Merge remote-tracking branch 'stefanha/tracing' into staging

MAINTAINERS

@@ -459,6 +459,12 @@ S: Maintained
 F: slirp/
 T: git://git.kiszka.org/qemu.git queues/slirp
 
+Tracing
+M: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
+S: Maintained
+F: trace/
+T: git://repo.or.cz/qemu/stefanha.git tracing
+
 Usermode Emulation
 ------------------
 BSD user

docs/tracing.txt

@@ -31,8 +31,8 @@ There is a set of static trace events declared in the "trace-events" source
 file.  Each trace event declaration names the event, its arguments, and the
 format string which can be used for pretty-printing:
 
-    qemu_malloc(size_t size, void *ptr) "size %zu ptr %p"
-    qemu_free(void *ptr) "ptr %p"
+    qemu_vmalloc(size_t size, void *ptr) "size %zu ptr %p"
+    qemu_vfree(void *ptr) "ptr %p"
 
 The "trace-events" file is processed by the "tracetool" script during build to
 generate code for the trace events.  Trace events are invoked directly from
@@ -40,14 +40,16 @@ source code like this:
 
     #include "trace.h"  /* needed for trace event prototype */
     
-    void *qemu_malloc(size_t size)
+    void *qemu_vmalloc(size_t size)
     {
         void *ptr;
-        if (!size && !allow_zero_malloc()) {
-            abort();
+        size_t align = QEMU_VMALLOC_ALIGN;
+     
+        if (size < align) {
+            align = getpagesize();
         }
-        ptr = oom_check(malloc(size ? size : 1));
-        trace_qemu_malloc(size, ptr);  /* <-- trace event */
+        ptr = qemu_memalign(align, size);
+        trace_qemu_vmalloc(size, ptr);
         return ptr;
     }
 
@@ -70,11 +72,6 @@ Trace events should use types as follows:
    cannot include all user-defined struct declarations and it is therefore
    necessary to use void * for pointers to structs.
 
-   Pointers (including char *) cannot be dereferenced easily (or at all) in
-   some trace backends.  If pointers are used, ensure they are meaningful by
-   themselves and do not assume the data they point to will be traced.  Do
-   not pass in string arguments.
-
  * For everything else, use primitive scalar types (char, int, long) with the
    appropriate signedness.
 
@@ -182,6 +179,9 @@ source tree.  It may not be as powerful as platform-specific or third-party
 trace backends but it is portable.  This is the recommended trace backend
 unless you have specific needs for more advanced backends.
 
+The "simple" backend currently does not capture string arguments, it simply
+records the char* pointer value instead of the string that is pointed to.
+
 ==== Monitor commands ====
 
 * info trace

trace/simple.c

@@ -12,8 +12,10 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <time.h>
+#ifndef _WIN32
 #include <signal.h>
 #include <pthread.h>
+#endif
 #include "qemu-timer.h"
 #include "trace.h"
 #include "trace/control.h"
@@ -54,9 +56,9 @@ enum {
  * Trace records are written out by a dedicated thread.  The thread waits for
  * records to become available, writes them out, and then waits again.
  */
-static pthread_mutex_t trace_lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t trace_available_cond = PTHREAD_COND_INITIALIZER;
-static pthread_cond_t trace_empty_cond = PTHREAD_COND_INITIALIZER;
+static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
+static GCond *trace_available_cond;
+static GCond *trace_empty_cond;
 static bool trace_available;
 static bool trace_writeout_enabled;
 
@@ -93,29 +95,30 @@ static bool get_trace_record(unsigned int idx, TraceRecord *record)
  */
 static void flush_trace_file(bool wait)
 {
-    pthread_mutex_lock(&trace_lock);
+    g_static_mutex_lock(&trace_lock);
     trace_available = true;
-    pthread_cond_signal(&trace_available_cond);
+    g_cond_signal(trace_available_cond);
 
     if (wait) {
-        pthread_cond_wait(&trace_empty_cond, &trace_lock);
+        g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
     }
 
-    pthread_mutex_unlock(&trace_lock);
+    g_static_mutex_unlock(&trace_lock);
 }
 
 static void wait_for_trace_records_available(void)
 {
-    pthread_mutex_lock(&trace_lock);
+    g_static_mutex_lock(&trace_lock);
     while (!(trace_available && trace_writeout_enabled)) {
-        pthread_cond_signal(&trace_empty_cond);
-        pthread_cond_wait(&trace_available_cond, &trace_lock);
+        g_cond_signal(trace_empty_cond);
+        g_cond_wait(trace_available_cond,
+                    g_static_mutex_get_mutex(&trace_lock));
     }
     trace_available = false;
-    pthread_mutex_unlock(&trace_lock);
+    g_static_mutex_unlock(&trace_lock);
 }
 
-static void *writeout_thread(void *opaque)
+static gpointer writeout_thread(gpointer opaque)
 {
     TraceRecord record;
     unsigned int writeout_idx = 0;
@@ -159,7 +162,7 @@ static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
 
     timestamp = get_clock();
 
-    idx = __sync_fetch_and_add(&trace_idx, 1) % TRACE_BUF_LEN;
+    idx = g_atomic_int_exchange_and_add((gint *)&trace_idx, 1) % TRACE_BUF_LEN;
     trace_buf[idx] = (TraceRecord){
         .event = event,
         .timestamp_ns = timestamp,
@@ -231,7 +234,7 @@ void st_set_trace_file_enabled(bool enable)
             .x1 = HEADER_VERSION,
         };
 
-        trace_fp = fopen(trace_file_name, "w");
+        trace_fp = fopen(trace_file_name, "wb");
         if (!trace_fp) {
             return;
         }
@@ -331,28 +334,47 @@ bool trace_event_set_state(const char *name, bool state)
     return false;
 }
 
-bool trace_backend_init(const char *events, const char *file)
+/* Helper function to create a thread with signals blocked.  Use glib's
+ * portable threads since QEMU abstractions cannot be used due to reentrancy in
+ * the tracer.  Also note the signal masking on POSIX hosts so that the thread
+ * does not steal signals when the rest of the program wants them blocked.
+ */
+static GThread *trace_thread_create(GThreadFunc fn)
 {
-    pthread_t thread;
-    pthread_attr_t attr;
+    GThread *thread;
+#ifndef _WIN32
     sigset_t set, oldset;
-    int ret;
-
-    pthread_attr_init(&attr);
-    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 
     sigfillset(&set);
     pthread_sigmask(SIG_SETMASK, &set, &oldset);
-    ret = pthread_create(&thread, &attr, writeout_thread, NULL);
+#endif
+    thread = g_thread_create(writeout_thread, NULL, FALSE, NULL);
+#ifndef _WIN32
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+#endif
 
-    if (ret != 0) {
-        fprintf(stderr, "warning: unable to initialize simple trace backend\n");
-    } else {
-        atexit(st_flush_trace_buffer);
-        trace_backend_init_events(events);
-        st_set_trace_file(file);
+    return thread;
+}
+
+bool trace_backend_init(const char *events, const char *file)
+{
+    GThread *thread;
+
+    if (!g_thread_supported()) {
+        g_thread_init(NULL);
     }
 
+    trace_available_cond = g_cond_new();
+    trace_empty_cond = g_cond_new();
+
+    thread = trace_thread_create(writeout_thread);
+    if (!thread) {
+        fprintf(stderr, "warning: unable to initialize simple trace backend\n");
+        return false;
+    }
+
+    atexit(st_flush_trace_buffer);
+    trace_backend_init_events(events);
+    st_set_trace_file(file);
     return true;
 }