Performance: remove rcu read lock from ring buffer get/put cpu

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

diff --git a/libringbuffer/frontend_api.h b/libringbuffer/frontend_api.h
index 24f94acf110b5f663443207d3711e3bbe323fa39..77a269184fcf1f3dbc26380f7e2e201cd25bd497 100644 (file)
--- a/libringbuffer/frontend_api.h
+++ b/libringbuffer/frontend_api.h
@@ -1,34 +1,46 @@
-#ifndef _LINUX_RING_BUFFER_FRONTEND_API_H
-#define _LINUX_RING_BUFFER_FRONTEND_API_H
+#ifndef _LTTNG_RING_BUFFER_FRONTEND_API_H
+#define _LTTNG_RING_BUFFER_FRONTEND_API_H
 
 /*
- * linux/ringbuffer/frontend_api.h
+ * libringbuffer/frontend_api.h
  *
- * (C) Copyright 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  *
  * Ring Buffer Library Synchronization Header (buffer write API).
  *
  * Author:
- *     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * See ring_buffer_frontend.c for more information on wait-free algorithms.
- * See linux/ringbuffer/frontend.h for channel allocation and read-side API.
+ *      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
- * Dual LGPL v2.1/GPL v2 license.
+ * See ring_buffer_frontend.c for more information on wait-free
+ * algorithms.
+ * See frontend.h for channel allocation and read-side API.
  */
 
 #include "frontend.h"
-#include "lttng/core.h"
 #include <urcu-bp.h>
 #include <urcu/compiler.h>
 
 /**
  * lib_ring_buffer_get_cpu - Precedes ring buffer reserve/commit.
  *
- * Grabs RCU read-side lock and keeps a ring buffer nesting count as
- * supplementary safety net to ensure tracer client code will never
- * trigger an endless recursion. Returns the processor ID on success,
- * -EPERM on failure (nesting count too high).
+ * Keeps a ring buffer nesting count as supplementary safety net to
+ * ensure tracer client code will never trigger an endless recursion.
+ * Returns the processor ID on success, -EPERM on failure (nesting count
+ * too high).
  *
  * asm volatile and "memory" clobber prevent the compiler from moving
  * instructions out of the ring buffer nesting count. This is required to ensure
@@ -41,14 +53,13 @@ int lib_ring_buffer_get_cpu(const struct lttng_ust_lib_ring_buffer_config *confi
 {
        int cpu, nesting;
 
-       rcu_read_lock();
-       cpu = ust_get_cpu();
-       nesting = ++lib_ring_buffer_nesting;    /* TLS */
+       cpu = lttng_ust_get_cpu();
+       nesting = ++URCU_TLS(lib_ring_buffer_nesting);
        cmm_barrier();
 
        if (caa_unlikely(nesting > 4)) {
                WARN_ON_ONCE(1);
-               lib_ring_buffer_nesting--;      /* TLS */
+               URCU_TLS(lib_ring_buffer_nesting)--;
                rcu_read_unlock();
                return -EPERM;
        } else
@@ -62,8 +73,7 @@ static inline
 void lib_ring_buffer_put_cpu(const struct lttng_ust_lib_ring_buffer_config *config)
 {
        cmm_barrier();
-       lib_ring_buffer_nesting--;              /* TLS */
-       rcu_read_unlock();
+       URCU_TLS(lib_ring_buffer_nesting)--;            /* TLS */
 }
 
 /*
@@ -276,14 +286,13 @@ void lib_ring_buffer_commit(const struct lttng_ust_lib_ring_buffer_config *confi
        commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, endidx)->cc);
 
        lib_ring_buffer_check_deliver(config, buf, chan, offset_end - 1,
-                                     commit_count, endidx, handle);
+                                     commit_count, endidx, handle, ctx->tsc);
        /*
         * Update used size at each commit. It's needed only for extracting
         * ring_buffer buffers from vmcore, after crash.
         */
        lib_ring_buffer_write_commit_counter(config, buf, chan, endidx,
-                                            ctx->buf_offset, commit_count,
-                                            ctx->slot_size, handle);
+                       offset_end, commit_count, handle);
 }
 
 /**
@@ -352,4 +361,4 @@ void lib_ring_buffer_record_enable(const struct lttng_ust_lib_ring_buffer_config
        uatomic_dec(&buf->record_disabled);
 }
 
-#endif /* _LINUX_RING_BUFFER_FRONTEND_API_H */
+#endif /* _LTTNG_RING_BUFFER_FRONTEND_API_H */