linux-kernel - Re: [PATCH 2/2] target: remove spin_lock_assert() in __target_(attach|detach)_tg_pt

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Date:   Fri, 23 Mar 2018 18:50:13 +0100
From:   "bigeasy@...utronix.de" <bigeasy@...utronix.de>
To:     Bart Van Assche <Bart.VanAssche@....com>
Cc:     "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "nab@...ux-iscsi.org" <nab@...ux-iscsi.org>,
        "daniel@...stot.me" <daniel@...stot.me>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "acme@...nel.org" <acme@...nel.org>,
        "williams@...hat.com" <williams@...hat.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "lclaudio@...hat.com" <lclaudio@...hat.com>,
        "target-devel@...r.kernel.org" <target-devel@...r.kernel.org>,
        "linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>
Subject: Re: [PATCH 2/2] target: remove spin_lock_assert() in
 __target_(attach|detach)_tg_pt_gp()

On 2018-03-23 17:44:46 [+0000], Bart Van Assche wrote:
> On Fri, 2018-03-23 at 18:19 +0100, bigeasy@...utronix.de wrote:
> > __target_attach_tg_pt_gp() and __target_detach_tg_pt_gp() check if the caller
> > holds lun_tg_pt_gp_lock(). Both functions are static, the callers are
> > acquiring the lock before the invocation of the function so the check
> > looks superfluous.
> > Remove it.
> 
> Does this check cause trouble to anyone or to a specific kernel configuration?
Those two do not.

> In other words, do we really need to remove these checks? I think that these
> checks are useful as documentation to people who read the SCSI target code.
> The target code is already hard to follow so I think any documentation,
> especially documentation in the form of code that is checked at runtime, is
> welcome.

so if I remove those two and add a kernel doc comment instead, saying
that the caller needs to ensure that "lun->lun_tg_pt_gp_lock" is held
then we would remove the obvious runtime check and add a piece of
documentation. Would that work?

> Thanks,
> 
> Bart.

Sebastian