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authorThomas Gleixner <tglx@linutronix.de>2021-03-17 15:38:52 +0100
committerThomas Gleixner <tglx@linutronix.de>2021-03-21 00:17:52 +0100
commit81e2073c175b887398e5bca6c004efa89983f58d (patch)
tree67aa8a85a9e28345230493605c2465c21b870860
parentef4cb70a4c22bf301cd757dcc838dc8ca9526477 (diff)
downloadlinux-stericsson-81e2073c175b887398e5bca6c004efa89983f58d.tar.gz
genirq: Disable interrupts for force threaded handlers
With interrupt force threading all device interrupt handlers are invoked from kernel threads. Contrary to hard interrupt context the invocation only disables bottom halfs, but not interrupts. This was an oversight back then because any code like this will have an issue: thread(irq_A) irq_handler(A) spin_lock(&foo->lock); interrupt(irq_B) irq_handler(B) spin_lock(&foo->lock); This has been triggered with networking (NAPI vs. hrtimers) and console drivers where printk() happens from an interrupt which interrupted the force threaded handler. Now people noticed and started to change the spin_lock() in the handler to spin_lock_irqsave() which affects performance or add IRQF_NOTHREAD to the interrupt request which in turn breaks RT. Fix the root cause and not the symptom and disable interrupts before invoking the force threaded handler which preserves the regular semantics and the usefulness of the interrupt force threading as a general debugging tool. For not RT this is not changing much, except that during the execution of the threaded handler interrupts are delayed until the handler returns. Vs. scheduling and softirq processing there is no difference. For RT kernels there is no issue. Fixes: 8d32a307e4fa ("genirq: Provide forced interrupt threading") Reported-by: Johan Hovold <johan@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Johan Hovold <johan@kernel.org> Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Link: https://lore.kernel.org/r/20210317143859.513307808@linutronix.de
-rw-r--r--kernel/irq/manage.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index dec3f73e8db9..21ea370fccda 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1142,11 +1142,15 @@ irq_forced_thread_fn(struct irq_desc *desc, struct irqaction *action)
irqreturn_t ret;
local_bh_disable();
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ local_irq_disable();
ret = action->thread_fn(action->irq, action->dev_id);
if (ret == IRQ_HANDLED)
atomic_inc(&desc->threads_handled);
irq_finalize_oneshot(desc, action);
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ local_irq_enable();
local_bh_enable();
return ret;
}