linux-kernel - Re: [PATCH] eHCA: Add "Modify Port" verb

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Date:	Tue, 24 Apr 2007 14:25:34 +0200
From:	Joachim Fenkes <FENKES@...ibm.com>
To:	Roland Dreier <rdreier@...co.com>
Cc:	"OF-General" <general@...ts.openfabrics.org>,
	Hoang-Nam Nguyen <hnguyen@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"LinuxPPC-Dev" <linuxppc-dev@...abs.org>,
	Roland Dreier <rolandd@...co.com>
Subject: Re: [PATCH] eHCA: Add "Modify Port" verb

Roland Dreier <rdreier@...co.com> wrote on 23.04.2007 21:20:14:

>  > +   if (hipz_h_query_port(shca->ipz_hca_handle, port, rblock) != 
H_SUCCESS) {
>  > +      ehca_err(&shca->ib_device, "Can't query port properties");
>  > +      ret = -EINVAL;
>  > +      goto modify_port1;
>  > +   }
>  > +
>  > +   cap = (rblock->capability_mask | props->set_port_cap_mask)
>  > +      & ~props->clr_port_cap_mask;
>  > +
>  > +   hret = hipz_h_modify_port(shca->ipz_hca_handle, port,
>  > +              cap, props->init_type, port_modify_mask);
> 
> Is this thread-safe?  What if two different bits are set at the same
> time from two different threads?  It seems that both calls could get
> the same result from hipz_h_query_port(), and then the second call to
> hipz_h_modify_port() would overwrite the first call.

Yes, you're so right.
 
> You could look at the implementation in mthca to see the locking I
> used there.

I'll do that, thanks for the hint!

Joachim

---
Joachim Fenkes  --  eHCA Linux Driver Developer and Hardware Tamer
IBM Deutschland Entwicklung GmbH  --  Dept. 3627 (I/O Firmware Dev. 2)
Schoenaicher Strasse 220  --  71032 Boeblingen  --  Germany
eMail: fenkes@...ibm.com  --  Phone: +49 7031 16 1239 
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