-rt doesnt wrap cli/sti anymore: spin_lock_irq*() doesnt disable irq
flags on -rt, thus the amount of real irqs-off sections is very small
and reviewable.
But nevertheless an incarnation of the code survived and is upstream
already, in the form of TRACE_IRQFLAGS lockdep code ;) This implements a
soft hardirq flag _today_: all that would be needed is for Xen to define
raw_local_irq_disable() as a NOP, and to use the
current->hardirqs_enabled as 'soft IRQ-off flag'.
Note that ->hardirqs_enabled is self-maintained, i.e. it's not just a
stupid shadow of the hardirq flag, it's an independently maintained flag
that does not rely on the existence of the hard flag.
[ this code even has its own debugging code, so out-of-sync-flags,
double-off and double-on is detected and complained about. So all the
hard stuff has already been done as part of lockdep, and it's even
long-term maintainable because under a native lockdep kernel we check
the soft flag against the hard flag. ]
so i think a soft cli/sti flag support should be merged/unified with the
trace_hardirqs_on()/trace_hardirqs_off() code.
Ingo
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