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

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Date:	Mon, 23 Apr 2007 12:20:14 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	Joachim Fenkes <fenkes@...ibm.com>
Cc:	"LinuxPPC-Dev" <linuxppc-dev@...abs.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"OF-General" <general@...ts.openfabrics.org>,
	Roland Dreier <rolandd@...co.com>,
	"Hoang-Nam Nguyen" <hnguyen@...ibm.com>
Subject: Re: [PATCH] eHCA: Add "Modify Port" verb

 > +	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.
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