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authorFrederic Weisbecker <fweisbec@gmail.com>2008-12-02 00:20:39 +0100
committerIngo Molnar <mingo@elte.hu>2008-12-02 09:47:48 +0100
commit48d68b20d00865035b8b65e69af343d0f53fac9d (patch)
treeeca27c0cf9486ae83c7e3193709abae099d1f019 /kernel
parent222658e08f72cd539d01f3aabdc258c596f487e2 (diff)
tracing/function-graph-tracer: support for x86-64
Impact: extend and enable the function graph tracer to 64-bit x86 This patch implements the support for function graph tracer under x86-64. Both static and dynamic tracing are supported. This causes some small CPP conditional asm on arch/x86/kernel/ftrace.c I wanted to use probe_kernel_read/write to make the return address saving/patching code more generic but it causes tracing recursion. That would be perhaps useful to implement a notrace version of these function for other archs ports. Note that arch/x86/process_64.c is not traced, as in X86-32. I first thought __switch_to() was responsible of crashes during tracing because I believed current task were changed inside but that's actually not the case (actually yes, but not the "current" pointer). So I will have to investigate to find the functions that harm here, to enable tracing of the other functions inside (but there is no issue at this time, while process_64.c stays out of -pg flags). A little possible race condition is fixed inside this patch too. When the tracer allocate a return stack dynamically, the current depth is not initialized before but after. An interrupt could occur at this time and, after seeing that the return stack is allocated, the tracer could try to trace it with a random uninitialized depth. It's a prevention, even if I hadn't problems with it. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/ftrace.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 08b536a2614..f7249962752 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1673,8 +1673,10 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
}
if (t->ret_stack == NULL) {
- t->ret_stack = ret_stack_list[start++];
t->curr_ret_stack = -1;
+ /* Make sure IRQs see the -1 first: */
+ barrier();
+ t->ret_stack = ret_stack_list[start++];
atomic_set(&t->trace_overrun, 0);
}
} while_each_thread(g, t);