From: Thomas Gleixner Date: Tue, 10 Nov 2020 11:38:48 +0000 (+0100) Subject: genirq: Move prio assignment into the newly created thread X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e739f98b4b11337a4e3865364b8922a9e5ad32b6;p=linux.git 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 Signed-off-by: Thomas Gleixner [bigeasy: Patch description] Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/a23a826af7c108ea5651e73b8fbae5e653f16e86.camel@gmx.de --- diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index b39248325541d..7405e384e5ed0 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -1259,6 +1259,8 @@ 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; @@ -1424,8 +1426,6 @@ 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