[lxc-devel] [PATCH] RFC: commands: handle epipe
Stéphane Graber
stgraber at ubuntu.com
Tue Mar 25 22:02:09 UTC 2014
On Tue, Mar 25, 2014 at 05:58:32PM -0400, Dwight Engen wrote:
> On Tue, 25 Mar 2014 15:50:06 -0500
> Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
>
> > If we start a lxc_wait on a container while it is exiting, it is
> > possible that we open the command socket, then the monitor closes
> > all its mainloop sockets and exit, then we send our credentials.
> > Then we get killed by SIGPIPE.
>
> Hey Serge, this is an interesting condition. I'm a bit confused where
> the race is, looking at lxc_wait it looks like we get the monitor open
> before opening the command socket with lxc_getstate, and the monitor
> shouldn't exit while we are still a client of it.
It's a race which has been causing dozens of testrun failures on the CI
infrastructure, so it's reasonably easy to hit :)
And I think Serge meant s/monitor/command/ in there, the SIGPIPE we were
getting was from the command socket when the container was about to die
and exit.
>
> > Handle that case, recognizing that if we get sigpipe then the
> > container is (now) stopped.
>
> This makes sense in general, so I agree with the change.
>
> > Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
> > ---
> > src/lxc/af_unix.c | 4 ++--
> > src/lxc/commands.c | 11 ++++++++++-
> > 2 files changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/src/lxc/af_unix.c b/src/lxc/af_unix.c
> > index a2de73e..46d8e50 100644
> > --- a/src/lxc/af_unix.c
> > +++ b/src/lxc/af_unix.c
> > @@ -158,7 +158,7 @@ int lxc_abstract_unix_send_fd(int fd, int sendfd,
> > void *data, size_t size) msg.msg_iov = &iov;
> > msg.msg_iovlen = 1;
> >
> > - return sendmsg(fd, &msg, 0);
> > + return sendmsg(fd, &msg, MSG_NOSIGNAL);
> > }
> >
> > int lxc_abstract_unix_recv_fd(int fd, int *recvfd, void *data,
> > size_t size) @@ -230,7 +230,7 @@ int
> > lxc_abstract_unix_send_credential(int fd, void *data, size_t size)
> > msg.msg_iov = &iov; msg.msg_iovlen = 1;
> >
> > - return sendmsg(fd, &msg, 0);
> > + return sendmsg(fd, &msg, MSG_NOSIGNAL);
> > }
> >
> > int lxc_abstract_unix_rcv_credential(int fd, void *data, size_t size)
> > diff --git a/src/lxc/commands.c b/src/lxc/commands.c
> > index 6b46c2c..b71274c 100644
> > --- a/src/lxc/commands.c
> > +++ b/src/lxc/commands.c
> > @@ -263,6 +263,8 @@ static int lxc_cmd(const char *name, struct
> > lxc_cmd_rr *cmd, int *stopped,
> > ret = lxc_abstract_unix_send_credential(sock, &cmd->req,
> > sizeof(cmd->req)); if (ret != sizeof(cmd->req)) {
> > + if (errno == EPIPE)
> > + goto epipe;
> > SYSERROR("command %s failed to send req to '@%s' %d",
> > lxc_cmd_str(cmd->req.cmd), offset, ret);
> > if (ret >=0)
> > @@ -271,8 +273,10 @@ static int lxc_cmd(const char *name, struct
> > lxc_cmd_rr *cmd, int *stopped, }
> >
> > if (cmd->req.datalen > 0) {
> > - ret = send(sock, cmd->req.data, cmd->req.datalen, 0);
> > + ret = send(sock, cmd->req.data, cmd->req.datalen,
> > MSG_NOSIGNAL); if (ret != cmd->req.datalen) {
> > + if (errno == EPIPE)
> > + goto epipe;
> > SYSERROR("command %s failed to send request
> > data to '@%s' %d", lxc_cmd_str(cmd->req.cmd), offset, ret);
> > if (ret >=0)
> > @@ -289,6 +293,11 @@ out:
> > cmd->rsp.ret = sock;
> >
> > return ret;
> > +
> > +epipe:
> > + close(sock);
> > + *stopped = 1;
> > + return 0;
> > }
> >
> > int lxc_try_cmd(const char *name, const char *lxcpath)
>
> _______________________________________________
> lxc-devel mailing list
> lxc-devel at lists.linuxcontainers.org
> http://lists.linuxcontainers.org/listinfo/lxc-devel
--
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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