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Message-ID: <adaps0hnv5a.fsf@cisco.com>
Date: Mon, 17 Sep 2007 08:56:01 -0700
From: Roland Dreier <rdreier@...co.com>
To: John Blackwood <john.blackwood@...r.com>
Cc: linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
general@...ts.openfabrics.org,
Sven-Thorsten Dietrich <sdietrich@...ell.com>
Subject: Re: [ofa-general] [PATCH] [WORKAROUND] CONFIG_PREEMPT_RT and ib_umad_close() issue
> When using OFED-1.2.5 based infiniband kernel modules on 2.6.22 based
> kernels with the Ingo Molnar CONFIG_PREEMPT_RT applied, then commands
> such as ibnetdiscvoer, smpquery, sminfo, etc. will hang. The problem
> is with the downgrade_write() rw semaphore usage in the
> ib_umad_close() routine.
Can you give a few more details on how PREEMPT_RT changes locking
rules (or just exposes existing bugs maybe?) so that the
downgrade_write() causes the issue? I would like to fix this cleanly
but I don't really understand what the problem is.
- R.
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