From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: gor@linux.ibm.com, jpoimboe@redhat.com, jikos@kernel.org,
mbenes@suse.cz, pmladek@suse.com, mingo@kernel.org,
linux-kernel@vger.kernel.org, joe.lawrence@redhat.com,
fweisbec@gmail.com, tglx@linutronix.de, hca@linux.ibm.com,
svens@linux.ibm.com, sumanthk@linux.ibm.com,
live-patching@vger.kernel.org, rostedt@goodmis.org,
x86@kernel.org
Subject: Re: [RFC][PATCH v2 08/11] context_tracking,rcu: Replace RCU dynticks counter with context_tracking
Date: Wed, 29 Sep 2021 21:09:35 +0200 [thread overview]
Message-ID: <20210929190935.GX4323@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20210929183701.GY880162@paulmck-ThinkPad-P17-Gen-1>
On Wed, Sep 29, 2021 at 11:37:01AM -0700, Paul E. McKenney wrote:
> On Wed, Sep 29, 2021 at 05:17:31PM +0200, Peter Zijlstra wrote:
> The CT_SEQ_WORK bit means neither idle nor nohz_full user, correct?
That bit is indeed independent, it can get set remotely by cmpxchg when
in user/eqs state and will be tested and (eventually) cleared when
leaving user/eqs state.
> So let's see if I intuited the decoder ring, where "kernel" means that
> portion of the kernel that is non-noinstr...
>
> CT_SEQ_WORK CT_SEQ_NMI CT_SEQ_USER Description?
> 0 0 0 Idle or non-nohz_full user
> 0 0 1 nohz_full user
> 0 1 0 NMI from 0,0,0
> 0 1 1 NMI from 0,0,1
> 1 0 0 Non-idle kernel
> 1 0 1 Cannot happen?
> 1 1 0 NMI from 1,0,1
> 1 1 1 NMI from cannot happen
>
> And of course if a state cannot happen, Murphy says that you will take
> an NMI in that state.
Urgh, you have the bits the 'wrong' way around :-)
MSB 3210
|-------||||
Where [MSB-3] is the actual sequence number, [21] is the state and [0]
is the work-pending bit.
The table for [21] is like:
USER NMI
0 0 kernel
0 1 kernel took nmi
1 0 user
1 1 user took nmi
So effectively EQS is 10 only, the other 3 states are kernel.
next prev parent reply other threads:[~2021-09-29 19:12 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-29 15:17 [PATCH v2 00/11] sched,rcu,context_tracking,livepatch: Improve livepatch task transitions for idle and NOHZ_FULL Peter Zijlstra
2021-09-29 15:17 ` [PATCH v2 01/11] sched: Improve try_invoke_on_locked_down_task() Peter Zijlstra
2021-09-29 15:17 ` [PATCH v2 02/11] sched,rcu: Rework try_invoke_on_locked_down_task() Peter Zijlstra
2021-09-29 15:17 ` [PATCH v2 03/11] sched,livepatch: Use task_call_func() Peter Zijlstra
2021-10-05 11:40 ` Petr Mladek
2021-10-05 14:03 ` Peter Zijlstra
2021-10-06 8:59 ` Miroslav Benes
2021-09-29 15:17 ` [PATCH v2 04/11] sched: Simplify wake_up_*idle*() Peter Zijlstra
2021-10-13 14:32 ` Qian Cai
2021-10-19 3:47 ` Qian Cai
2021-10-19 8:56 ` Peter Zijlstra
2021-10-19 9:10 ` Peter Zijlstra
2021-10-19 15:32 ` Qian Cai
2021-10-19 15:50 ` Peter Zijlstra
2021-10-19 19:22 ` Qian Cai
2021-10-19 20:27 ` Peter Zijlstra
[not found] ` <CGME20211022134630eucas1p2e79e2816587d182c580459d567c1f2a9@eucas1p2.samsung.com>
2021-10-22 13:46 ` Marek Szyprowski
2021-09-29 15:17 ` [PATCH v2 05/11] sched,livepatch: Use wake_up_if_idle() Peter Zijlstra
2021-10-05 12:00 ` Petr Mladek
2021-10-06 9:16 ` Miroslav Benes
2021-10-07 9:18 ` Vasily Gorbik
2021-10-07 10:02 ` Peter Zijlstra
2021-10-13 19:37 ` Arnd Bergmann
2021-10-14 10:42 ` Peter Zijlstra
2021-09-29 15:17 ` [RFC][PATCH v2 06/11] context_tracking: Prefix user_{enter,exit}*() Peter Zijlstra
2021-09-29 15:17 ` [RFC][PATCH v2 07/11] context_tracking: Add an atomic sequence/state count Peter Zijlstra
2021-09-29 15:17 ` [RFC][PATCH v2 08/11] context_tracking,rcu: Replace RCU dynticks counter with context_tracking Peter Zijlstra
2021-09-29 18:37 ` Paul E. McKenney
2021-09-29 19:09 ` Peter Zijlstra [this message]
2021-09-29 19:11 ` Peter Zijlstra
2021-09-29 19:13 ` Peter Zijlstra
2021-09-29 19:24 ` Peter Zijlstra
2021-09-29 19:45 ` Paul E. McKenney
2021-09-29 18:54 ` Peter Zijlstra
2021-09-29 15:17 ` [RFC][PATCH v2 09/11] context_tracking,livepatch: Dont disturb NOHZ_FULL Peter Zijlstra
2021-10-06 8:12 ` Petr Mladek
2021-10-06 9:04 ` Peter Zijlstra
2021-10-06 10:29 ` Petr Mladek
2021-10-06 11:41 ` Peter Zijlstra
2021-10-06 11:48 ` Miroslav Benes
2021-09-29 15:17 ` [RFC][PATCH v2 10/11] livepatch: Remove klp_synchronize_transition() Peter Zijlstra
2021-10-06 12:30 ` Petr Mladek
2021-09-29 15:17 ` [RFC][PATCH v2 11/11] context_tracking,x86: Fix text_poke_sync() vs NOHZ_FULL Peter Zijlstra
2021-10-21 18:39 ` Marcelo Tosatti
2021-10-21 18:40 ` Marcelo Tosatti
2021-10-21 19:25 ` Peter Zijlstra
2021-10-21 19:57 ` Marcelo Tosatti
2021-10-21 20:18 ` Peter Zijlstra
2021-10-26 18:19 ` Marcelo Tosatti
2021-10-26 19:38 ` Peter Zijlstra
2021-09-29 18:03 ` [PATCH v2 00/11] sched,rcu,context_tracking,livepatch: Improve livepatch task transitions for idle and NOHZ_FULL Paul E. McKenney
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