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packet: don't unconditionally schedule() in case of MSG_DONTWAIT 

In tpacket_snd(), when we've discovered a first frame that is
not in status TP_STATUS_SEND_REQUEST, and return a NULL buffer,
we exit the send routine in case of MSG_DONTWAIT, since we've
finished traversing the mmaped send ring buffer and don't care
about pending frames.

While doing so, we still unconditionally call an expensive
schedule() in the packet_current_frame() "error" path, which
is unnecessary in this case since it's enough to just quit
the function.

Also, in case MSG_DONTWAIT is not set, we should rather test
for need_resched() first and do schedule() only if necessary
since meanwhile pending frames could already have finished
processing and called skb destructor.

Change-Id: Ic83ad580914e70fbffb871ded8ee9045f4679da4
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2014-01-15 16:25:35 +01:00 committed by syphyr
parent bd9cd435ab
commit 41304bf063
1 changed files with 6 additions and 7 deletions
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13
net/packet/af_packet.c
View File

@ -2103,6 +2103,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
int err, reserve = 0;
void *ph;
struct sockaddr_ll *saddr = (struct sockaddr_ll *)msg->msg_name;
bool need_wait = !(msg->msg_flags & MSG_DONTWAIT);
unsigned char *addr = NULL;
int tp_len, size_max;
int len_sum = 0;
@ -2150,10 +2151,10 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
do {
ph = packet_current_frame(po, &po->tx_ring,
TP_STATUS_SEND_REQUEST);
TP_STATUS_SEND_REQUEST);
if (unlikely(ph == NULL)) {
schedule();
if (need_wait && need_resched())
schedule();
continue;
}
@ -2206,10 +2207,8 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
}
packet_increment_head(&po->tx_ring);
len_sum += tp_len;
} while (likely((ph != NULL) ||
((!(msg->msg_flags & MSG_DONTWAIT)) &&
(atomic_read(&po->tx_ring.pending))))
);
} while (likely((ph != NULL) || (need_wait &&
atomic_read(&po->tx_ring.pending))));
err = len_sum;
goto out_put;