linux-kernel - Re: [ofa-general] [PATCH] [WORKAROUND] CONFIG_PREEMPT_RT and ib_umad

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <adair69nf7r.fsf@cisco.com>
Date:	Mon, 17 Sep 2007 14:40:08 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	john.blackwood@...r.com
Cc:	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Sven-Thorsten Dietrich <sdietrich@...ell.com>,
	general@...ts.openfabrics.org
Subject: Re: [ofa-general] [PATCH] [WORKAROUND] CONFIG_PREEMPT_RT and ib_umad_close() issue

Thanks for the explanation...

 > But basically, with CONFIG_PREEMPT_RT enabled, the lock points, such as
 > aqcuiring a spinlock, potentially become places where the current task
 > may be context switched out / preempted.
 > 
 > Therefore, when a call is made to lock a spinlock for example, the
 > caller should not currently have irqs disabled, or preemption disabled,
 > since a context switch may occur.

this doesn't seem relevant here...

 > void fastcall rt_downgrade_write(struct rw_semaphore *rwsem)
 > {
 >         BUG();
 > }

this seems to be the problem... the -rt patch turns downgrade_write()
into a BUG().

I need to look at the locking in user_mad.c again, but I think it may
be possible to replace both places that do downgrade_write() with
up_write() followed by down_read().

 - R.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/