ide: Handle irq disabling consistently

ide_timer_expiry() disables interrupt at function entry when acquiring
hwif->lock. Before disabling the device interrupt it unlocks hwif->lock,
but interrupts stay disabled. After the call to disable_irq() interrupts
are disabled again, which is a pointless exercise.

After the device irq handler has been invoked with interrupts disabled,
hwif->lock is acquired again with spin_lock_irq() because the device irq
handler might have reenabled interrupts. This is not documented and
confusing for the casual reader.

Remove the redundant local_irq_disable() and add a comment which explains
why hwif->lock has to be reacquired with spin_lock_irq().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c
index 6f25da5..a444bad 100644 (file)
--- a/drivers/ide/ide-io.c
+++ b/drivers/ide/ide-io.c
@@ -659,8 +659,7 @@ void ide_timer_expiry (struct timer_list *t)
                spin_unlock(&hwif->lock);
                /* disable_irq_nosync ?? */
                disable_irq(hwif->irq);
-               /* local CPU only, as if we were handling an interrupt */
-               local_irq_disable();
+
                if (hwif->polling) {
                        startstop = handler(drive);
                } else if (drive_is_ready(drive)) {
@@ -679,6 +678,7 @@ void ide_timer_expiry (struct timer_list *t)
                                startstop = ide_error(drive, "irq timeout",
                                        hwif->tp_ops->read_status(hwif));
                }
+               /* Disable interrupts again, `handler' might have enabled it */
                spin_lock_irq(&hwif->lock);
                enable_irq(hwif->irq);
                if (startstop == ide_stopped && hwif->polling == 0) {