Patchwork [2/4] trace: Direct access of atomics is verboten, use the API

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Submitter Stefan Hajnoczi
Date Feb. 6, 2013, 3:30 p.m.
Message ID <1360164617-12103-3-git-send-email-stefanha@redhat.com>
Download mbox | patch
Permalink /patch/218676/
State New
Headers show

Comments

Stefan Hajnoczi - Feb. 6, 2013, 3:30 p.m.
From: Markus Armbruster <armbru@redhat.com>

The GLib Reference Manual says:

    It is very important that all accesses to a particular integer or
    pointer be performed using only this API and that different sizes
    of operation are not mixed or used on overlapping memory
    regions. Never read or assign directly from or to a value --
    always use this API.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 trace/simple.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Patch

diff --git a/trace/simple.c b/trace/simple.c
index ccbdb6a..592ff48 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -166,13 +166,13 @@  static gpointer writeout_thread(gpointer opaque)
     for (;;) {
         wait_for_trace_records_available();
 
-        if (dropped_events) {
+        if (g_atomic_int_get(&dropped_events)) {
             dropped.rec.event = DROPPED_EVENT_ID,
             dropped.rec.timestamp_ns = get_clock();
             dropped.rec.length = sizeof(TraceRecord) + sizeof(uint64_t),
             dropped.rec.reserved = 0;
             while (1) {
-                dropped_count = dropped_events;
+                dropped_count = g_atomic_int_get(&dropped_events);
                 if (g_atomic_int_compare_and_exchange(&dropped_events,
                                                       dropped_count, 0)) {
                     break;
@@ -214,7 +214,7 @@  int trace_record_start(TraceBufferRecord *rec, TraceEventID event, size_t datasi
     uint64_t timestamp_ns = get_clock();
 
     while (1) {
-        old_idx = trace_idx;
+        old_idx = g_atomic_int_get(&trace_idx);
         smp_rmb();
         new_idx = old_idx + rec_len;
 
@@ -275,7 +275,8 @@  void trace_record_finish(TraceBufferRecord *rec)
     record.event |= TRACE_RECORD_VALID;
     write_to_buffer(rec->tbuf_idx, &record, sizeof(TraceRecord));
 
-    if ((trace_idx - writeout_idx) > TRACE_BUF_FLUSH_THRESHOLD) {
+    if ((g_atomic_int_get(&trace_idx) - writeout_idx)
+        > TRACE_BUF_FLUSH_THRESHOLD) {
         flush_trace_file(false);
     }
 }