qemu-kvm/kvm-trace-Clarify-DTrace-SystemTap-help-message.patch

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From 5d45e3a5d2e2d929095489a37579c3b7fc059450 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>
Date: Tue, 3 Sep 2019 14:21:10 +0100
Subject: [PATCH 1/8] trace: Clarify DTrace/SystemTap help message
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: <20190903142110.25673-2-philmd@redhat.com>
Patchwork-id: 90255
O-Subject: [RHEL-AV-8.1.0 qemu-kvm PATCH 1/1] trace: Clarify DTrace/SystemTap help message
Bugzilla: 1516220
RH-Acked-by: John Snow <jsnow@redhat.com>
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Most tracing backends are implemented within QEMU, except the
DTrace/SystemTap backends.
One side effect is when running 'qemu -trace help', an incomplete
list of trace events is displayed when using the DTrace/SystemTap
backends.
This is partly due to trace events registered as modules with
trace_init(), and since the events are not used within QEMU,
the linker optimize and remove the unused modules (which is
OK in this particular case).
Currently only the events compiled in trace-root.o and in the
last trace.o member of libqemuutil.a are linked, resulting in
an incomplete list of events.
To avoid confusion, improve the help message, recommending to
use the proper systemtap script to display the events list.
Before:
$ lm32-softmmu/qemu-system-lm32 -trace help 2>&1 | wc -l
70
After:
$ lm32-softmmu/qemu-system-lm32 -trace help
Run 'qemu-trace-stap list qemu-system-lm32' to print a list
of names of trace points with the DTrace/SystemTap backends.
$ qemu-trace-stap list qemu-system-lm32 | wc -l
1136
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190823142203.5210-1-philmd@redhat.com
Message-Id: <20190823142203.5210-1-philmd@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 9f591a5d95e1969969632ab44cf35e505c8ddc3b)
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
trace/control.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/trace/control.c b/trace/control.c
index 43fb786..d9cafc1 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -165,6 +165,12 @@ void trace_list_events(void)
while ((ev = trace_event_iter_next(&iter)) != NULL) {
fprintf(stderr, "%s\n", trace_event_get_name(ev));
}
+#ifdef CONFIG_TRACE_DTRACE
+ fprintf(stderr, "This list of names of trace points may be incomplete "
+ "when using the DTrace/SystemTap backends.\n"
+ "Run 'qemu-trace-stap list %s' to print the full list.\n",
+ error_get_progname());
+#endif
}
static void do_trace_enable_events(const char *line_buf)
--
1.8.3.1