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authorBjorn Andersson <bjorn.andersson@linaro.org>2020-01-14 10:57:02 +0300
committerDavid S. Miller <davem@davemloft.net>2020-01-15 05:36:42 +0300
commitf16a4b26f31f95dddb12cf3c2390906a735203ae (patch)
tree88a2188c8fb7fc91d2a41ac4ab6ed5e98acbf304 /net/qrtr
parent0a7e0d0ef05440db03c3199e84d228db943b237f (diff)
downloadlinux-f16a4b26f31f95dddb12cf3c2390906a735203ae.tar.xz
net: qrtr: Make qrtr_port_lookup() use RCU
The important part of qrtr_port_lookup() wrt synchronization is that the function returns a reference counted struct qrtr_sock, or fail. As such we need only to ensure that an decrement of the object's refcount happens inbetween the finding of the object in the idr and qrtr_port_lookup()'s own increment of the object. By using RCU and putting a synchronization point after we remove the mapping from the idr, but before it can be released we achieve this - with the benefit of not having to hold the mutex in qrtr_port_lookup(). Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/qrtr')
-rw-r--r--net/qrtr/qrtr.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c
index ca802798e19e..0fe08f060b8c 100644
--- a/net/qrtr/qrtr.c
+++ b/net/qrtr/qrtr.c
@@ -646,11 +646,11 @@ static struct qrtr_sock *qrtr_port_lookup(int port)
if (port == QRTR_PORT_CTRL)
port = 0;
- mutex_lock(&qrtr_port_lock);
+ rcu_read_lock();
ipc = idr_find(&qrtr_ports, port);
if (ipc)
sock_hold(&ipc->sk);
- mutex_unlock(&qrtr_port_lock);
+ rcu_read_unlock();
return ipc;
}
@@ -692,6 +692,10 @@ static void qrtr_port_remove(struct qrtr_sock *ipc)
mutex_lock(&qrtr_port_lock);
idr_remove(&qrtr_ports, port);
mutex_unlock(&qrtr_port_lock);
+
+ /* Ensure that if qrtr_port_lookup() did enter the RCU read section we
+ * wait for it to up increment the refcount */
+ synchronize_rcu();
}
/* Assign port number to socket.