From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
RT <linux-rt-users@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Clark Williams <williams@redhat.com>
Subject: Re: [RFC][PATCH RT] rwsem_rt: Another (more sane) approach to mulit reader rt locks
Date: Tue, 15 May 2012 13:25:32 -0400 [thread overview]
Message-ID: <1337102732.14207.336.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <1337096542.14207.315.camel@gandalf.stny.rr.com>
On Tue, 2012-05-15 at 11:42 -0400, Steven Rostedt wrote:
> On Tue, 2012-05-15 at 17:06 +0200, Peter Zijlstra wrote:
> > On Tue, 2012-05-15 at 10:03 -0400, Steven Rostedt wrote:
> > >
> > > where readers may nest (the same task may grab the same rwsem for
> > > read multiple times), but only one task may hold the rwsem at any
> > > given
> > > time (for read or write).
> >
> > Humm, that sounds iffy, rwsem isn't a recursive read lock only rwlock_t
> > is.
>
> In that case, current -rt is broken. As it has it being a recursive lock
> (without my patch).
>
Why wouldn't it be recursive. If two different tasks are allowed to grab
a read lock at the same time, why can't the same task grab a read lock
twice? As long as it releases it the same amount of times.
Now you can't grab a read lock if you have the write lock.
-- Steve
next prev parent reply other threads:[~2012-05-15 17:25 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-15 14:03 [RFC][PATCH RT] rwsem_rt: Another (more sane) approach to mulit reader rt locks Steven Rostedt
2012-05-15 15:06 ` Peter Zijlstra
2012-05-15 15:42 ` Steven Rostedt
2012-05-15 17:25 ` Steven Rostedt [this message]
2012-05-15 17:31 ` Peter Zijlstra
2012-05-15 17:43 ` Steven Rostedt
2012-05-15 16:26 ` Steven Rostedt
2012-05-15 18:00 ` John Kacur
2012-05-15 18:14 ` Steven Rostedt
2012-05-17 15:18 ` Paul E. McKenney
2012-05-17 15:25 ` Paul E. McKenney
2012-05-17 15:32 ` Peter Zijlstra
2012-05-17 15:47 ` Paul E. McKenney
2012-05-17 16:17 ` Peter Zijlstra
2012-05-17 20:08 ` Paul E. McKenney
2012-05-17 20:20 ` Peter Zijlstra
2012-05-22 15:26 ` Thomas Gleixner
2012-05-22 15:50 ` Steven Rostedt
2012-05-22 16:40 ` Thomas Gleixner
2012-05-22 16:52 ` Steven Rostedt
2012-05-22 17:07 ` Thomas Gleixner
2012-05-22 17:50 ` Steven Rostedt
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