Daniel Kobras writes:
> I'd like to know the terms under which saving and restoring processor
> flags can be omitted? In other words, how can I determine if I have to use
> spin_lock_irqsave or if spin_lock_irq is sufficient? I had a look into
> Documentation/spinlocks.txt, but unfortunately the _irq/_bh variants
> aren't even mentioned.
Basically, if you can guarantee that at the point when spin_lock_irq()
is called, interrupts will always be enabled, then you can use
spin_lock_irq() instead of spin_lock_irqsave().
The reason for this is that you know that interrupts were enabled, so
when you come out of your critical region, you can just re-enable them
with spin_unlock_irq().
_____
|_____| ------------------------------------------------- ---+---+-
| | Russell King rmk@arm.linux.org.uk --- ---
| | | | http://www.arm.linux.org.uk/~rmk/aboutme.html / / |
| +-+-+ --- -+-
/ | THE developer of ARM Linux |+| /|\
/ | | | --- |
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