From: Josh Triplett <josh@joshtriplett.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org
Subject: Re: [PATCH tip/core/rcu 02/26] rcu: New rcu_user_enter_irq() and rcu_user_exit_irq() APIs
Date: Fri, 31 Aug 2012 12:13:21 -0700 [thread overview]
Message-ID: <20120831191321.GQ4259@jtriplet-mobl1> (raw)
In-Reply-To: <1346360743-3628-2-git-send-email-paulmck@linux.vnet.ibm.com>
On Thu, Aug 30, 2012 at 02:05:19PM -0700, Paul E. McKenney wrote:
> From: Frederic Weisbecker <fweisbec@gmail.com>
>
> In some cases, it is necessary to enter or exit userspace-RCU-idle mode
> from an interrupt handler, for example, if some other CPU sends this
> CPU a resched IPI. In this case, the current CPU would enter the IPI
> handler in userspace-RCU-idle mode, but would need to exit the IPI handler
> after having exited that mode.
>
> To allow this to work, this commit adds two new APIs to TREE_RCU:
>
> - rcu_user_enter_irq(). This must be called from an interrupt between
> rcu_irq_enter() and rcu_irq_exit(). After the irq calls rcu_irq_exit(),
> the irq handler will return into an RCU extended quiescent state.
> In theory, this interrupt is never a nested interrupt, but in practice
> it might interrupt softirq, which looks to RCU like a nested interrupt.
>
> - rcu_user_exit_irq(). This must be called from a non-nesting
> interrupt, interrupting an RCU extended quiescent state, also
> between rcu_irq_enter() and rcu_irq_exit(). After the irq calls
> rcu_irq_exit(), the irq handler will return in an RCU non-quiescent
> state.
These names seem a bit confusing. From the descriptions, it sounds like
you don't always need to pair them; rcu_irq_exit() will return to a
non-quiescent state, unless you call rcu_user_enter_irq and *don't* call
rcu_user_exit_irq. Did I get that semantic right?
Given that, the "enter" and "exit" names seem confusing. This seems
more like a flag you can set and clear, rather than a delimited region
as suggested by an enter/exit pair.
How about something vaguely like rcu_user_irq_set_eqs and
rcu_user_irq_clear_eqs?
- Josh Triplett
next prev parent reply other threads:[~2012-08-31 19:13 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-30 21:05 [PATCH tip/core/rcu 0/26] idle-related changes Paul E. McKenney
2012-08-30 21:05 ` [PATCH tip/core/rcu 01/26] rcu: New rcu_user_enter() and rcu_user_exit() APIs Paul E. McKenney
2012-08-30 21:05 ` [PATCH tip/core/rcu 02/26] rcu: New rcu_user_enter_irq() and rcu_user_exit_irq() APIs Paul E. McKenney
2012-08-31 19:13 ` Josh Triplett [this message]
2012-08-31 19:54 ` Frederic Weisbecker
2012-08-31 21:38 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 03/26] rcu: Make RCU_FAST_NO_HZ handle adaptive ticks Paul E. McKenney
2012-08-31 23:40 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 04/26] rcu: Settle config for userspace extended quiescent state Paul E. McKenney
2012-08-31 23:44 ` Josh Triplett
2012-09-05 0:34 ` Paul E. McKenney
2012-09-05 0:46 ` Josh Triplett
2012-09-10 21:35 ` Frederic Weisbecker
2012-08-30 21:05 ` [PATCH tip/core/rcu 05/26] rcu: Allow rcu_user_enter()/exit() to nest Paul E. McKenney
2012-08-31 23:45 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 06/26] rcu: Ignore userspace extended quiescent state by default Paul E. McKenney
2012-08-31 23:46 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 07/26] rcu: Switch task's syscall hooks on context switch Paul E. McKenney
2012-08-31 23:48 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 08/26] x86: Syscall hooks for userspace RCU extended QS Paul E. McKenney
2012-08-31 23:59 ` Josh Triplett
2012-09-10 21:30 ` Frederic Weisbecker
2012-08-30 21:05 ` [PATCH tip/core/rcu 09/26] x86: Exception " Paul E. McKenney
2012-08-31 23:51 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 10/26] rcu: Exit RCU extended QS on kernel preemption after irq/exception Paul E. McKenney
2012-08-31 23:51 ` Josh Triplett
2012-09-06 16:52 ` Peter Zijlstra
2012-09-10 20:31 ` Frederic Weisbecker
2012-08-30 21:05 ` [PATCH tip/core/rcu 11/26] rcu: Exit RCU extended QS on user preemption Paul E. McKenney
2012-08-31 23:52 ` Josh Triplett
2012-09-06 17:02 ` Peter Zijlstra
2012-09-06 17:13 ` Peter Zijlstra
2012-09-10 20:26 ` Frederic Weisbecker
2012-09-12 9:33 ` Peter Zijlstra
2012-09-12 12:06 ` Frederic Weisbecker
2012-09-12 12:41 ` Peter Zijlstra
2012-09-12 12:52 ` Peter Zijlstra
2012-09-12 13:54 ` Frederic Weisbecker
2012-09-12 14:09 ` Peter Zijlstra
2012-09-12 13:52 ` Frederic Weisbecker
2012-09-12 15:21 ` Paul E. McKenney
2012-08-30 21:05 ` [PATCH tip/core/rcu 12/26] x86: Use the new schedule_user API on userspace preemption Paul E. McKenney
2012-08-31 23:53 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 13/26] x86: Exit RCU extended QS on notify resume Paul E. McKenney
2012-08-31 23:54 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 14/26] rcu: Userspace RCU extended QS selftest Paul E. McKenney
2012-08-31 23:54 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 15/26] alpha: Fix preemption handling in idle loop Paul E. McKenney
2012-08-31 23:55 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 16/26] alpha: Add missing RCU idle APIs on " Paul E. McKenney
2012-09-01 0:00 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 17/26] cris: " Paul E. McKenney
2012-09-01 0:01 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 18/26] frv: " Paul E. McKenney
2012-09-01 0:01 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 19/26] h8300: " Paul E. McKenney
2012-09-01 0:02 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 20/26] m32r: " Paul E. McKenney
2012-09-01 0:02 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 21/26] m68k: " Paul E. McKenney
2012-09-01 0:02 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 22/26] mn10300: " Paul E. McKenney
2012-09-01 0:03 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 23/26] parisc: " Paul E. McKenney
2012-09-01 0:03 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 24/26] score: " Paul E. McKenney
2012-09-01 0:04 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 25/26] xtensa: " Paul E. McKenney
2012-09-01 0:05 ` Josh Triplett
2012-08-30 21:05 ` [PATCH tip/core/rcu 26/26] ia64: " Paul E. McKenney
2012-09-01 0:05 ` Josh Triplett
2012-08-31 19:07 ` [PATCH tip/core/rcu 01/26] rcu: New rcu_user_enter() and rcu_user_exit() APIs Josh Triplett
2012-09-05 1:04 ` Paul E. McKenney
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