From 7816fecd03e480ed0b47d674ed772ca0b45e1b5e Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Sat, 11 Jul 2009 00:29:04 +0000 Subject: [PATCH] sh: Mark __switch_to() as __notrace_funcgraph Annotate __switch_to() so that the function graph tracer does not try to trace it. Use __notrace_funcgraph, as opposed to notrace, so that other tracers can continue to trace __switch_to(). The reason that we don't want to trace __switch_to() with the function graph tracer is because of how the return address stack in task_struct is implemented. When we enter __switch_to we store the real return address on prev's ret_stack. When we return from __switch_to() we've patched the return address on the kernel stack to be return_to_handler. Calling return_to_handler we do, -> ftrace_return_to_handler() -> ftrace_pop_return_ftrace() Which tries to pop the real return address from current->ret_stack. The problem being that we stored the return address on prev->ret_stack, but current now points to next, and next->ret_stack doesn't contain the correct return address (and is possibly even empty). Signed-off-by: Matt Fleming Signed-off-by: Paul Mundt --- arch/sh/kernel/process_32.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/sh/kernel/process_32.c b/arch/sh/kernel/process_32.c index 92d7740..9fee977 100644 --- a/arch/sh/kernel/process_32.c +++ b/arch/sh/kernel/process_32.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -264,8 +265,8 @@ static void ubc_set_tracing(int asid, unsigned long pc) * switch_to(x,y) should switch tasks from x to y. * */ -struct task_struct *__switch_to(struct task_struct *prev, - struct task_struct *next) +__notrace_funcgraph struct task_struct * +__switch_to(struct task_struct *prev, struct task_struct *next) { #if defined(CONFIG_SH_FPU) unlazy_fpu(prev, task_pt_regs(prev)); -- 2.7.4