Messages in this thread Patch in this message | | | Date | Tue, 02 Jun 2009 14:30:39 -0400 | From | Steven Rostedt <> | Subject | [PATCH 3/3] function-graph: add memory barriers for accessing tasks ret_stack |
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From: Steven Rostedt <srostedt@redhat.com>
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@goodmis.org> --- 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); -- 1.6.3.1 --
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