Commit 26c01624 authored Jun 02, 2009 by Steven Rostedt Committed by Steven Rostedt Jun 02, 2009

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@goodmis.org>

parent 82310a32

kernel/trace/ftrace.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -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);