From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 1 Mar 2012 18:53:45 +0000 (-0500)
Subject: Fix ABI: add padding to structures shared between UST and consumer
X-Git-Tag: v2.0.0-rc2~7
X-Git-Url: http://git.lttng.org/?p=lttng-ust.git;a=commitdiff_plain;h=3c8964ba54f920c4a33b1e371c4c07ddcdc40383

Fix ABI: add padding to structures shared between UST and consumer

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/libringbuffer/backend_types.h b/libringbuffer/backend_types.h
index 3d8bd3cb..81e67119 100644
--- a/libringbuffer/backend_types.h
+++ b/libringbuffer/backend_types.h
@@ -15,12 +15,14 @@
 #include "shm_internal.h"
 #include "vatomic.h"
 
+#define RB_BACKEND_PAGES_PADDING	16
 struct lttng_ust_lib_ring_buffer_backend_pages {
 	unsigned long mmap_offset;	/* offset of the subbuffer in mmap */
 	union v_atomic records_commit;	/* current records committed count */
 	union v_atomic records_unread;	/* records to read */
 	unsigned long data_size;	/* Amount of data to read from subbuf */
 	DECLARE_SHMP(char, p);		/* Backing memory map */
+	char padding[RB_BACKEND_PAGES_PADDING];
 };
 
 struct lttng_ust_lib_ring_buffer_backend_subbuffer {
@@ -38,6 +40,7 @@ struct lttng_ust_lib_ring_buffer_backend_pages_shmp {
 	DECLARE_SHMP(struct lttng_ust_lib_ring_buffer_backend_pages, shmp);
 };
 
+#define RB_BACKEND_RING_BUFFER_PADDING		64
 struct lttng_ust_lib_ring_buffer_backend {
 	/* Array of ring_buffer_backend_subbuffer for writer */
 	DECLARE_SHMP(struct lttng_ust_lib_ring_buffer_backend_subbuffer, buf_wsb);
@@ -54,12 +57,14 @@ struct lttng_ust_lib_ring_buffer_backend {
 	int cpu;			/* This buffer's cpu. -1 if global. */
 	union v_atomic records_read;	/* Number of records read */
 	unsigned int allocated:1;	/* is buffer allocated ? */
+	char padding[RB_BACKEND_RING_BUFFER_PADDING];
 };
 
 struct lttng_ust_lib_ring_buffer_shmp {
 	DECLARE_SHMP(struct lttng_ust_lib_ring_buffer, shmp); /* Channel per-cpu buffers */
 };
 
+#define RB_BACKEND_CHANNEL_PADDING	64
 struct channel_backend {
 	unsigned long buf_size;		/* Size of the buffer */
 	unsigned long subbuf_size;	/* Sub-buffer size */
@@ -75,6 +80,7 @@ struct channel_backend {
 	DECLARE_SHMP(void *, priv_data);/* Client-specific information */
 	struct lttng_ust_lib_ring_buffer_config config; /* Ring buffer configuration */
 	char name[NAME_MAX];		/* Channel name */
+	char padding[RB_BACKEND_CHANNEL_PADDING];
 	struct lttng_ust_lib_ring_buffer_shmp buf[];
 };
 
diff --git a/libringbuffer/frontend_types.h b/libringbuffer/frontend_types.h
index 961c90e5..1d47b275 100644
--- a/libringbuffer/frontend_types.h
+++ b/libringbuffer/frontend_types.h
@@ -34,6 +34,7 @@
 enum switch_mode { SWITCH_ACTIVE, SWITCH_FLUSH };
 
 /* channel: collection of per-cpu ring buffers. */
+#define RB_CHANNEL_PADDING	64
 struct channel {
 	int record_disabled;
 	unsigned long commit_count_mask;	/*
@@ -53,20 +54,26 @@ struct channel {
 	 * be last member.
 	 */
 	struct channel_backend backend;		/* Associated backend */
+	char padding[RB_CHANNEL_PADDING];
 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 
 /* Per-subbuffer commit counters used on the hot path */
+#define RB_COMMIT_COUNT_HOT_PADDING	16
 struct commit_counters_hot {
 	union v_atomic cc;		/* Commit counter */
 	union v_atomic seq;		/* Consecutive commits */
+	char padding[RB_COMMIT_COUNT_HOT_PADDING];
 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 
 /* Per-subbuffer commit counters used only on cold paths */
+#define RB_COMMIT_COUNT_COLD_PADDING	24
 struct commit_counters_cold {
 	union v_atomic cc_sb;		/* Incremented _once_ at sb switch */
+	char padding[RB_COMMIT_COUNT_COLD_PADDING];
 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 
 /* ring buffer state */
+#define RB_RING_BUFFER_PADDING		64
 struct lttng_ust_lib_ring_buffer {
 	/* First 32 bytes cache-hot cacheline */
 	union v_atomic offset;		/* Current offset in the buffer */
@@ -109,6 +116,7 @@ struct lttng_ust_lib_ring_buffer {
 		read_timer_enabled:1;	/* Protected by ring_buffer_nohz_lock */
 	/* shmp pointer to self */
 	DECLARE_SHMP(struct lttng_ust_lib_ring_buffer, self);
+	char padding[RB_RING_BUFFER_PADDING];
 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 
 static inline