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From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 9 Nov 2020 23:32:39 +0100
Subject: [PATCH 2/2] genirq: Move prio assignment into the newly created
thread
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.17-rt32.tar.xz
With enabled threaded interrupts the nouveau driver reported the
following:
| Chain exists of:
| &mm->mmap_lock#2 --> &device->mutex --> &cpuset_rwsem
|
| Possible unsafe locking scenario:
|
| CPU0 CPU1
| ---- ----
| lock(&cpuset_rwsem);
| lock(&device->mutex);
| lock(&cpuset_rwsem);
| lock(&mm->mmap_lock#2);
The device->mutex is nvkm_device::mutex.
Unblocking the lockchain at `cpuset_rwsem' is probably the easiest thing
to do.
Move the priority assignment to the start of the newly created thread.
Fixes: 710da3c8ea7df ("sched/core: Prevent race condition between cpuset and __sched_setscheduler()")
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy: Patch description]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lkml.kernel.org/r/a23a826af7c108ea5651e73b8fbae5e653f16e86.camel@gmx.de
---
kernel/irq/manage.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1155,6 +1155,8 @@ static int irq_thread(void *data)
irqreturn_t (*handler_fn)(struct irq_desc *desc,
struct irqaction *action);
+ sched_set_fifo(current);
+
if (force_irqthreads && test_bit(IRQTF_FORCED_THREAD,
&action->thread_flags))
handler_fn = irq_forced_thread_fn;
@@ -1320,8 +1322,6 @@ setup_irq_thread(struct irqaction *new,
if (IS_ERR(t))
return PTR_ERR(t);
- sched_set_fifo(t);
-
/*
* We keep the reference to the task struct even if
* the thread dies to avoid that the interrupt code
|
