On Fri, Dec 04 2020 at 21:19, Oleksandr Natalenko wrote:
> On Thu, Dec 03, 2020 at 07:04:00PM +0000, bugzilla-dae...@bugzilla.kernel.org
> wrote:
>> 2) Have a wrapper around handle_generic_irq() which ensures that
>> interrupts are disabled before invoking it.
> The question is whether it's guaranteed under all circumstances
> including forced irq threading. The i801 driver has assumptions about
> this, so I wouldn't be surprised if there are more.
Assuming that a final answer might take some time, the below which
implements #2 will make it at least work for now.
Thanks,
tglx
---
Subject: genirq, i2c: Provide and use generic_dispatch_irq()
From: Thomas Gleixner <t...@linutronix.de>
Date: Thu, 03 Dec 2020 19:12:24 +0100
Carlos reported that on his system booting with 'threadirqs' on the command
line result in the following warning:
irq 31 handler irq_default_primary_handler+0x0/0x10 enabled interrupts
WARNING: CPU: 2 PID: 989 at kernel/irq/handle.c:153
__handle_irq_event_percpu+0x19f/0x1b0
The reason is in the i2c stack:
i801_isr()
i801_host_notify_isr()
i2c_handle_smbus_host_notify()
generic_handle_irq()
and that explodes with forced interrupt threading because it's called with
interrupts enabled.
It would be possible to set IRQF_NO_THREAD on the i801 interrupt to exclude
it from force threading, but that would break on RT and require a larger
update.
It's also unclear whether there are other drivers which can reach that code
path via i2c_slave_host_notify_cb(). As there are enough i2c drivers which
use threaded interrupt handlers by default it seems not completely
impossible that this can happen even without force threaded interrupts.
For a quick fix provide a wrapper around generic_handle_irq() which has a
local_irq_save/restore() around the invocation and use it in the i2c code.
Reported-by: Carlos Jimenez <javashin1...@gmail.com>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202453
---
drivers/i2c/i2c-core-base.c | 2 +-
include/linux/irqdesc.h | 1 +
kernel/irq/irqdesc.c | 20 ++++++++++++++++++++
3 files changed, 22 insertions(+), 1 deletion(-)
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1385,7 +1385,7 @@ int i2c_handle_smbus_host_notify(struct
if (irq <= 0)
return -ENXIO;
- generic_handle_irq(irq);
+ generic_dispatch_irq(irq);
return 0;
}
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -153,6 +153,7 @@ static inline void generic_handle_irq_de
}
int generic_handle_irq(unsigned int irq);
+int generic_dispatch_irq(unsigned int irq);
#ifdef CONFIG_HANDLE_DOMAIN_IRQ
/*
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -652,6 +652,26 @@ int generic_handle_irq(unsigned int irq)
}
EXPORT_SYMBOL_GPL(generic_handle_irq);
+/**
+ * generic_dispatch_irq - Dispatch an interrupt from an interrupt handler
+ * @irq: The irq number to handle
+ *
+ * A wrapper around generic_handle_irq() which ensures that interrupts are
+ * disabled when the primary handler of the dispatched irq is invoked.
+ * This is useful for interrupt handlers with dispatching to be safe for
+ * the forced threaded case.
+ */
+int generic_dispatch_irq(unsigned int irq)
+{
+ unsigned long flags;
+ int ret;
+
+ local_irq_save(&flags);
+ ret = generic_handle_irq(irq);
+ local_irq_restore(&flags);
+ return ret;
+}
+
#ifdef CONFIG_HANDLE_DOMAIN_IRQ
/**
* __handle_domain_irq - Invoke the handler for a HW irq belonging to a domain
