Calculate context length outside of retry loop

[lttng-modules.git] / lib / ringbuffer / ring_buffer_frontend.c

diff --git a/lib/ringbuffer/ring_buffer_frontend.c b/lib/ringbuffer/ring_buffer_frontend.c
index e454ac97c168ac6ea6671c01b80ffda03c13c17c..310752506550bda15e03d6d57eff5d5f7a43398c 100644 (file)
--- a/lib/ringbuffer/ring_buffer_frontend.c
+++ b/lib/ringbuffer/ring_buffer_frontend.c
@@ -1075,15 +1075,6 @@ int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
        unsigned long consumed_cur, write_offset;
        int finalized;
 
-       /*
-        * First, ensure we perform a "final" flush onto the stream.  This will
-        * ensure we create a packet of padding if we encounter an empty
-        * packet. This ensures the time-stamps right before the snapshot is
-        * used as end of packet timestamp.
-        */
-       if (!buf->quiescent)
-               _lib_ring_buffer_switch_remote(buf, SWITCH_FLUSH);
-
 retry:
        finalized = ACCESS_ONCE(buf->finalized);
        /*
@@ -1504,8 +1495,7 @@ void lib_ring_buffer_print_errors(struct channel *chan,
 /*
  * lib_ring_buffer_switch_old_start: Populate old subbuffer header.
  *
- * Only executed by SWITCH_FLUSH, which can be issued while tracing is active
- * or at buffer finalization (destroy).
+ * Only executed when the buffer is finalized, in SWITCH_FLUSH.
  */
 static
 void lib_ring_buffer_switch_old_start(struct lib_ring_buffer *buf,
@@ -1701,14 +1691,12 @@ int lib_ring_buffer_try_switch_slow(enum switch_mode mode,
                unsigned long sb_index, commit_count;
 
                /*
-                * We are performing a SWITCH_FLUSH. There may be concurrent
-                * writes into the buffer if e.g. invoked while performing a
-                * snapshot on an active trace.
+                * We are performing a SWITCH_FLUSH. At this stage, there are no
+                * concurrent writes into the buffer.
                 *
-                * If the client does not save any header information (sub-buffer
-                * header size == 0), don't switch empty subbuffer on finalize,
-                * because it is invalid to deliver a completely empty
-                * subbuffer.
+                * The client does not save any header information.  Don't
+                * switch empty subbuffer on finalize, because it is invalid to
+                * deliver a completely empty subbuffer.
                 */
                if (!config->cb.subbuffer_header_size())
                        return -1;
@@ -1873,12 +1861,20 @@ static void _lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf,
        put_online_cpus();
 }
 
+/* Switch sub-buffer if current sub-buffer is non-empty. */
 void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf)
 {
        _lib_ring_buffer_switch_remote(buf, SWITCH_ACTIVE);
 }
 EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_remote);
 
+/* Switch sub-buffer even if current sub-buffer is empty. */
+void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf)
+{
+       _lib_ring_buffer_switch_remote(buf, SWITCH_FLUSH);
+}
+EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_remote_empty);
+
 /*
  * Returns :
  * 0 if ok
@@ -1890,7 +1886,8 @@ static
 int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
                                     struct channel *chan,
                                     struct switch_offsets *offsets,
-                                    struct lib_ring_buffer_ctx *ctx)
+                                    struct lib_ring_buffer_ctx *ctx,
+                                    void *client_ctx)
 {
        const struct lib_ring_buffer_config *config = &chan->backend.config;
        unsigned long reserve_commit_diff, offset_cmp;
@@ -1916,7 +1913,7 @@ retry:
                offsets->size = config->cb.record_header_size(config, chan,
                                                offsets->begin,
                                                &offsets->pre_header_padding,
-                                               ctx);
+                                               ctx, client_ctx);
                offsets->size +=
                        lib_ring_buffer_align(offsets->begin + offsets->size,
                                              ctx->largest_align)
@@ -2000,7 +1997,7 @@ retry:
                        config->cb.record_header_size(config, chan,
                                                offsets->begin,
                                                &offsets->pre_header_padding,
-                                               ctx);
+                                               ctx, client_ctx);
                offsets->size +=
                        lib_ring_buffer_align(offsets->begin + offsets->size,
                                              ctx->largest_align)
@@ -2064,7 +2061,8 @@ EXPORT_SYMBOL_GPL(lib_ring_buffer_lost_event_too_big);
  * -EIO for other errors, else returns 0.
  * It will take care of sub-buffer switching.
  */
-int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx)
+int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx,
+               void *client_ctx)
 {
        struct channel *chan = ctx->chan;
        const struct lib_ring_buffer_config *config = &chan->backend.config;
@@ -2077,7 +2075,7 @@ int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx)
 
        do {
                ret = lib_ring_buffer_try_reserve_slow(buf, chan, &offsets,
-                                                      ctx);
+                                                      ctx, client_ctx);
                if (unlikely(ret))
                        return ret;
        } while (unlikely(v_cmpxchg(config, &buf->offset, offsets.old,