NestedInterruptTplLib relies on CPU interrupts being disabled to
guarantee exclusive (and hence atomic) access to the shared state in
IsrState. Nothing in the calling interrupt handler should have
re-enabled interrupts before calling NestedInterruptRestoreTPL(), and
the loop in NestedInterruptRestoreTPL() itself maintains the invariant
that interrupts are disabled at the start of each iteration.
Add assertions to clarify this invariant, and expand the comments
around the calls to RestoreTPL() and DisableInterrupts() to clarify
the expectations around enabling and disabling interrupts.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>
ae0be176a8