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Fix race in gpio_set_irq_enabled_with_callback #2635

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Fix race in gpio_set_irq_enabled_with_callback #2635

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6 changes: 4 additions & 2 deletions src/rp2_common/hardware_gpio/gpio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -196,9 +196,11 @@ void gpio_set_irq_enabled(uint gpio, uint32_t events, bool enabled) {
}

void gpio_set_irq_enabled_with_callback(uint gpio, uint32_t events, bool enabled, gpio_irq_callback_t callback) {
// first set callback, then enable the interrupt
gpio_set_irq_callback(callback);
// when enabling, first set callback, then enable the interrupt
// when disabling, first disable the interrupt, then clear callback
if (enabled) gpio_set_irq_callback(callback);
gpio_set_irq_enabled(gpio, events, enabled);
if (!enabled) gpio_set_irq_callback(callback);
if (enabled) irq_set_enabled(IO_IRQ_BANK0, true);
Comment on lines +199 to 204
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Is this function likely to get used in performance-critical code? If it is, perhaps it's worth reducing the branches? 🤔 (or is one of those cases where the compiler is able to do this optimisation automatically?)

Suggested change
// when enabling, first set callback, then enable the interrupt
// when disabling, first disable the interrupt, then clear callback
if (enabled) gpio_set_irq_callback(callback);
gpio_set_irq_enabled(gpio, events, enabled);
if (!enabled) gpio_set_irq_callback(callback);
if (enabled) irq_set_enabled(IO_IRQ_BANK0, true);
// when enabling, first set callback, then enable the interrupt
// when disabling, first disable the interrupt, then clear callback
if (enabled) {
gpio_set_irq_callback(callback);
gpio_set_irq_enabled(gpio, events, enabled);
irq_set_enabled(IO_IRQ_BANK0, true);
} else {
gpio_set_irq_enabled(gpio, events, enabled);
gpio_set_irq_callback(callback);
}

}

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