Re: Witness warning with SCTP

From: Robert Watson <rwatson_at_FreeBSD.org>
Date: Sun, 7 Jan 2007 18:54:18 +0000 (GMT)
On Sun, 7 Jan 2007, Randall Stewart wrote:

> Craig:
>
> When we allocate a PCB we hold several locks. This prevents a conflict of 
> say a sender allocating a PCB at the very same instant (this was one of my 
> race condition bugs that was fixed recently).
>
> Now, each PCB has a small hash table it uses. We call hashinit() for this ..
>
> hashinit() does a malloc with M_WAITOK
>
> thus the warning.
>
> So, I either need to make another hashinit() function with a passed flag for 
> the wait (seems the best way) OR make a sctp specific hashinit.. which I 
> don't like doing..
>
> Maybe I can change the name of hashinit() to hashinit_x() and then make 
> hashinit() be a macro that calls hasinit_x with M_WAITOK.. then I could use 
> hashinit_x() directly?
>
> Don't know what the best course is to go here...
>
> It is rather strange that I have not seen this, since like I said one of my 
> machines is running with witness enabled .. hmm..
>
> Anyway.. advice from others how I should proceed would be welcome..
>
> hashinit_x() or an sctp specific hash_init??

I think my preference would be to see a hashinit_flags() or the like, and have 
a wait argument to that.  I'd be tempted to give it a new name, like 
HASH_WAITOK or such, in case we want to add other flags in the future.

Remember to update hashinit(9). :-)

Robert N M Watson
Computer Laboratory
University of Cambridge

>
> R
>
> Craig Rodrigues wrote:
>> Hi,
>> 
>> I am running one of the SCTP tests in the ACE library,
>> and am getting the following witness warning.  Any ideas what the cause
>> is?
>> 
>> Thanks.
>> 
>> malloc(M_WAITOK) of "1024", forcing M_NOWAIT with the following 
>> non-sleepable locks held:
>> exclusive sleep mutex sctp-create (inp_create) r = 0 (0xc2ddded0) locked _at_ 
>> /usr/src/sys/netinet/sctp_input.c:4006
>> KDB: stack backtrace:
>> db_trace_self_wrapper(c09bf21a) at db_trace_self_wrapper+0x25
>> kdb_backtrace(1,400,c146d5a0,6,cbd70148,...) at kdb_backtrace+0x29
>> witness_warn(5,0,c09dac6c,c09701c9) at witness_warn+0x192
>> uma_zalloc_arg(c146d5a0,0,2) at uma_zalloc_arg+0x41
>> malloc(400,c0a50840,2,c28cf3e4,cbd701ac,...) at malloc+0xb2
>> hashinit(100,c0a50840,c2dde80c,f1,c28cf3e4,...) at hashinit+0x3b
>> sctp_inpcb_alloc(c28cf3e4) at sctp_inpcb_alloc+0x143
>> sctp_attach(c28cf3e4,0,0) at sctp_attach+0x34
>> sonewconn(c28a9530,2,c2ddff48,0,c09cf2c5,839) at sonewconn+0x119
>> sctp_handle_cookie_echo(c297e900,14,20,c297e948,cbd70390,cbd70bbc,cbd70bc0,cbd70c20,0,0,0,cbd70384) 
>> at sctp_handle_cookie_echo+0x77e
>> sctp_process_control(c297e900,14,cbd70c08,1ac,c297e948,c297e954,c2dddc10,c2ddfa50,cbd70c20,cbd70be8) 
>> at sctp_process_control+0xd89
>> sctp_common_input_processing(cbd70c3c,14,20,1ac,c297e948,c297e954,c2dddc10,0,c2de1570,0) 
>> at sctp_common_input_processing+0x72
>> sctp_input(c297e900,14,ae,100007f,0,...) at sctp_input+0x2fa
>> ip_input(c297e900) at ip_input+0x5c5
>> netisr_processqueue(c0af3658) at netisr_processqueue+0x6e
>> swi_net(0) at swi_net+0xc2
>> ithread_execute_handlers(c210b6c0,c2129900) at 
>> ithread_execute_handlers+0x11e
>> ithread_loop(c20ed960,cbd70d38) at ithread_loop+0x67
>> fork_exit(c06bbd2c,c20ed960,cbd70d38) at fork_exit+0xac
>> fork_trampoline() at fork_trampoline+0x8
>> 
>
>
> -- 
> Randall Stewart
> NSSTG - Cisco Systems Inc.
> 803-345-0369 <or> 803-317-4952 (cell)
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Received on Sun Jan 07 2007 - 17:54:22 UTC

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