From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Clark Williams <williams@redhat.com>
Subject: Re: safety of *mutex_unlock() (Was: [BUG] signal: sighand unprotected when accessed by /proc)
Date: Wed, 18 Jun 2014 10:00:38 -0700 [thread overview]
Message-ID: <20140618170038.GQ4669@linux.vnet.ibm.com> (raw)
In-Reply-To: <20140618164359.GA18598@redhat.com>
On Wed, Jun 18, 2014 at 06:43:59PM +0200, Oleg Nesterov wrote:
> On 06/17, Paul E. McKenney wrote:
> >
> > + if (drop_boost_mutex) {
> > + rt_mutex_unlock(&rnp->boost_mtx);
> > complete(&rnp->boost_completion);
>
> Well, I still do not understand this ->boost_completion...
>
> > - /* Wait until boostee is done accessing mtx before reinitializing. */
> > + /* Wait for boostee to be done w/boost_mtx before reinitializing. */
> > wait_for_completion(&rnp->boost_completion);
>
> OK, at least we have a comment.
>
> But let me repeat. Thomas has already fixed rt_mutex, unlock is atomic.
> It doesn't touch this memory after it makes another lock() possible.
>
> And (contrary to what I said initially) we can rely on this because -rt
> converts spinlock_t into rt_mutex ?
Well, perhaps I should rein in my paranoia on this one. That said, the
cost of my paranoia is minimal in this slowpath.
Thanx, Paul
next prev parent reply other threads:[~2014-06-18 17:00 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-03 17:02 [BUG] signal: sighand unprotected when accessed by /proc Steven Rostedt
2014-06-03 17:26 ` Oleg Nesterov
2014-06-03 18:03 ` Linus Torvalds
2014-06-03 20:01 ` Oleg Nesterov
2014-06-03 20:03 ` Oleg Nesterov
2014-06-06 20:33 ` Paul E. McKenney
2014-06-08 13:07 ` safety of *mutex_unlock() (Was: [BUG] signal: sighand unprotected when accessed by /proc) Oleg Nesterov
2014-06-09 16:26 ` Paul E. McKenney
2014-06-09 18:15 ` Oleg Nesterov
2014-06-09 18:29 ` Steven Rostedt
2014-06-09 18:51 ` Linus Torvalds
2014-06-09 19:41 ` Steven Rostedt
2014-06-10 8:53 ` Thomas Gleixner
2014-06-10 16:57 ` Oleg Nesterov
2014-06-10 18:08 ` Thomas Gleixner
2014-06-10 18:13 ` Steven Rostedt
2014-06-10 20:05 ` Thomas Gleixner
2014-06-10 20:13 ` Thomas Gleixner
2014-06-11 15:52 ` Paul E. McKenney
2014-06-11 17:07 ` Oleg Nesterov
2014-06-11 17:17 ` Oleg Nesterov
2014-06-11 17:29 ` Paul E. McKenney
2014-06-11 17:59 ` Oleg Nesterov
2014-06-11 19:56 ` Paul E. McKenney
2014-06-12 17:28 ` Oleg Nesterov
2014-06-12 20:35 ` Paul E. McKenney
2014-06-12 21:40 ` Thomas Gleixner
2014-06-12 22:27 ` Paul E. McKenney
2014-06-12 23:19 ` Paul E. McKenney
2014-06-13 15:08 ` Oleg Nesterov
2014-06-15 5:40 ` Paul E. McKenney
2014-06-17 18:57 ` Paul E. McKenney
2014-06-18 16:43 ` Oleg Nesterov
2014-06-18 16:53 ` Steven Rostedt
2014-06-21 19:54 ` Thomas Gleixner
2014-06-18 17:00 ` Paul E. McKenney [this message]
2014-06-13 14:55 ` Oleg Nesterov
2014-06-13 16:10 ` Thomas Gleixner
2014-06-13 16:19 ` Oleg Nesterov
2014-06-13 14:52 ` Oleg Nesterov
2014-06-11 17:27 ` Paul E. McKenney
2014-06-10 17:07 ` Oleg Nesterov
2014-06-10 17:51 ` Thomas Gleixner
2014-06-10 12:56 ` Paul E. McKenney
2014-06-10 14:48 ` Peter Zijlstra
2014-06-10 15:18 ` Paul E. McKenney
2014-06-10 15:35 ` Linus Torvalds
2014-06-10 16:15 ` Paul E. McKenney
2014-06-09 19:04 ` Oleg Nesterov
2014-06-10 8:37 ` Peter Zijlstra
2014-06-10 12:52 ` Paul E. McKenney
2014-06-10 13:01 ` Peter Zijlstra
2014-06-10 14:36 ` Paul E. McKenney
2014-06-10 15:20 ` Paul E. McKenney
2014-06-03 20:05 ` [BUG] signal: sighand unprotected when accessed by /proc Steven Rostedt
2014-06-03 20:09 ` Oleg Nesterov
2014-06-03 20:15 ` Steven Rostedt
2014-06-03 20:25 ` Steven Rostedt
2014-06-03 21:12 ` Thomas Gleixner
2014-06-03 18:05 ` Steven Rostedt
2014-06-03 19:25 ` Oleg Nesterov
2014-06-04 1:16 ` Steven Rostedt
2014-06-04 16:31 ` Oleg Nesterov
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