From: Lars-Peter Clausen <lars@metafoo.de>
To: Christian Eggers <ceggers@arri.de>
Cc: Jonathan Cameron <jic23@kernel.org>,
stable@vger.kernel.org, Hartmut Knaack <knaack.h@gmx.de>,
Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iio: trigger: sysfs: Disable irqs before calling iio_trigger_poll()
Date: Mon, 3 Aug 2020 08:52:54 +0200 [thread overview]
Message-ID: <a59d204e-aeb0-2649-5e6f-f07815713d1a@metafoo.de> (raw)
In-Reply-To: <4871626.01MspNxQH7@n95hx1g2>
On 8/3/20 8:44 AM, Christian Eggers wrote:
> Hi Lars,
>
> On Monday, 3 August 2020, 08:37:43 CEST, Lars-Peter Clausen wrote:
>> The sysfs IIO trigger uses irq_work to schedule the iio_trigger_poll()
>> and the promise of irq_work is that the callback will run in hard IRQ
>> context. That's the whole point of it.
>>
>> irq_work_run_list(), which shows up in your callgraph, has as
>> BUG_ON(!irqs_disabled())[1], so we should never even get to calling
>> iio_trigger_poll() if IRQs where not disabled at this point. That's the
>> same condition that triggers the WARN_ON() in __handle_irq_event_percpu.
> is my patch sufficient, or would you prefer a different solution?
The code in normal upstream is correct, there is no need to patch it
since iio_sysfs_trigger_work() always runs with IRQs disabled.
>
>> Are you using a non-upstream kernel? Maybe a RT kernel?
> I use v5.4.<almost-latest>-rt
That explains it. Have a look at
0200-irqwork-push-most-work-into-softirq-context.patch.
The right fix for this issue is to add the following snippet to the RT
patchset.
diff --git a/drivers/iio/trigger/iio-trig-sysfs.c
b/drivers/iio/trigger/iio-trig-sysfs.c
--- a/drivers/iio/trigger/iio-trig-sysfs.c
+++ b/drivers/iio/trigger/iio-trig-sysfs.c
@@ -161,6 +161,7 @@ static int iio_sysfs_trigger_probe(int id)
iio_trigger_set_drvdata(t->trig, t);
init_irq_work(&t->work, iio_sysfs_trigger_work);
+ t->work.flags = IRQ_WORK_HARD_IRQ;
ret = iio_trigger_register(t->trig);
if (ret)
next prev parent reply other threads:[~2020-08-03 6:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 14:57 [PATCH] iio: trigger: sysfs: Disable irqs before calling iio_trigger_poll() Christian Eggers
2020-08-01 16:02 ` Jonathan Cameron
2020-08-02 15:05 ` Lars-Peter Clausen
2020-08-03 5:16 ` Christian Eggers
2020-08-03 6:37 ` Lars-Peter Clausen
2020-08-03 6:44 ` Christian Eggers
2020-08-03 6:52 ` Lars-Peter Clausen [this message]
2020-08-12 11:01 ` Christian Eggers
2020-08-13 7:23 ` Lars-Peter Clausen
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