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author | Rainer Weikusat <rweikusat@mobileactivedefense.com> | 2011-02-28 04:50:55 +0000 |
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committer | David S. Miller <davem@davemloft.net> | 2011-03-07 15:31:16 -0800 |
commit | b3ca9b02b00704053a38bfe4c31dbbb9c13595d0 (patch) | |
tree | aee22e55bb36b3f8cffc22f840a958a8a6ea184b /net/unix/af_unix.c | |
parent | 2ea6d8c446752008df7f37867f0cf7483533b05e (diff) | |
download | lwn-b3ca9b02b00704053a38bfe4c31dbbb9c13595d0.tar.gz lwn-b3ca9b02b00704053a38bfe4c31dbbb9c13595d0.zip |
net: fix multithreaded signal handling in unix recv routines
The unix_dgram_recvmsg and unix_stream_recvmsg routines in
net/af_unix.c utilize mutex_lock(&u->readlock) calls in order to
serialize read operations of multiple threads on a single socket. This
implies that, if all n threads of a process block in an AF_UNIX recv
call trying to read data from the same socket, one of these threads
will be sleeping in state TASK_INTERRUPTIBLE and all others in state
TASK_UNINTERRUPTIBLE. Provided that a particular signal is supposed to
be handled by a signal handler defined by the process and that none of
this threads is blocking the signal, the complete_signal routine in
kernel/signal.c will select the 'first' such thread it happens to
encounter when deciding which thread to notify that a signal is
supposed to be handled and if this is one of the TASK_UNINTERRUPTIBLE
threads, the signal won't be handled until the one thread not blocking
on the u->readlock mutex is woken up because some data to process has
arrived (if this ever happens). The included patch fixes this by
changing mutex_lock to mutex_lock_interruptible and handling possible
error returns in the same way interruptions are handled by the actual
receive-code.
Signed-off-by: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/unix/af_unix.c')
-rw-r--r-- | net/unix/af_unix.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index dd419d286204..437a99e560e1 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1724,7 +1724,11 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock, msg->msg_namelen = 0; - mutex_lock(&u->readlock); + err = mutex_lock_interruptible(&u->readlock); + if (err) { + err = sock_intr_errno(sock_rcvtimeo(sk, noblock)); + goto out; + } skb = skb_recv_datagram(sk, flags, noblock, &err); if (!skb) { @@ -1864,7 +1868,11 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, memset(&tmp_scm, 0, sizeof(tmp_scm)); } - mutex_lock(&u->readlock); + err = mutex_lock_interruptible(&u->readlock); + if (err) { + err = sock_intr_errno(timeo); + goto out; + } do { int chunk; @@ -1895,11 +1903,12 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, timeo = unix_stream_data_wait(sk, timeo); - if (signal_pending(current)) { + if (signal_pending(current) + || mutex_lock_interruptible(&u->readlock)) { err = sock_intr_errno(timeo); goto out; } - mutex_lock(&u->readlock); + continue; unlock: unix_state_unlock(sk); |