On 02/05/2016 02:59 PM, Rainer Weikusat wrote: > Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx> writes: >> Hi Rainer, >> >> A kernel bug report was opened against Ubuntu [0]. After a kernel >> bisect, it was found that reverting the following commit resolved this bug: >> >> commit 3822b5c2fc62e3de8a0f33806ff279fb7df92432 >> Author: Rainer Weikusat <rweikusat@xxxxxxxxxxxxxxxxxxxxxxx> >> Date: Wed Dec 16 20:09:25 2015 +0000 >> >> af_unix: Revert 'lock_interruptible' in stream receive code >> >> >> The regression was introduced as of v4.4-rc6. >> >> I was hoping to get your feedback, since you are the patch author. Do >> you think gathering any additional data will help diagnose this issue, >> or would it be best to submit a revert request? > Funny little problem :-). The code using the interruptible lock cleared > err as side effect hence the > > out: > return copied ? : err; > > at the end of unix_stream_read_generic didn't return the -ENOTSUP put > into err at the start of the function if copied was zero after the loop > because the size of the passed data buffer was zero. > > The following patch should fix this: > > --------- > diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c > index 49d5093..c3e1a08 100644 > --- a/net/unix/af_unix.c > +++ b/net/unix/af_unix.c > @@ -2300,6 +2300,7 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state) > else > skip = 0; > > + err = 0; > do { > int chunk; > bool drop_skb; > ---------- > > I was just about to go the the supermarket to buy an apple when I > received the mail. I didn't even compile the change above yet, however, > I'll do so once I'm back and then submit something formal. > > Here's a test program which can be compiled with a C compiler: > ------------ > #define _GNU_SOURCE > > #include <stdlib.h> > #include <stdio.h> > #include <sys/socket.h> > #include <sys/stat.h> > #include <assert.h> > #include <errno.h> > #include <string.h> > > int main(void) > { > enum { server, client, size }; > int socket_fd[size]; > int const opt = 1; > > assert(socketpair(AF_LOCAL, SOCK_STREAM, 0, socket_fd) == 0); > > char const msg[] = "A random message"; > send(socket_fd[client], msg, sizeof msg, MSG_DONTWAIT | MSG_NOSIGNAL); > > assert(setsockopt(socket_fd[server], SOL_SOCKET, SO_PASSCRED, &opt, sizeof(opt)) != -1); > > union { > struct cmsghdr cmh; > char control[CMSG_SPACE(sizeof(struct ucred))]; > } control_un; > > control_un.cmh.cmsg_len = CMSG_LEN(sizeof(struct ucred)); > control_un.cmh.cmsg_level = SOL_SOCKET; > control_un.cmh.cmsg_type = SCM_CREDENTIALS; > > struct msghdr msgh; > msgh.msg_name = NULL; > msgh.msg_namelen = 0; > msgh.msg_iov = NULL; > msgh.msg_iovlen = 0; > msgh.msg_control = control_un.control; > msgh.msg_controllen = sizeof(control_un.control); > > errno = 0; > > if (recvmsg(socket_fd[server], &msgh, MSG_PEEK) == -1) > { > printf("Error: %s\n", strerror(errno)); > exit(EXIT_FAILURE); > } > else > { > printf("Success!\n"); > exit(EXIT_SUCCESS); > } > } Thanks for the feedback. Just curious, was it a green apple or a red apple? :-) -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html