From 617294b2f33cec584f48c12d914fcc982f317be5 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 9 Nov 2020 23:32:39 +0100 Subject: [PATCH 069/323] genirq: Move prio assignment into the newly created thread Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.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 Signed-off-by: Thomas Gleixner [bigeasy: Patch description] Signed-off-by: Sebastian Andrzej Siewior Link: https://lkml.kernel.org/r/a23a826af7c108ea5651e73b8fbae5e653f16e86.camel@gmx.de Signed-off-by: Luis Claudio R. Goncalves --- kernel/irq/manage.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index 0159925054fa..5ec167fb77b9 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -1201,6 +1201,8 @@ static int irq_thread(void *data) irq_thread_set_ready(desc, action); + sched_set_fifo(current); + if (force_irqthreads && test_bit(IRQTF_FORCED_THREAD, &action->thread_flags)) handler_fn = irq_forced_thread_fn; @@ -1366,8 +1368,6 @@ setup_irq_thread(struct irqaction *new, unsigned int irq, bool secondary) 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 -- 2.43.0