Interrupt protection
Disabling interrupts in the CPU
The local_irq_save() and local_irq_disable() helpers are no more
disabling interrupts in the CPU when interrupt pipelining is enabled,
but only disable interrupt events virtually for the in-band
stage.
A set of helpers is provided for manipulating the interrupt disable
flag in the CPU instead. When CONFIG_IRQ_PIPELINE is disabled, this
set maps 1:1 over the regular local_irq_*() API.
| Original/Virtual | Non-virtualized call |
|---|---|
| local_save_flags(flags) | flags = hard_local_save_flags() |
| local_irq_disable() | hard_local_irq_disable() |
| local_irq_enable() | hard_local_irq_enable() |
| local_irq_save(flags) | flags = hard_local_irq_save() |
| local_irq_restore(flags) | hard_local_irq_restore(flags) |
| irqs_disabled() | hard_irqs_disabled() |
| irqs_disabled_flags(flags) | hard_irqs_disabled_flags(flags) |
Stalling the out-of-band stage
Just like the in-band stage is affected by the state of the virtual interrupt disable flag, the interrupt state of the oob stage is controlled by a dedicated stall bit flag in the oob stage’s status. In combination with the interrupt disable bit in the CPU, this software bit controls interrupt delivery to the oob stage.
When this stall bit is set, interrupts which might be pending in the oob stage’s event log of the current CPU are not played. Conversely, the out-of-band handlers attached to pending IRQs are fired when the stall bit is clear. The following table represents the equivalent calls affecting the stall bit for each stage:
| In-band stage operation | OOB stage operation |
|---|---|
| local_save_flags(flags) | -none- |
| local_irq_disable() | oob_irq_disable() |
| local_irq_enable() | oob_irq_enable() |
| local_irq_save(flags) | flags = oob_irq_save() |
| local_irq_restore(flags) | oob_irq_restore(flags) |
| irqs_disabled() | oob_irqs_disabled() |
| irqs_disabled_flags(flags) | -none- |
