From 4c2680de43867f05f3d2dbeee5b48549682293fa Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 10 Nov 2020 12:38:48 +0100
Subject: [PATCH 019/158] genirq: Move prio assignment into the newly created
thread
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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/a23a826af7c108ea5651e73b8fbae5e653f16e86.camel@gmx.de
---
kernel/irq/manage.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
Index: linux-5.15.19-rt29/kernel/irq/manage.c
===================================================================
@ linux-5.15.19-rt29/kernel/irq/manage.c:1262 @ 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;
@ linux-5.15.19-rt29/kernel/irq/manage.c:1429 @ 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