From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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, rostedt@goodmis.org,
dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com,
fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH tip/core/rcu 03/13] rcu: Stop treating in-kernel CPU-bound workloads as errors
Date: Thu, 25 Feb 2016 10:43:17 +0100 [thread overview]
Message-ID: <20160225094317.GN6356@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1456290770-18659-3-git-send-email-paulmck@linux.vnet.ibm.com>
On Tue, Feb 23, 2016 at 09:12:40PM -0800, Paul E. McKenney wrote:
> Commit 4a81e8328d379 ("Reduce overhead of cond_resched() checks for RCU")
> handles the error case where a nohz_full loops indefinitely in the kernel
> with the scheduling-clock interrupt disabled. However, this handling
> includes IPIing the CPU running the offending loop, which is not what
> we want for real-time workloads. And there are starting to be real-time
> CPU-bound in-kernel workloads, and these must be handled without IPIing
> the CPU, at least not in the common case. Therefore, this situation can
> no longer be dismissed as an error case.
Do explain. Doing "for (;;) ;" in a kernel RT thread is just as bad for
general system health as is doing the same in userspace.
Also, who runs his RT workload in-kernel ?
next prev parent reply other threads:[~2016-02-25 9:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-24 5:12 [PATCH tip/core/rcu 0/13] Miscellaneous fixes for 4.6 Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 01/13] rcu: Assign false instead of 0 for ->core_needs_qs Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 02/13] rcu: Update rcu_report_qs_rsp() comment Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 03/13] rcu: Stop treating in-kernel CPU-bound workloads as errors Paul E. McKenney
2016-02-25 9:43 ` Peter Zijlstra [this message]
2016-02-25 17:20 ` Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 04/13] rcu: Set rdp->gpwrap when CPU is idle Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 05/13] rcutorture: Correct no-expedite console messages Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 06/13] rcu: Remove useless rcu_data_p when !PREEMPT_RCU Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 07/13] sparse: Add __private to privatize members of structs Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 08/13] RCU: Privatize rcu_node::lock Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 09/13] irq: Privatize irq_common_data::state_use_accessors Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 10/13] rcu: Make rcu/tiny_plugin.h explicitly non-modular Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 11/13] rcu: Document unique-name limitation for DEFINE_STATIC_SRCU() Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 12/13] rcu: Catch up rcu_report_qs_rdp() comment with reality Paul E. McKenney
2016-02-24 5:12 ` [PATCH tip/core/rcu 13/13] rcu: Remove rcu_user_hooks_switch Paul E. McKenney
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