On Sat, 25 Jun 2016 01:15:34 +0900 Namhyung Kim <[email protected]> wrote:
> On Fri, Jun 24, 2016 at 12:04:40PM -0400, Steven Rostedt wrote: > > On Fri, 24 Jun 2016 15:35:44 +0900 > > Namhyung Kim <[email protected]> wrote: > > > > > > > > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > > > > > index dea12a6e413b..35c523ba5c59 100644 > > > > > --- a/include/linux/ftrace.h > > > > > +++ b/include/linux/ftrace.h > > > > > @@ -751,25 +751,33 @@ extern void ftrace_init(void); > > > > > static inline void ftrace_init(void) { } > > > > > #endif > > > > > > > > > > +#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS > > > > > +# define FTRACE_ALIGNMENT 4 > > > > > +#else > > > > > +# define FTRACE_ALIGNMENT 8 > > > > > +#endif > > > > > > As far as I can see, the ring buffer has following code in ring_buffer.c: > > #define RB_ALIGNMENT 4U > #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) > #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ > > #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS > # define RB_FORCE_8BYTE_ALIGNMENT 0 > # define RB_ARCH_ALIGNMENT RB_ALIGNMENT > #else > # define RB_FORCE_8BYTE_ALIGNMENT 1 > # define RB_ARCH_ALIGNMENT 8U > #endif > > #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT) > Right, what I meant was that we should just define FTRACE_ALIGNMENT unconditionally to 4. If CONFIG_HAVE_64BIT_ALIGNED_ACCESS is not set, it will add the buffered space regardless. You already moved "overrun", I don't see anything that would be out of alignment if the structure itself is aligned. -- Steve
