Messages in this thread Patch in this message | | | Subject | [RFC PATCH 09/11] trace-cmd: Use poll(2) to wait for a message | From | Yoshihiro YUNOMAE <> | Date | Mon, 19 Aug 2013 18:46:42 +0900 |
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Use poll(2) to wait for a message. If a client/server cannot send a message for any reasons, the current server/client will wait in a blocking read operation. So, we use poll(2) for avoiding remaining in a blocking state.
This modification avoids to try to connect to an old-version client. An old-version network server will send a message "tracecmd" first, and an old-version client will start to send cpu number, pagesize, and option. By introducing trace-msg, the new client sends a message "MSG_TCONNECT" first, so the start point of the connection is different. If the old client tries to connect to the new network server, the server should make the connection close. A server applied this patch will die when the predetermined time will have elapsed.
Note that if a new client tries to connect to an old server, the new client will automatically die. This is because the new client which received the inappropriate message "tracecmd" will die.
Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com> --- trace-msg.c | 50 ++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 42 insertions(+), 8 deletions(-)
diff --git a/trace-msg.c b/trace-msg.c index 777ea1f..36117cd 100644 --- a/trace-msg.c +++ b/trace-msg.c @@ -435,6 +435,27 @@ error: return -ENOMSG; } +#define MSG_WAIT_MSEC 5000 + +/* + * A return value of 0 indicates time-out + */ +static int tracecmd_msg_recv_wait(int fd, char *buf, struct tracecmd_msg **msg) +{ + struct pollfd pfd; + int ret; + + pfd.fd = fd; + pfd.events = POLLIN; + ret = poll(&pfd, 1, MSG_WAIT_MSEC); + if (ret < 0) { + return -errno; + } else if (ret == 0) + return -ETIMEDOUT; + + return tracecmd_msg_recv(fd, buf); +} + static void *tracecmd_msg_buf_access(struct tracecmd_msg *msg, int offset) { return (void *)msg + offset; @@ -448,9 +469,12 @@ static int tracecmd_msg_wait_for_msg(int fd, struct tracecmd_msg **msg) u32 cmd; int ret; - ret = tracecmd_msg_recv(fd, msg_tmp); - if (ret < 0) + ret = tracecmd_msg_recv_wait(fd, msg_tmp, msg); + if (ret < 0) { + if (ret == -ETIMEDOUT) + warning("Connection timed out\n"); return ret; + } *msg = (struct tracecmd_msg *)msg_tmp; cmd = ntohl((*msg)->cmd); @@ -549,9 +573,13 @@ int tracecmd_msg_set_connection(int fd) int ret; /* wait for connection msg by a client first */ - ret = tracecmd_msg_recv(fd, buf); + ret = tracecmd_msg_recv_wait(fd, buf, &msg); if (ret < 0) { - warning("Disconnect"); + if (ret == -ETIMEDOUT) + /* network connection will be started soon */ + warning("No connection message"); + else + warning("Disconnect"); return ret; } @@ -586,9 +614,12 @@ int tracecmd_msg_initial_setting(int fd, int *cpus, int *pagesize) u32 size = 0; u32 cmd; - ret = tracecmd_msg_recv(fd, buf); - if (ret < 0) + ret = tracecmd_msg_recv_wait(fd, buf, &msg); + if (ret < 0) { + if (ret == -ETIMEDOUT) + warning("Connection timed out\n"); return ret; + } msg = (struct tracecmd_msg *)buf; cmd = ntohl(msg->cmd); @@ -724,9 +755,12 @@ int tracecmd_msg_collect_metadata(int ifd, int ofd) int ret; do { - ret = tracecmd_msg_recv(ifd, buf); + ret = tracecmd_msg_recv_wait(ifd, buf, &msg); if (ret < 0) { - warning("reading client"); + if (ret == -ETIMEDOUT) + warning("Connection timed out\n"); + else + warning("reading client"); return ret; }
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