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Message-ID: <20210924094755.2m32pgqwrqw2cg2s@linutronix.de>
Date: Fri, 24 Sep 2021 11:47:55 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] smp: Wake ksoftirqd on PREEMPT_RT instead do_softirq().
The softirq implementation on PREEMPT_RT does not provide do_softirq().
The other user of do_softirq() is replaced with a local_bh_disable()
+ enable() around the possible raise-softirq invocation. This can not be
done here because migration_cpu_stop() is invoked with disabled
preemption.
Wake the softirq thread on PREEMPT_RT if there are any pending softirqs.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
kernel/smp.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
---
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -690,10 +690,21 @@ void flush_smp_call_function_from_idle(v
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->idle, CFD_SEQ_NOCPU,
smp_processor_id(), CFD_SEQ_IDLE);
+
local_irq_save(flags);
flush_smp_call_function_queue(true);
- if (local_softirq_pending())
- do_softirq();
+
+ if (local_softirq_pending()) {
+
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ do_softirq();
+ } else {
+ struct task_struct *ksoftirqd = this_cpu_ksoftirqd();
+
+ if (ksoftirqd && !task_is_running(ksoftirqd))
+ wake_up_process(ksoftirqd);
+ }
+ }
local_irq_restore(flags);
}
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