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trace/simple: Fix unauthorized enable 

st_set_trace_file() accidentally enables tracing.  It's called
unconditionally during startup, which is why QEMU built with the
simple trace backend always writes a trace file "trace-$PID".

This has been broken for quite a while.  I didn't track down the exact
commit.

Fix st_set_trace_file() to restore the state.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200527065613.25322-1-armbru@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Markus Armbruster 2020-05-27 08:56:13 +02:00 committed by Stefan Hajnoczi
parent f892b494fa
commit db25d56c01
2 changed files with 15 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
trace/simple.c
View File

@ -302,10 +302,17 @@ static int st_write_event_mapping(void)
return 0; return 0;
} }
void st_set_trace_file_enabled(bool enable) /**
* Enable / disable tracing, return whether it was enabled.
*
* @enable: enable if %true, else disable.
*/
bool st_set_trace_file_enabled(bool enable)
{ {
bool was_enabled = trace_fp;
if (enable == !!trace_fp) { if (enable == !!trace_fp) {
return; /* no change */ return was_enabled; /* no change */
} }
/* Halt trace writeout */ /* Halt trace writeout */
@ -323,14 +330,14 @@ void st_set_trace_file_enabled(bool enable)
trace_fp = fopen(trace_file_name, "wb"); trace_fp = fopen(trace_file_name, "wb");
if (!trace_fp) { if (!trace_fp) {
return; return was_enabled;
} }
if (fwrite(&header, sizeof header, 1, trace_fp) != 1 || if (fwrite(&header, sizeof header, 1, trace_fp) != 1 ||
st_write_event_mapping() < 0) { st_write_event_mapping() < 0) {
fclose(trace_fp); fclose(trace_fp);
trace_fp = NULL; trace_fp = NULL;
return; return was_enabled;
} }
/* Resume trace writeout */ /* Resume trace writeout */
@ -340,6 +347,7 @@ void st_set_trace_file_enabled(bool enable)
fclose(trace_fp); fclose(trace_fp);
trace_fp = NULL; trace_fp = NULL;
} }
return was_enabled;
} }
/** /**
@ -350,7 +358,7 @@ void st_set_trace_file_enabled(bool enable)
*/ */
void st_set_trace_file(const char *file) void st_set_trace_file(const char *file)
{ {
st_set_trace_file_enabled(false); bool saved_enable = st_set_trace_file_enabled(false);
g_free(trace_file_name); g_free(trace_file_name);
@ -361,7 +369,7 @@ void st_set_trace_file(const char *file)
trace_file_name = g_strdup_printf("%s", file); trace_file_name = g_strdup_printf("%s", file);
} }
st_set_trace_file_enabled(true); st_set_trace_file_enabled(saved_enable);
} }
void st_print_trace_file_status(void) void st_print_trace_file_status(void)

2
trace/simple.h
View File

@ -12,7 +12,7 @@
#define TRACE_SIMPLE_H #define TRACE_SIMPLE_H
void st_print_trace_file_status(void); void st_print_trace_file_status(void);
void st_set_trace_file_enabled(bool enable); bool st_set_trace_file_enabled(bool enable);
void st_set_trace_file(const char *file); void st_set_trace_file(const char *file);
bool st_init(void); bool st_init(void);
void st_flush_trace_buffer(void); void st_flush_trace_buffer(void);