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From: Frederic Weisbecker <frederic@kernel.org>
To: paulmck@kernel.org
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org
Subject: Re: [PATCH tip/core/rcu 06/10] softirq: Don't try waking ksoftirqd before it has been spawned
Date: Fri, 12 Mar 2021 12:36:41 +0100	[thread overview]
Message-ID: <20210312113641.GA3646@lothringen> (raw)
In-Reply-To: <20210304000019.22459-6-paulmck@kernel.org>

On Wed, Mar 03, 2021 at 04:00:15PM -0800, paulmck@kernel.org wrote:
> From: "Paul E. McKenney" <paulmck@kernel.org>
> 
> If there is heavy softirq activity, the softirq system will attempt
> to awaken ksoftirqd and will stop the traditional back-of-interrupt
> softirq processing.  This is all well and good, but only if the
> ksoftirqd kthreads already exist, which is not the case during early
> boot, in which case the system hangs.
> 
> One reproducer is as follows:
> 
> tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 2 --configs "TREE03" --kconfig "CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y CONFIG_NO_HZ_IDLE=y CONFIG_HZ_PERIODIC=n" --bootargs "threadirqs=1" --trust-make
> 
> This commit therefore adds a couple of existence checks for ksoftirqd
> and forces back-of-interrupt softirq processing when ksoftirqd does not
> yet exist.  With this change, the above test passes.
> 
> Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Reported-by: Uladzislau Rezki <urezki@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> [ paulmck: Remove unneeded check per Sebastian Siewior feedback. ]
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

  reply	other threads:[~2021-03-12 11:37 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-03 23:59 [PATCH tip/core/rcu 0/10] Miscellaneous fixes for v5.13 Paul E. McKenney
2021-03-04  0:00 ` [PATCH tip/core/rcu 01/10] rcu: Remove superfluous rdp fetch paulmck
2021-03-04  0:00 ` [PATCH tip/core/rcu 02/10] rcu: Fix CPU-offline trace in rcutree_dying_cpu paulmck
2021-03-04  0:00 ` [PATCH tip/core/rcu 03/10] rcu: Remove spurious instrumentation_end() in rcu_nmi_enter() paulmck
2021-03-04  0:00 ` [PATCH tip/core/rcu 04/10] rculist: Replace reference to atomic_ops.rst paulmck
2021-03-04  0:00 ` [PATCH tip/core/rcu 05/10] rcu: Fix kfree_rcu() docbook errors paulmck
2021-03-04  0:00 ` [PATCH tip/core/rcu 06/10] softirq: Don't try waking ksoftirqd before it has been spawned paulmck
2021-03-12 11:36   ` Frederic Weisbecker [this message]
2021-03-15 23:11     ` Paul E. McKenney
2021-03-04  0:00 ` [PATCH tip/core/rcu 07/10] rcu: Prevent dyntick-idle until ksoftirqd " paulmck
2021-03-11 23:23   ` Frederic Weisbecker
2021-03-11 23:34     ` Paul E. McKenney
2021-03-04  0:00 ` [PATCH tip/core/rcu 08/10] docs: Correctly spell Stephen Hemminger's name paulmck
2021-03-04  0:00 ` [PATCH tip/core/rcu 09/10] rcu: Add explicit barrier() to __rcu_read_unlock() paulmck
2021-03-04  0:00 ` [PATCH tip/core/rcu 10/10] rcu/tree: Add a trace event for RCU CPU stall warnings paulmck

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