From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 24 Dec 2014 17:24:04 +0000 (-0500)
Subject: Fix: lttng_this_cpu_ptr wrapper for kernel 3.19+
X-Git-Tag: v2.6.0~9
X-Git-Url: https://git.lttng.org/?p=lttng-modules.git;a=commitdiff_plain;h=1816623505f9a0111fa5041da63f8e1099b6ffcc

Fix: lttng_this_cpu_ptr wrapper for kernel 3.19+

Starting from kernel 3.19-rc1, __get_cpu_var() disappears, replaced by
this_cpu_ptr(). Introduce a wrapper using either depending on the kernel
version. Older kernels did not expose a this_cpu_ptr(), so keep on using
__get_cpu_var() on old kernels.

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

diff --git a/lib/ringbuffer/frontend_api.h b/lib/ringbuffer/frontend_api.h
index ff6abce9..b622bd7e 100644
--- a/lib/ringbuffer/frontend_api.h
+++ b/lib/ringbuffer/frontend_api.h
@@ -30,6 +30,7 @@
  */
 
 #include "../../wrapper/ringbuffer/frontend.h"
+#include "../../wrapper/percpu-defs.h"
 #include <linux/errno.h>
 #include <linux/prefetch.h>
 
@@ -73,7 +74,7 @@ static inline
 void lib_ring_buffer_put_cpu(const struct lib_ring_buffer_config *config)
 {
 	barrier();
-	__get_cpu_var(lib_ring_buffer_nesting)--;
+	(*lttng_this_cpu_ptr(&lib_ring_buffer_nesting))--;
 	rcu_read_unlock_sched_notrace();
 }
 
diff --git a/lib/ringbuffer/ring_buffer_frontend.c b/lib/ringbuffer/ring_buffer_frontend.c
index ae0b9e39..c4b797ce 100644
--- a/lib/ringbuffer/ring_buffer_frontend.c
+++ b/lib/ringbuffer/ring_buffer_frontend.c
@@ -61,6 +61,7 @@
 #include "../../wrapper/ringbuffer/iterator.h"
 #include "../../wrapper/ringbuffer/nohz.h"
 #include "../../wrapper/atomic.h"
+#include "../../wrapper/percpu-defs.h"
 
 /*
  * Internal structure representing offsets to use at a sub-buffer switch.
@@ -498,16 +499,16 @@ static int notrace ring_buffer_tick_nohz_callback(struct notifier_block *nb,
 		raw_spin_unlock(&buf->raw_tick_nohz_spinlock);
 		break;
 	case TICK_NOHZ_STOP:
-		spin_lock(&__get_cpu_var(ring_buffer_nohz_lock));
+		spin_lock(lttng_this_cpu_ptr(&ring_buffer_nohz_lock));
 		lib_ring_buffer_stop_switch_timer(buf);
 		lib_ring_buffer_stop_read_timer(buf);
-		spin_unlock(&__get_cpu_var(ring_buffer_nohz_lock));
+		spin_unlock(lttng_this_cpu_ptr(&ring_buffer_nohz_lock));
 		break;
 	case TICK_NOHZ_RESTART:
-		spin_lock(&__get_cpu_var(ring_buffer_nohz_lock));
+		spin_lock(lttng_this_cpu_ptr(&ring_buffer_nohz_lock));
 		lib_ring_buffer_start_read_timer(buf);
 		lib_ring_buffer_start_switch_timer(buf);
-		spin_unlock(&__get_cpu_var(ring_buffer_nohz_lock));
+		spin_unlock(lttng_this_cpu_ptr(&ring_buffer_nohz_lock));
 		break;
 	}
 
diff --git a/wrapper/percpu-defs.h b/wrapper/percpu-defs.h
new file mode 100644
index 00000000..bba1bcea
--- /dev/null
+++ b/wrapper/percpu-defs.h
@@ -0,0 +1,42 @@
+#ifndef _LTTNG_WRAPPER_PERCPU_DEFS_H
+#define _LTTNG_WRAPPER_PERCPU_DEFS_H
+
+/*
+ * wrapper/percpu-defs.h
+ *
+ * wrapper around linux/percpu-defs.h.
+ *
+ * Copyright (C) 2014 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
+ */
+
+#include <linux/version.h>
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,19,0)
+
+#include <linux/percpu-defs.h>
+
+#define lttng_this_cpu_ptr(ptr)		this_cpu_ptr(ptr)
+
+#else /* #if LINUX_VERSION_CODE >= KERNEL_VERSION(3,19,0) */
+
+#include <linux/percpu.h>
+
+#define lttng_this_cpu_ptr(ptr)		(&__get_cpu_var(*(ptr)))
+
+#endif /* #else #if LINUX_VERSION_CODE >= KERNEL_VERSION(3,19,0) */
+
+#endif /* _LTTNG_WRAPPER_PERCPU_DEFS_H */
diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h
index 5705d0c2..1b2821a1 100644
--- a/wrapper/trace-clock.h
+++ b/wrapper/trace-clock.h
@@ -36,6 +36,7 @@
 #include <linux/version.h>
 #include <asm/local.h>
 #include "../lttng-kernel-version.h"
+#include "percpu-defs.h"
 #include "random.h"
 
 #if LTTNG_KERNEL_RANGE(3,10,0, 3,10,14) || LTTNG_KERNEL_RANGE(3,11,0, 3,11,3)
@@ -97,7 +98,7 @@ static inline u64 trace_clock_monotonic_wrapper(void)
 	local_t *last_tsc;
 
 	/* Use fast nmi-safe monotonic clock provided by the Linux kernel. */
-	last_tsc = &__get_cpu_var(lttng_last_tsc);
+	last_tsc = lttng_this_cpu_ptr(&lttng_last_tsc);
 	last = local_read(last_tsc);
 	/*
 	 * Read "last" before "now". It is not strictly required, but it ensures