Jean-Francois Dagenais reported:
Configuring a gpio pin with the gpio-pch driver with
"IRQF_TRIGGER_LOW | IRQF_ONESHOT" generates an interrupt storm for
threaded ISR until the ISR thread actually gets to physically clear
the interrupt on the triggering chip!! The immediate observable
symptom is the high CPU usage for my ISR thread task and the
interrupt count in /proc/interrupts incrementing radically.
The driver is wrong in several ways:
1) Using handle_simple_irq() does not provide proper flow control
handling. In the case of oneshot threaded handlers for the
demultiplexed interrupts this results in an interrupt storm because
the simple handler does not deal with masking/unmasking. Even
without threaded oneshot handlers an interrupt storm for level type
interrupts can easily be triggered when the interrupt is disabled
and the interrupt line is activated from the device.
2) Acknowlegding the demultiplexed interrupt before calling the
handler is wrong for level type interrupts.
3) The set_type function unconditionally enables the interrupt. It's
supposed to set the type and nothing else. The unmasking is done by
the core code.
Move the acknowledge code into a separate function and add it to the
demux irqchip callbacks.
Remove the unconditional enabling from the set_type() callback and set
the proper flow handlers depending on the selected type (level/edge).
Reported-and-tested-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
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