| Message ID | 1544566543-3395-3-git-send-email-pkaustub@cisco.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Jason Gunthorpe |
| Headers | show |
| Series | IB/usnic: usnic bug fixes | expand |
On Tue, Dec 11, 2018 at 02:15:42PM -0800, Parvi Kaustubhi wrote: > Acquiring the rtnl lock while holding usdev_lock could result in a > deadlock. > > For example: > > usnic_ib_query_port() > | mutex_lock(&us_ibdev->usdev_lock) > | ib_get_eth_speed() > | rtnl_lock() > > rtnl_lock() > | usnic_ib_netdevice_event() > | mutex_lock(&us_ibdev->usdev_lock) > > This commit moves the usdev_lock acquisition after the rtnl lock has > been released. > This is safe to do because usdev_lock is not protecting anything being > accessed in ib_get_eth_speed(). Hence, the correct order of holding > locks > (rtnl -> usdev_lock) is not violated. > > Signed-off-by: Parvi Kaustubhi <pkaustub@cisco.com> > --- > drivers/infiniband/hw/usnic/usnic_ib_verbs.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) Applied to for-next, thanks Jason
diff --git a/drivers/infiniband/hw/usnic/usnic_ib_verbs.c b/drivers/infiniband/hw/usnic/usnic_ib_verbs.c index 0b91ff3..598e23c 100644 --- a/drivers/infiniband/hw/usnic/usnic_ib_verbs.c +++ b/drivers/infiniband/hw/usnic/usnic_ib_verbs.c @@ -336,13 +336,16 @@ int usnic_ib_query_port(struct ib_device *ibdev, u8 port, usnic_dbg("\n"); - mutex_lock(&us_ibdev->usdev_lock); if (ib_get_eth_speed(ibdev, port, &props->active_speed, - &props->active_width)) { - mutex_unlock(&us_ibdev->usdev_lock); + &props->active_width)) return -EINVAL; - } + /* + * usdev_lock is acquired after (and not before) ib_get_eth_speed call + * because acquiring rtnl_lock in ib_get_eth_speed, while holding + * usdev_lock could lead to a deadlock. + */ + mutex_lock(&us_ibdev->usdev_lock); /* props being zeroed by the caller, avoid zeroing it here */ props->lid = 0;
Acquiring the rtnl lock while holding usdev_lock could result in a deadlock. For example: usnic_ib_query_port() | mutex_lock(&us_ibdev->usdev_lock) | ib_get_eth_speed() | rtnl_lock() rtnl_lock() | usnic_ib_netdevice_event() | mutex_lock(&us_ibdev->usdev_lock) This commit moves the usdev_lock acquisition after the rtnl lock has been released. This is safe to do because usdev_lock is not protecting anything being accessed in ib_get_eth_speed(). Hence, the correct order of holding locks (rtnl -> usdev_lock) is not violated. Signed-off-by: Parvi Kaustubhi <pkaustub@cisco.com> --- drivers/infiniband/hw/usnic/usnic_ib_verbs.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)