Commit-ID: 26c01624a2a40f8a4ddf6449b65c9b1c418d0e72
Gitweb: http://git.kernel.org/tip/26c01624a2a40f8a4ddf6449b65c9b1c418d0e72
Author: Steven Rostedt <srostedt@xxxxxxxxxx>
AuthorDate: Tue, 2 Jun 2009 14:01:19 -0400
Committer: Steven Rostedt <rostedt@xxxxxxxxxxx>
CommitDate: Tue, 2 Jun 2009 14:42:17 -0400
function-graph: add memory barriers for accessing task's ret_stack
The code that handles the tasks ret_stack allocation for every task
assumes that only an interrupt can cause issues (even though interrupts
are disabled).
In reality, the code is allocating the ret_stack for tasks that may be
running on other CPUs and there are not efficient memory barriers to
handle this case.
[ Impact: prevent crash due to using of uninitialized ret_stack variables ]
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
kernel/trace/ftrace.c | 8 ++++----
1 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 20e0660..1664d3f 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2580,12 +2580,12 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
}
if (t->ret_stack == NULL) {
- t->curr_ret_stack = -1;
- /* Make sure IRQs see the -1 first: */
- barrier();
- t->ret_stack = ret_stack_list[start++];
atomic_set(&t->tracing_graph_pause, 0);
atomic_set(&t->trace_overrun, 0);
+ t->curr_ret_stack = -1;
+ /* Make sure the tasks see the -1 first: */
+ smp_wmb();
+ t->ret_stack = ret_stack_list[start++];
}
} while_each_thread(g, t);
--
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