| Message ID | 20141022221245.GE17252@oracle.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Sowmini Varadhan <sowmini.varadhan@oracle.com> Date: Wed, 22 Oct 2014 18:12:45 -0400 > > For NAPIfied drivers , there is no need to > synchronize by doing irqsave/restore on vio.lock in the I/O > path. > > Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com> Conditional locking is broken locking, and the bug you introduce here is a good example of why that is. If the vio->timer has to be triggered when vio_port_up() is invoked, it will next run fron in_softirq() context regardless of whether the user is sunvnet or sunvdc. So it will elide the locking regardless of who is using this vio context. Never, ever, use conditional locking. This locking is harmless overhead in a slow path, just leave it alone for now. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/sparc/kernel/viohs.c b/arch/sparc/kernel/viohs.c index 526fcb5..92e2a32 100644 --- a/arch/sparc/kernel/viohs.c +++ b/arch/sparc/kernel/viohs.c @@ -747,10 +747,11 @@ EXPORT_SYMBOL(vio_ldc_free); void vio_port_up(struct vio_driver_state *vio) { - unsigned long flags; + unsigned long flags = 0; int err, state; - spin_lock_irqsave(&vio->lock, flags); + if (!in_softirq()) + spin_lock_irqsave(&vio->lock, flags); state = ldc_state(vio->lp); @@ -777,7 +778,8 @@ void vio_port_up(struct vio_driver_state *vio) mod_timer(&vio->timer, expires); } - spin_unlock_irqrestore(&vio->lock, flags); + if (!in_softirq()) + spin_unlock_irqrestore(&vio->lock, flags); } EXPORT_SYMBOL(vio_port_up);
For NAPIfied drivers , there is no need to synchronize by doing irqsave/restore on vio.lock in the I/O path. Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com> --- arch/sparc/kernel/viohs.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)