tools: Add guest trace agent as a user tool
This patch adds a user tool, "trace agent" for sending trace data of a guest to
a Host in low overhead. This agent has the following functions:
- splice a page of ring-buffer to read_pipe without memory copying
- splice the page from write_pipe to virtio-console without memory copying
- write trace data to stdout by using -o option
- controlled by start/stop orders from a Host
Changes in v2:
- Cleanup (change fprintf() to pr_err() and an include guard)
Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Acked-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/tools/virtio/virtio-trace/trace-agent-ctl.c b/tools/virtio/virtio-trace/trace-agent-ctl.c
new file mode 100644
index 0000000..a2d0403
--- /dev/null
+++ b/tools/virtio/virtio-trace/trace-agent-ctl.c
@@ -0,0 +1,137 @@
+/*
+ * Controller of read/write threads for virtio-trace
+ *
+ * Copyright (C) 2012 Hitachi, Ltd.
+ * Created by Yoshihiro Yunomae <yoshihiro.yunomae.ez@hitachi.com>
+ * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
+ *
+ * Licensed under GPL version 2 only.
+ *
+ */
+
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <poll.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "trace-agent.h"
+
+#define HOST_MSG_SIZE 256
+#define EVENT_WAIT_MSEC 100
+
+static volatile sig_atomic_t global_signal_val;
+bool global_sig_receive; /* default false */
+bool global_run_operation; /* default false*/
+
+/* Handle SIGTERM/SIGINT/SIGQUIT to exit */
+static void signal_handler(int sig)
+{
+ global_signal_val = sig;
+}
+
+int rw_ctl_init(const char *ctl_path)
+{
+ int ctl_fd;
+
+ ctl_fd = open(ctl_path, O_RDONLY);
+ if (ctl_fd == -1) {
+ pr_err("Cannot open ctl_fd\n");
+ goto error;
+ }
+
+ return ctl_fd;
+
+error:
+ exit(EXIT_FAILURE);
+}
+
+static int wait_order(int ctl_fd)
+{
+ struct pollfd poll_fd;
+ int ret = 0;
+
+ while (!global_sig_receive) {
+ poll_fd.fd = ctl_fd;
+ poll_fd.events = POLLIN;
+
+ ret = poll(&poll_fd, 1, EVENT_WAIT_MSEC);
+
+ if (global_signal_val) {
+ global_sig_receive = true;
+ pr_info("Receive interrupt %d\n", global_signal_val);
+
+ /* Wakes rw-threads when they are sleeping */
+ if (!global_run_operation)
+ pthread_cond_broadcast(&cond_wakeup);
+
+ ret = -1;
+ break;
+ }
+
+ if (ret < 0) {
+ pr_err("Polling error\n");
+ goto error;
+ }
+
+ if (ret)
+ break;
+ };
+
+ return ret;
+
+error:
+ exit(EXIT_FAILURE);
+}
+
+/*
+ * contol read/write threads by handling global_run_operation
+ */
+void *rw_ctl_loop(int ctl_fd)
+{
+ ssize_t rlen;
+ char buf[HOST_MSG_SIZE];
+ int ret;
+
+ /* Setup signal handlers */
+ signal(SIGTERM, signal_handler);
+ signal(SIGINT, signal_handler);
+ signal(SIGQUIT, signal_handler);
+
+ while (!global_sig_receive) {
+
+ ret = wait_order(ctl_fd);
+ if (ret < 0)
+ break;
+
+ rlen = read(ctl_fd, buf, sizeof(buf));
+ if (rlen < 0) {
+ pr_err("read data error in ctl thread\n");
+ goto error;
+ }
+
+ if (rlen == 2 && buf[0] == '1') {
+ /*
+ * If host writes '1' to a control path,
+ * this controller wakes all read/write threads.
+ */
+ global_run_operation = true;
+ pthread_cond_broadcast(&cond_wakeup);
+ pr_debug("Wake up all read/write threads\n");
+ } else if (rlen == 2 && buf[0] == '0') {
+ /*
+ * If host writes '0' to a control path, read/write
+ * threads will wait for notification from Host.
+ */
+ global_run_operation = false;
+ pr_debug("Stop all read/write threads\n");
+ } else
+ pr_info("Invalid host notification: %s\n", buf);
+ }
+
+ return NULL;
+
+error:
+ exit(EXIT_FAILURE);
+}