ring buffer: handle shmp errors

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

diff --git a/libringbuffer/frontend_internal.h b/libringbuffer/frontend_internal.h
index 10d6c4db789bbf498e3188a1a339c5e94223653f..68aa70223ea5529acd3ecdf67a3c9b4057fcdb49 100644 (file)
--- a/libringbuffer/frontend_internal.h
+++ b/libringbuffer/frontend_internal.h
@@ -233,10 +233,14 @@ int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_con
                                      struct lttng_ust_shm_handle *handle)
 {
        unsigned long offset, idx, commit_count;
+       struct commit_counters_hot *cc_hot = shmp_index(handle, buf->commit_hot, idx);
 
        CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU);
        CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU);
 
+       if (caa_unlikely(!cc_hot))
+               return 0;
+
        /*
         * Read offset and commit count in a loop so they are both read
         * atomically wrt interrupts. By deal with interrupt concurrency by
@@ -248,7 +252,7 @@ int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_con
        do {
                offset = v_read(config, &buf->offset);
                idx = subbuf_index(offset, chan);
-               commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, idx)->cc);
+               commit_count = v_read(config, &cc_hot->cc);
        } while (offset != v_read(config, &buf->offset));
 
        return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)