X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=lib%2Fringbuffer%2Fring_buffer_frontend.c;h=e77d789bb866b99f1ca1e28c652cc2cc50f450d1;hb=90715ba61e3fa66c1bb438138c8716c6e72356f9;hp=dc1ee450a4eb8dad6bf8f9ecff4332c65ae460d6;hpb=500c99a45fc0da09d1dc7b9e62bf58d562856a9a;p=lttng-modules.git

diff --git a/lib/ringbuffer/ring_buffer_frontend.c b/lib/ringbuffer/ring_buffer_frontend.c
index dc1ee450..e77d789b 100644
--- a/lib/ringbuffer/ring_buffer_frontend.c
+++ b/lib/ringbuffer/ring_buffer_frontend.c
@@ -54,6 +54,7 @@
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
+#include <asm/cacheflush.h>
 
 #include <wrapper/ringbuffer/config.h>
 #include <wrapper/ringbuffer/backend.h>
@@ -1149,6 +1150,47 @@ void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
 }
 EXPORT_SYMBOL_GPL(lib_ring_buffer_move_consumer);
 
+#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
+static void lib_ring_buffer_flush_read_subbuf_dcache(
+		const struct lib_ring_buffer_config *config,
+		struct channel *chan,
+		struct lib_ring_buffer *buf)
+{
+	struct lib_ring_buffer_backend_pages *pages;
+	unsigned long sb_bindex, id, i, nr_pages;
+
+	if (config->output != RING_BUFFER_MMAP)
+		return;
+
+	/*
+	 * Architectures with caches aliased on virtual addresses may
+	 * use different cache lines for the linear mapping vs
+	 * user-space memory mapping. Given that the ring buffer is
+	 * based on the kernel linear mapping, aligning it with the
+	 * user-space mapping is not straightforward, and would require
+	 * extra TLB entries. Therefore, simply flush the dcache for the
+	 * entire sub-buffer before reading it.
+	 */
+	id = buf->backend.buf_rsb.id;
+	sb_bindex = subbuffer_id_get_index(config, id);
+	pages = buf->backend.array[sb_bindex];
+	nr_pages = buf->backend.num_pages_per_subbuf;
+	for (i = 0; i < nr_pages; i++) {
+		struct lib_ring_buffer_backend_page *backend_page;
+
+		backend_page = &pages->p[i];
+		flush_dcache_page(pfn_to_page(backend_page->pfn));
+	}
+}
+#else
+static void lib_ring_buffer_flush_read_subbuf_dcache(
+		const struct lib_ring_buffer_config *config,
+		struct channel *chan,
+		struct lib_ring_buffer *buf)
+{
+}
+#endif
+
 /**
  * lib_ring_buffer_get_subbuf - get exclusive access to subbuffer for reading
  * @buf: ring buffer
@@ -1291,6 +1333,8 @@ retry:
 	buf->get_subbuf_consumed = consumed;
 	buf->get_subbuf = 1;
 
+	lib_ring_buffer_flush_read_subbuf_dcache(config, chan, buf);
+
 	return 0;
 
 nodata: