From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com,
oleg@redhat.com, Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH tip/core/rcu 06/10] trace: Eliminate cond_resched_rcu_qs() in favor of cond_resched()
Date: Sun, 25 Feb 2018 21:47:27 -0800 [thread overview]
Message-ID: <20180226054727.GJ2855@linux.vnet.ibm.com> (raw)
In-Reply-To: <20180225235748.4ce882e5@vmware.local.home>
On Sun, Feb 25, 2018 at 11:57:48PM -0500, Steven Rostedt wrote:
> On Sun, 25 Feb 2018 10:17:30 -0800
> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
>
>
> > And probably not. You are probably running CONFIG_PREEMPT=y (otherwise
> > RCU-tasks is trivial), so cond_resched() is a complete no-op:
> >
> > static inline int _cond_resched(void) { return 0; }
> >
> > I could make this call rcu_all_qs(), but I would not expect Peter Zijlstra
> > to be at all happy with that sort of change.
> >
> > And the people who asked for the cond_resched() work probably aren't
> > going to be happy with the resumed proliferation of cond_resched_rcu_qs().
> >
> > Hmmm... Grasping at straws... Could we make cond_resched() be something
> > like a tracepoint and instrument them with cond_resched_rcu_qs() if the
> > current RCU-tasks grace period ran for more that (say) a minute of its
> > ten-minute stall-warning span?
> >
>
> Instead of monkeying with cond_resched(), since this is "special" code,
> why don't I just have that code call it directly?
>
> cond_resched();
> rcu_note_voluntary_context_switch(current);
The advantage of the last patch that I sent is that the special call
is in one place. (This is the one that adds the "special" definition
for _cond_resched().)
Thanx, Paul
next prev parent reply other threads:[~2018-02-26 5:47 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-01 19:21 [PATCH tip/core/rcu 0/10] Don not IPI offline CPUs, de-emphasize cond_resched_rcu_qs() Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 01/10] sched: Stop resched_cpu() from sending IPIs to offline CPUs Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 02/10] sched: Stop switched_to_rt() " Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 03/10] netfilter: Eliminate cond_resched_rcu_qs() in favor of cond_resched() Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 04/10] mm: " Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 05/10] workqueue: " Paul E. McKenney
2017-12-02 1:06 ` Lai Jiangshan
2017-12-04 18:28 ` Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 06/10] trace: " Paul E. McKenney
2018-02-24 20:12 ` Steven Rostedt
2018-02-25 17:49 ` Paul E. McKenney
2018-02-25 18:17 ` Paul E. McKenney
2018-02-25 18:39 ` Paul E. McKenney
2018-02-27 2:29 ` Steven Rostedt
2018-02-27 15:36 ` Paul E. McKenney
2018-02-28 23:12 ` Steven Rostedt
2018-03-01 1:21 ` Paul E. McKenney
2018-03-01 5:04 ` Steven Rostedt
2018-03-01 20:48 ` Paul E. McKenney
2018-03-02 20:06 ` Steven Rostedt
2018-03-03 0:54 ` Paul E. McKenney
2018-02-26 4:57 ` Steven Rostedt
2018-02-26 5:47 ` Paul E. McKenney [this message]
2017-12-01 19:21 ` [PATCH tip/core/rcu 07/10] softirq: " Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 08/10] fs: " Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 09/10] doc: " Paul E. McKenney
2017-12-01 19:21 ` [PATCH tip/core/rcu 10/10] rcu: Account for rcu_all_qs() in cond_resched() Paul E. McKenney
2017-12-02 8:56 ` Peter Zijlstra
2017-12-02 12:22 ` Paul E. McKenney
2017-12-02 13:55 ` Peter Zijlstra
2018-02-24 20:18 ` Steven Rostedt
2018-02-25 17:52 ` Paul E. McKenney
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