linux-kernel - Re: cciss

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Message-ID: <CAPDOMVhrZe+_ewQQe1y-pam=3rNtF8tjMt3Kgprc3WavVur1QQ@mail.gmail.com>
Date:	Wed, 23 Jul 2014 11:38:06 -0400
From:	Nick Krause <xerofoify@...il.com>
To:	scameron@...rdog.cce.hp.com
Cc:	Randy Dunlap <rdunlap@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	scott.benesh@...com, iss_storagedev@...com,
	michael.miller@...onical.com
Subject: Re: cciss_scsi.c: Fix me

On Wed, Jul 23, 2014 at 11:19 AM,  <scameron@...rdog.cce.hp.com> wrote:
> On Wed, Jul 23, 2014 at 08:11:33AM -0700, Randy Dunlap wrote:
>> On 07/23/2014 07:41 AM, scameron@...rdog.cce.hp.com wrote:
>> > On Wed, Jul 23, 2014 at 02:15:29PM +0000, Benesh, Scott wrote:
>> >> From: Nick Krause [mailto:xerofoify@...il.com]
>> >> Sent: Saturday, July 19, 2014 11:51 PM
>> >> To: mike.miller@...com
>> >> Cc: ISS StorageDev; linux-kernel@...r.kernel.org
>> >> Subject: cciss_scsi.c: Fix me
>> >>
>> >> Hey Mike,
>> >> I seem to be hitting a fix me message in this file in function,cciss_scsi_queue_command_lck.
>> >> I am wondering what you want to do when C is Null?
>> >> Cheers Nick
>> >
>> > Hi Nick,
>> >
>> > Mike's moved on from HP to Canonical now.
>> >
>> > It looks like you're running out of commands for tape drives,
>> > which shouldn't ever happen, since we set
>> >
>> >     sh->can_queue = cciss_tape_cmds;
>> >
>> > and we allocate that many commands + 2....
>> >
>> > scsi_cmd_stack_setup(ctlr_info_t *h, struct cciss_scsi_adapter_data_t *sa)
>> > {
>> >         int i;
>> >         struct cciss_scsi_cmd_stack_t *stk;
>> >         size_t size;
>> >
>> >         stk = &sa->cmd_stack;
>> >         stk->nelems = cciss_tape_cmds + 2;
>> >
>> > You're apparently hitting this:
>> >
>> >         spin_lock_irqsave(&h->lock, flags);
>> >         c = scsi_cmd_alloc(h);
>> >         spin_unlock_irqrestore(&h->lock, flags);
>> >         if (c == NULL) {                        /* trouble... */
>> >                 dev_warn(&h->pdev->dev, "scsi_cmd_alloc returned NULL!\n");
>> >                 /* FIXME: next 3 lines are -> BAD! <- */
>> >                 cmd->result = DID_NO_CONNECT << 16;
>> >                 done(cmd);
>> >                 return 0;
>> >         }
>> >
>> > which means that scsi_cmd_alloc returned NULL, which only happens
>> > if the thing has run out of commands.
>> >
>> > It's not obvious to me how it can be that it runs out of commands.
>> > Maybe we're losing them somehow, but this has not previously been
>> > a problem that I'm aware of.
>> >
>> > Are you able to reproduce the problem?
>> >
>> > What's going on on the system when it happens?
>> >
>> > putting in a dump_stack(); near that FIXME might give a clue.
>> >
>> > Which kernel are you running?
>> >
>> > -- steve
>>
>> Hi Steve,
>>
>> You apparently have not been following the Nick saga.
>>
>> Nick is using cscope to search for FIXMEs in the kernel source tree and
>> then trying to generate patches to remove or 'fix' them.
>>
>> He is not hitting a kernel oops or panic or bug.
>
> Ah, ok, thanks.  That explains it, because I was pretty sure that
> code is a "this will never happen" case.
>
> -- steve
>


Fine I give up you guys don't want me to touch these fix mes and leave
them alone.
Cheers Nick
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