• Paul Mackerras's avatar
    [POWERPC] Lazy interrupt disabling for 64-bit machines · d04c56f7
    Paul Mackerras authored
    This implements a lazy strategy for disabling interrupts.  This means
    that local_irq_disable() et al. just clear the 'interrupts are
    enabled' flag in the paca.  If an interrupt comes along, the interrupt
    entry code notices that interrupts are supposed to be disabled, and
    clears the EE bit in SRR1, clears the 'interrupts are hard-enabled'
    flag in the paca, and returns.  This means that interrupts only
    actually get disabled in the processor when an interrupt comes along.
    
    When interrupts are enabled by local_irq_enable() et al., the code
    sets the interrupts-enabled flag in the paca, and then checks whether
    interrupts got hard-disabled.  If so, it also sets the EE bit in the
    MSR to hard-enable the interrupts.
    
    This has the potential to improve performance, and also makes it
    easier to make a kernel that can boot on iSeries and on other 64-bit
    machines, since this lazy-disable strategy is very similar to the
    soft-disable strategy that iSeries already uses.
    
    This version renames paca->proc_enabled to paca->soft_enabled, and
    changes a couple of soft-disables in the kexec code to hard-disables,
    which should fix the crash that Michael Ellerman saw.  This doesn't
    yet use a reserved CR field for the soft_enabled and hard_enabled
    flags.  This applies on top of Stephen Rothwell's patches to make it
    possible to build a combined iSeries/other kernel.
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    d04c56f7
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