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

Submitted by Markus Armbruster on Jan. 25, 2013, 3:43 p.m.

Details

Message ID 1359128620-14226-3-git-send-email-armbru@redhat.com
State New
Headers show

Commit Message

Markus Armbruster Jan. 25, 2013, 3:43 p.m.
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>
---
 trace/simple.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Comments

Laszlo Ersek Jan. 31, 2013, 11:25 a.m.
On 01/25/13 16:43, Markus Armbruster wrote:
> 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>
> ---
>  trace/simple.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)

Nothing beats a patch summary with a word that English loans from the
submitter's mother tongue! :) Extra points for the Vau.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Harsh Prateek Bora Jan. 31, 2013, 11:59 a.m.
On 01/25/2013 09:13 PM, Markus Armbruster wrote:
> 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: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>

> ---
>   trace/simple.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
>
> 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);
>       }
>   }
>

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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);
     }
 }