

Can the bad behavior be duplicated on a single core other sort of
processor, like x86? Or merely boot up a x86 box in a single processor
mode?

I'll try to get a new release out next sunday.

On Sun, Jan 13, 2013 at 8:43 PM, Ketan Kulkarni <ketkulka@gmail.com> wrote:
> Thanks Eric and Yuchung for taking care of the patch. I will test few more
> TFO cases as well once this patch is built in cero.
>
> Thanks,
> Ketan
>
> On Jan 14, 2013 9:37 AM, "Eric Dumazet" <edumazet@google.com> wrote:
>>
>> Quite frankly I would just remove the BUG_ON()
>>
>> diff --git a/net/core/request_sock.c b/net/core/request_sock.c
>> index c31d9e8..4425148 100644
>> --- a/net/core/request_sock.c
>> +++ b/net/core/request_sock.c
>> @@ -186,8 +186,6 @@ void reqsk_fastopen_remove(struct sock *sk, struct
>> request_sock *req,
>>         struct fastopen_queue *fastopenq =
>>             inet_csk(lsk)->icsk_accept_queue.fastopenq;
>>
>> -       BUG_ON(!spin_is_locked(&sk->sk_lock.slock) &&
>> !sock_owned_by_user(sk));
>> -
>>         tcp_sk(sk)->fastopen_rsk = NULL;
>>         spin_lock_bh(&fastopenq->lock);
>>         fastopenq->qlen--;
>>
>>
>>
>> On Sun, Jan 13, 2013 at 7:05 PM, Eric Dumazet <edumazet@google.com> wrote:
>>>
>>> Oh well yes, this doesnt quite work on !SMP.
>>>
>>> And this kind of bug is frequent....
>>>
>>> See following example :
>>>
>>> commit b9980cdcf2524c5fe15d8cbae9c97b3ed6385563
>>> Author: Hugh Dickins <hughd@google.com>
>>> Date:   Wed Feb 8 17:13:40 2012 -0800
>>>
>>>     mm: fix UP THP spin_is_locked BUGs
>>>
>>>     Fix CONFIG_TRANSPARENT_HUGEPAGE=y CONFIG_SMP=n CONFIG_DEBUG_VM=y
>>>     CONFIG_DEBUG_SPINLOCK=n kernel: spin_is_locked() is then always
>>> false,
>>>     and so triggers some BUGs in Transparent HugePage codepaths.
>>>
>>>     asm-generic/bug.h mentions this problem, and provides a
>>> WARN_ON_SMP(x);
>>>     but being too lazy to add VM_BUG_ON_SMP, BUG_ON_SMP,
>>> WARN_ON_SMP_ONCE,
>>>     VM_WARN_ON_SMP_ONCE, just test NR_CPUS != 1 in the existing
>>> VM_BUG_ONs.
>>>
>>>     Signed-off-by: Hugh Dickins <hughd@google.com>
>>>     Cc: Andrea Arcangeli <aarcange@redhat.com>
>>>     Cc: <stable@vger.kernel.org>
>>>     Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>>>     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>>>
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index b3ffc21..91d3efb 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -2083,7 +2083,7 @@ static void collect_mm_slot(struct mm_slot
>>> *mm_slot)
>>>  {
>>>         struct mm_struct *mm = mm_slot->mm;
>>>
>>> -       VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
>>> +       VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
>>>
>>>
>>>
>>>
>>> On Sun, Jan 13, 2013 at 1:39 PM, Felix Fietkau <nbd@openwrt.org> wrote:
>>>>
>>>> On 2013-01-13 7:03 PM, Eric Dumazet wrote:
>>>> > I suspect a bug in the spin_is_locked() implementation on your arch,
>>>> > as
>>>> > he socket lock should be held at this point.
>>>> I don't think this is an arch implementation bug, this probably happens
>>>> on all !SMP systems. See this bit from include/linux/spinlock_up.h:
>>>>
>>>> #define arch_spin_is_locked(lock)   ((void)(lock), 0)
>>>>
>>>> - Felix
>>>>
>>>
>>
>
>
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-- 
Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html