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To: Joachim Fenkes <fenkes@de.ibm.com>
Subject: Re: [PATCH] eHCA: Add "Modify Port" verb
References: <200704231823.48723.fenkes@de.ibm.com>
From: Roland Dreier <rdreier@cisco.com>
Date: Mon, 23 Apr 2007 12:20:14 -0700
In-Reply-To: <200704231823.48723.fenkes@de.ibm.com> (Joachim Fenkes's message
	of "Mon, 23 Apr 2007 18:23:48 +0200")
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 > +	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.

You could look at the implementation in mthca to see the locking I
used there.

 - R.