Version 2.5.7

[lttng-ust.git] / libringbuffer / frontend_internal.h

diff --git a/libringbuffer/frontend_internal.h b/libringbuffer/frontend_internal.h
index 77a431295a71b495d72fff3de74c31b8aff761eb..51b652d2a3d2ed5dbb9eb41d0942a522bd4c86a7 100644 (file)
--- a/libringbuffer/frontend_internal.h
+++ b/libringbuffer/frontend_internal.h
@@ -365,6 +365,13 @@ void lib_ring_buffer_wakeup(struct lttng_ust_lib_ring_buffer *buf,
        }
 }
 
+/*
+ * Receive end of subbuffer TSC as parameter. It has been read in the
+ * space reservation loop of either reserve or switch, which ensures it
+ * progresses monotonically with event records in the buffer. Therefore,
+ * it ensures that the end timestamp of a subbuffer is <= begin
+ * timestamp of the following subbuffers.
+ */
 static inline
 void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config,
                                   struct lttng_ust_lib_ring_buffer *buf,
@@ -372,11 +379,11 @@ void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config
                                   unsigned long offset,
                                   unsigned long commit_count,
                                   unsigned long idx,
-                                  struct lttng_ust_shm_handle *handle)
+                                  struct lttng_ust_shm_handle *handle,
+                                  uint64_t tsc)
 {
        unsigned long old_commit_count = commit_count
                                         - chan->backend.subbuf_size;
-       uint64_t tsc;
 
        /* Check if all commits have been done */
        if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)
@@ -407,6 +414,12 @@ void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config
                 * The subbuffer size is least 2 bytes (minimum size: 1 page).
                 * This guarantees that old_commit_count + 1 != commit_count.
                 */
+
+               /*
+                * Order prior updates to reserve count prior to the
+                * commit_cold cc_sb update.
+                */
+               cmm_smp_wmb();
                if (caa_likely(v_cmpxchg(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb,
                                         old_commit_count, old_commit_count + 1)
                           == old_commit_count)) {
@@ -416,7 +429,6 @@ void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config
                         * and any other writer trying to access this subbuffer
                         * in this state is required to drop records.
                         */
-                       tsc = config->cb.ring_buffer_clock_read(chan);
                        v_add(config,
                              subbuffer_get_records_count(config,
                                                          &buf->backend,
@@ -452,6 +464,11 @@ void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config
                        /* End of exclusive subbuffer access */
                        v_set(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb,
                              commit_count);
+                       /*
+                        * Order later updates to reserve count after
+                        * the commit cold cc_sb update.
+                        */
+                       cmm_smp_wmb();
                        lib_ring_buffer_vmcore_check_deliver(config, buf,
                                                 commit_count, idx, handle);
 
@@ -482,23 +499,20 @@ void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer
                                          unsigned long idx,
                                          unsigned long buf_offset,
                                          unsigned long commit_count,
-                                         size_t slot_size,
                                          struct lttng_ust_shm_handle *handle)
 {
-       unsigned long offset, commit_seq_old;
+       unsigned long commit_seq_old;
 
        if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)
                return;
 
-       offset = buf_offset + slot_size;
-
        /*
         * subbuf_offset includes commit_count_mask. We can simply
         * compare the offsets within the subbuffer without caring about
         * buffer full/empty mismatch because offset is never zero here
         * (subbuffer header and record headers have non-zero length).
         */
-       if (caa_unlikely(subbuf_offset(offset - commit_count, chan)))
+       if (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan)))
                return;
 
        commit_seq_old = v_read(config, &shmp_index(handle, buf->commit_hot, idx)->seq);