From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: 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,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 06/10] softirq: Don't try waking ksoftirqd before it has been spawned
Date: Wed, 3 Mar 2021 16:00:15 -0800 [thread overview]
Message-ID: <20210304000019.22459-6-paulmck@kernel.org> (raw)
In-Reply-To: <20210303235958.GA22373@paulmck-ThinkPad-P72>
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>
---
kernel/softirq.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 9908ec4a..bad14ca 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -211,7 +211,7 @@ static inline void invoke_softirq(void)
if (ksoftirqd_running(local_softirq_pending()))
return;
- if (!force_irqthreads) {
+ if (!force_irqthreads || !__this_cpu_read(ksoftirqd)) {
#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
/*
* We can safely execute softirq on the current stack if
--
2.9.5
next prev parent reply other threads:[~2021-03-04 0:17 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 ` paulmck [this message]
2021-03-12 11:36 ` [PATCH tip/core/rcu 06/10] softirq: Don't try waking ksoftirqd before it has been spawned Frederic Weisbecker
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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