X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=lib%2Fringbuffer%2Fring_buffer_frontend.c;h=2626afa31e3ea9f33a7e9ebbab98bd91d510b723;hb=74b9312477538922f7ce3194b37ed3e0c5d7ba16;hp=dc0357f56a3e71547c7da80a4e2bd3ce7277d0f0;hpb=79b18ef7332e6f75826f9b0e568b47394e98b127;p=lttng-modules.git

diff --git a/lib/ringbuffer/ring_buffer_frontend.c b/lib/ringbuffer/ring_buffer_frontend.c
index dc0357f5..2626afa3 100644
--- a/lib/ringbuffer/ring_buffer_frontend.c
+++ b/lib/ringbuffer/ring_buffer_frontend.c
@@ -1424,6 +1424,19 @@ int lib_ring_buffer_try_switch_slow(enum switch_mode mode,
 	 */
 	if (mode == SWITCH_FLUSH || off > 0) {
 		if (unlikely(off == 0)) {
+                        /*
+			 * A final flush that encounters an empty
+			 * sub-buffer cannot switch buffer if a
+			 * reader is located within this sub-buffer.
+			 * Anyway, the purpose of final flushing of a
+			 * sub-buffer at offset 0 is to handle the case
+			 * of entirely empty stream.
+			 */
+			if (unlikely(subbuf_trunc(offsets->begin, chan)
+					- subbuf_trunc((unsigned long)
+						atomic_long_read(&buf->consumed), chan)
+					>= chan->backend.buf_size))
+				return -1;
 			/*
 			 * The client does not save any header information.
 			 * Don't switch empty subbuffer on finalize, because it