On Fri, 11 Jul 2014 22:50:45 +0200
Ard Biesheuvel <[email protected]> wrote:
> Commit f7f7bac9cb1c ("rcu: Have the RCU tracepoints use the tracepoint_string
> infrastructure") unconditionally populates the __tracepoint_str input section,
> but this section is not assigned an output section if CONFIG_TRACING is not
> set.
> This results in the __tracepoint_str turning up in unexpected places, i.e.,
> after _edata.
>
> Signed-off-by: Ard Biesheuvel <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> ---
> v2:
> - s/DEFINE_TPS/DEFINE_RCU_TPS/
>
> kernel/rcu/tree.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index f1ba77363fbb..eec9f3d6f506 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -79,9 +79,16 @@ static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
> * the tracing userspace tools to be able to decipher the string
> * address to the matching string.
> */
> +#ifdef CONFIG_TRACING
> +#define DEFINE_RCU_TPS(sname) \
> +static const char *tp_##sname##_varname __used __tracepoint_string =
> sname##_varname;
> +#else
> +#define DEFINE_RCU_TPS(sname)
> +#endif
> +
> #define RCU_STATE_INITIALIZER(sname, sabbr, cr) \
> static char sname##_varname[] = #sname; \
> -static const char *tp_##sname##_varname __used __tracepoint_string =
> sname##_varname; \
> +DEFINE_RCU_TPS(sname) \
> struct rcu_state sname##_state = { \
> .level = { &sname##_state.node[0] }, \
> .call = cr, \
Looking at this a bit deeper (actually looking at it in the context of
the code), we can make this even better.
#ifdef CONFIG_TRACING
# define DEFINE_RCU_TPS(sname) \
static char sname##_varname[] = #sname; \
static const char *tp_##sname##_varname __used __tracepoint_string =
sname##_varname;
# define RCU_STATE_NAME(sname) sname##_varname;
#else
# define DEFINE_RCU_TPS(sname)
# define RCU_STATE_NAME(sname) __stringify(sname)
#endif
Then add:
.name = RCU_STATE_NAME(sname), \
This will get rid of the sname##_varname variable as well.
-- Steve
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