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From: "Paul E. McKenney" <paulmck@kernel.org>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	rcu@vger.kernel.org, Josh Triplett <josh@joshtriplett.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mike Galbraith <efault@gmx.de>,
	urezki@gmail.com
Subject: Re: [PATCH 1/3] rcu: Use static initializer for krc.lock
Date: Thu, 16 Apr 2020 14:00:57 -0700	[thread overview]
Message-ID: <20200416210057.GY17661@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200416203637.GA176663@google.com>

On Thu, Apr 16, 2020 at 04:36:37PM -0400, Joel Fernandes wrote:
> On Thu, Apr 16, 2020 at 03:26:23PM -0400, Steven Rostedt wrote:
> > On Thu, 16 Apr 2020 14:59:34 -0400
> > Joel Fernandes <joel@joelfernandes.org> wrote:
> > 
> > > But, then will it be safe for kfree_rcu() callers from hard IRQ context to
> > > call this in PREEMPT_RT? That could would just break then as you cannot sleep
> > > in hard IRQ context even on PREEMPT_RT.
> > 
> > But where in PREEMPT_RT would it be called in hard IRQ context?
> 
> I am not saying that it is called now, but in the future if it is called for
> an interrupt that is not threaded on -rt, it would be a problem right?
> 
> > Note, most interrupt handlers in PREEMPT_RT are turned into threads (except
> > for a very few, which shouldn't be calling kfree_rcu()).
> 
> Yes those very few is what I was referring to. It also sounds like from the
> other thread, Paul is saying it should be allowed to be called from some
> contexts that are not sleepable. In those cases also the rtmutex will fall
> apart.

We might need different calling-context restrictions for the two variants
of kfree_rcu().  And we might need to come up with some sort of lockdep
check for "safe to use normal spinlock in -rt".

							Thanx, Paul

  reply	other threads:[~2020-04-16 21:00 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-15 16:00 [PATCH 0/3] rcu: Static initializer + misc Sebastian Andrzej Siewior
2020-04-15 16:00 ` [PATCH 1/3] rcu: Use static initializer for krc.lock Sebastian Andrzej Siewior
2020-04-16 14:42   ` Joel Fernandes
2020-04-16 15:01     ` Uladzislau Rezki
2020-04-16 15:20       ` Sebastian Andrzej Siewior
2020-04-16 15:38         ` Uladzislau Rezki
2020-04-16 15:46           ` Sebastian Andrzej Siewior
2020-04-16 16:01             ` Uladzislau Rezki
2020-04-16 16:11               ` Sebastian Andrzej Siewior
2020-04-16 16:18                 ` Uladzislau Rezki
2020-04-16 16:33                   ` Sebastian Andrzej Siewior
2020-04-16 17:29                     ` Paul E. McKenney
2020-04-16 18:23                       ` Sebastian Andrzej Siewior
2020-04-16 18:29                         ` Paul E. McKenney
2020-04-16 18:43                           ` Joel Fernandes
2020-04-16 20:56                             ` Sebastian Andrzej Siewior
2020-04-16 21:04                               ` Joel Fernandes
2020-04-16 21:07                                 ` Sebastian Andrzej Siewior
2020-04-16 18:40                     ` Steven Rostedt
2020-04-16 18:53                       ` Joel Fernandes
2020-04-16 19:24                         ` Steven Rostedt
2020-04-16 20:41                           ` Joel Fernandes
2020-04-16 21:05                       ` Sebastian Andrzej Siewior
2020-04-16 17:28         ` Paul E. McKenney
2020-04-16 15:18     ` Sebastian Andrzej Siewior
2020-04-16 18:41       ` Joel Fernandes
2020-04-16 18:59         ` Joel Fernandes
2020-04-16 19:26           ` Steven Rostedt
2020-04-16 19:53             ` Paul E. McKenney
2020-04-16 20:05               ` Uladzislau Rezki
2020-04-16 20:25                 ` Paul E. McKenney
2020-04-16 21:02                   ` Joel Fernandes
2020-04-16 21:18                   ` Uladzislau Rezki
2020-04-16 21:26                     ` Uladzislau Rezki
2020-04-16 21:28                   ` Sebastian Andrzej Siewior
2020-04-16 20:36             ` Joel Fernandes
2020-04-16 21:00               ` Paul E. McKenney [this message]
2020-04-16 21:34                 ` Sebastian Andrzej Siewior
2020-04-17  3:05                   ` Joel Fernandes
2020-04-17  8:47                     ` Uladzislau Rezki
2020-04-17 15:04                     ` Sebastian Andrzej Siewior
2020-04-17 18:26                       ` Joel Fernandes
2020-04-17 18:54                         ` Paul E. McKenney
2020-04-18 12:37                           ` Uladzislau Rezki
2020-04-19 14:58                             ` Paul E. McKenney
2020-04-20  0:27                               ` Joel Fernandes
2020-04-20  1:17                                 ` Joel Fernandes
2020-04-20  1:44                                   ` Paul E. McKenney
2020-04-20 12:13                                     ` Uladzislau Rezki
2020-04-20 12:36                                       ` joel
2020-04-20 13:00                                         ` Uladzislau Rezki
2020-04-20 13:26                                           ` Paul E. McKenney
2020-04-20 16:08                                             ` Uladzislau Rezki
2020-04-20 16:25                                               ` Paul E. McKenney
2020-04-20 16:29                                                 ` Uladzislau Rezki
2020-04-20 16:46                                                   ` Paul E. McKenney
2020-04-20 16:59                                                     ` Uladzislau Rezki
2020-04-20 17:21                                                       ` Paul E. McKenney
2020-04-20 17:40                                                         ` Uladzislau Rezki
2020-04-20 17:57                                                           ` Joel Fernandes
2020-04-20 18:13                                                             ` Paul E. McKenney
2020-04-20 17:59                                                           ` Paul E. McKenney
2020-04-20 19:06                                                             ` Uladzislau Rezki
2020-04-20 20:17                                                               ` Uladzislau Rezki
2020-04-20 22:16                                                                 ` Paul E. McKenney
2020-04-21  1:22                                                                 ` Steven Rostedt
2020-04-21  5:18                                                                   ` Uladzislau Rezki
2020-04-21 13:30                                                                     ` Steven Rostedt
2020-04-21 13:45                                                                       ` Uladzislau Rezki
2020-04-21 13:39                                                           ` Sebastian Andrzej Siewior
2020-04-21 15:41                                                             ` Paul E. McKenney
2020-04-21 17:05                                                               ` Sebastian Andrzej Siewior
2020-04-21 18:09                                                                 ` Paul E. McKenney
2020-04-22 11:13                                                                   ` Sebastian Andrzej Siewior
2020-04-22 13:33                                                                     ` Paul E. McKenney
2020-04-22 15:46                                                                       ` Sebastian Andrzej Siewior
2020-04-22 16:19                                                                         ` Paul E. McKenney
2020-04-22 16:35                                                                           ` Paul E. McKenney
2020-04-20  3:02                                   ` Mike Galbraith
2020-04-20 12:30                                     ` joel
2020-04-17 16:11                     ` Uladzislau Rezki
2020-04-19 12:15                     ` Uladzislau Rezki
2020-04-15 16:00 ` [PATCH 2/3] rcu: Use consistent locking around kfree_rcu_drain_unlock() Sebastian Andrzej Siewior
2020-04-15 16:00 ` [PATCH 3/3] rcu: Avoid using xchg() in kfree_call_rcu_add_ptr_to_bulk() Sebastian Andrzej Siewior
2020-04-20 15:23   ` Joel Fernandes

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