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authorLinus Torvalds <torvalds@linux-foundation.org>2010-03-13 14:43:01 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-13 14:43:01 -0800
commit4e3eaddd142e2142c048c5052a0a9d2604fccfc6 (patch)
tree5bc45a286502e54e790c54948f22364c5afd9d89 /kernel/trace/ftrace.c
parent8655e7e3ddec60603c4f6c14cdf642e2ba198df8 (diff)
parentb97c4bc16734a2e597dac7f91ee9eb78f4aeef9a (diff)
downloadtalos-obmc-linux-4e3eaddd142e2142c048c5052a0a9d2604fccfc6.tar.gz
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Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: locking: Make sparse work with inline spinlocks and rwlocks x86/mce: Fix RCU lockdep splats rcu: Increase RCU CPU stall timeouts if PROVE_RCU ftrace: Replace read_barrier_depends() with rcu_dereference_raw() rcu: Suppress RCU lockdep warnings during early boot rcu, ftrace: Fix RCU lockdep splat in ftrace_perf_buf_prepare() rcu: Suppress __mpol_dup() false positive from RCU lockdep rcu: Make rcu_read_lock_sched_held() handle !PREEMPT rcu: Add control variables to lockdep_rcu_dereference() diagnostics rcu, cgroup: Relax the check in task_subsys_state() as early boot is now handled by lockdep-RCU rcu: Use wrapper function instead of exporting tasklist_lock sched, rcu: Fix rcu_dereference() for RCU-lockdep rcu: Make task_subsys_state() RCU-lockdep checks handle boot-time use rcu: Fix holdoff for accelerated GPs for last non-dynticked CPU x86/gart: Unexport gart_iommu_aperture Fix trivial conflicts in kernel/trace/ftrace.c
Diffstat (limited to 'kernel/trace/ftrace.c')
-rw-r--r--kernel/trace/ftrace.c22
1 files changed, 13 insertions, 9 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index bb53edbb5c8c..d9062f5cc0c0 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -27,6 +27,7 @@
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/hash.h>
+#include <linux/rcupdate.h>
#include <trace/events/sched.h>
@@ -84,18 +85,22 @@ ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
+/*
+ * Traverse the ftrace_list, invoking all entries. The reason that we
+ * can use rcu_dereference_raw() is that elements removed from this list
+ * are simply leaked, so there is no need to interact with a grace-period
+ * mechanism. The rcu_dereference_raw() calls are needed to handle
+ * concurrent insertions into the ftrace_list.
+ *
+ * Silly Alpha and silly pointer-speculation compiler optimizations!
+ */
static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
{
- struct ftrace_ops *op = ftrace_list;
-
- /* in case someone actually ports this to alpha! */
- read_barrier_depends();
+ struct ftrace_ops *op = rcu_dereference_raw(ftrace_list); /*see above*/
while (op != &ftrace_list_end) {
- /* silly alpha */
- read_barrier_depends();
op->func(ip, parent_ip);
- op = op->next;
+ op = rcu_dereference_raw(op->next); /*see above*/
};
}
@@ -150,8 +155,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
* the ops->next pointer is valid before another CPU sees
* the ops pointer included into the ftrace_list.
*/
- smp_wmb();
- ftrace_list = ops;
+ rcu_assign_pointer(ftrace_list, ops);
if (ftrace_enabled) {
ftrace_func_t func;
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