From: Peter Zijlstra <peterz@infradead.org>
To: gor@linux.ibm.com, jpoimboe@redhat.com, jikos@kernel.org,
mbenes@suse.cz, pmladek@suse.com, mingo@kernel.org
Cc: 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, paulmck@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 20:54:35 +0200 [thread overview]
Message-ID: <20210929185435.GW4323@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20210929152429.007420590@infradead.org>
On Wed, Sep 29, 2021 at 05:17:31PM +0200, Peter Zijlstra wrote:
> XXX I'm pretty sure I broke task-trace-rcu.
> -static noinstr void rcu_dynticks_eqs_enter(void)
> -{
> - int seq;
> -
> - /*
> - * CPUs seeing atomic_add_return() must see prior RCU read-side
> - * critical sections, and we also must force ordering with the
> - * next idle sojourn.
> - */
> - rcu_dynticks_task_trace_enter(); // Before ->dynticks update!
> - seq = rcu_dynticks_inc(1);
> - // RCU is no longer watching. Better be in extended quiescent state!
> - WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & 0x1));
> -}
> -static noinstr void rcu_dynticks_eqs_exit(void)
> -{
> - int seq;
> -
> - /*
> - * CPUs seeing atomic_add_return() must see prior idle sojourns,
> - * and we also must force ordering with the next RCU read-side
> - * critical section.
> - */
> - seq = rcu_dynticks_inc(1);
> - // RCU is now watching. Better not be in an extended quiescent state!
> - rcu_dynticks_task_trace_exit(); // After ->dynticks update!
> - WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & 0x1));
> -}
So specifically rcu_dynticks_task_trace_{enter,exit}() are now orphaned.
After this patch, nothing calls them.
However, looking at this again, we've got:
__context_tracking_enter()
rcu_user_enter()
rcu_eqs_enter()
rcu_dynticks_eqs_enter()
rcu_dynticks_task_trace_enter()
rcu_dynticks_inc();
rcu_dynticks_task_enter();
ct_seq_user_enter()
atomic_add_return()
and on the other end:
__context_tracking_exit()
ct_seq_user_exit()
atomic_add_return()
rcu_user_exit()
rcu_esq_exit()
rcu_dynticks_task_exit()
rcu_dynticks_eqs_exit()
rcu_dynticks_inc()
rcu_dynticks_task_trace_exit()
And since we want to replace dynticks_inc() with ct_seq_*() the
rcu_dynticks_task_{enter,exit}() ought to be pulled before that..
Instead I orphaned rcu_dynticks_task_trace_{enter,exit}() which should
more or less stay where they are.
I seems to have confused the two :/
next prev parent reply other threads:[~2021-09-29 18:55 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
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 [this message]
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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