• Paul Mackerras's avatar
    powerpc/perf_event: Reduce latency of calling perf_event_do_pending · b0d278b7
    Paul Mackerras authored
    Commit 0fe1ac48 ("powerpc/perf_event: Fix oops due to
    perf_event_do_pending call") moved the call to perf_event_do_pending
    in timer_interrupt() down so that it was after the irq_enter() call.
    Unfortunately this moved it after the code that checks whether it
    is time for the next decrementer clock event.  The result is that
    the call to perf_event_do_pending() won't happen until the next
    decrementer clock event is due.  This was pointed out by Milton
    Miller.
    
    This fixes it by moving the check for whether it's time for the
    next decrementer clock event down to the point where we're about
    to call the event handler, after we've called perf_event_do_pending.
    
    This has the side effect that on old pre-Core99 Powermacs where we
    use the ppc_n_lost_interrupts mechanism to replay interrupts, a
    replayed interrupt will incur a little more latency since it will
    now do the code from the irq_enter down to the irq_exit, that it
    used to skip.  However, these machines are now old and rare enough
    that this doesn't matter.  To make it clear that ppc_n_lost_interrupts
    is only used on Powermacs, and to speed up the code slightly on
    non-Powermac ppc32 machines, the code that tests ppc_n_lost_interrupts
    is now conditional on CONFIG_PMAC as well as CONFIG_PPC32.
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    Cc: stable@kernel.org
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    b0d278b7
time.c 29.4 KB