On Mon, 9 Jan 2017, Josh Poimboeuf wrote: > In the following commit: > > 0100301bfdf5 ("sched/x86: Rewrite the switch_to() code") > > ... the layout of the 'inactive_task_frame' struct was designed to have > a frame pointer header embedded in it, so that the unwinder could use > the 'bp' and 'ret_addr' fields to report __schedule() on the stack (or > ret_from_fork() for newly forked tasks which haven't actually run yet). > > Finish the job by changing get_frame_pointer() to return a pointer to > inactive_task_frame's 'bp' field rather than 'bp' itself. This allows > the unwinder to start one frame higher on the stack, so that it properly > reports __schedule(). > > Reported-by: Miroslav Benes <mbe...@suse.cz>
You can also add my Tested-by: Miroslav Benes <mbe...@suse.cz> One ignorant question below. > Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> > --- > arch/x86/include/asm/stacktrace.h | 5 +---- > arch/x86/include/asm/switch_to.h | 10 +++++++++- > 2 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/include/asm/stacktrace.h > b/arch/x86/include/asm/stacktrace.h > index 20ce3db..2e41c50 100644 > --- a/arch/x86/include/asm/stacktrace.h > +++ b/arch/x86/include/asm/stacktrace.h > @@ -52,16 +52,13 @@ static inline bool on_stack(struct stack_info *info, void > *addr, size_t len) > static inline unsigned long * > get_frame_pointer(struct task_struct *task, struct pt_regs *regs) > { > - struct inactive_task_frame *frame; > - > if (regs) > return (unsigned long *)regs->bp; > > if (task == current) > return __builtin_frame_address(0); > > - frame = (struct inactive_task_frame *)task->thread.sp; > - return (unsigned long *)READ_ONCE_NOCHECK(frame->bp); > + return &((struct inactive_task_frame *)task->thread.sp)->bp; You effectively remove one of the changes from the previous patch - READ_ONCE_NOCHECK. Is it intentional? Regards, Miroslav