On Fri, Mar 13, 2009 at 10:39:36AM +0000, Lai Jiangshan wrote:
> Commit-ID: e94142a67f8bad494c593f0a07c9fc2fbec98c0e
> Gitweb: http://git.kernel.org/tip/e94142a67f8bad494c593f0a07c9fc2fbec98c0e
> Author: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> AuthorDate: Fri, 13 Mar 2009 17:51:27 +0800
> Commit: Ingo Molnar <mingo@xxxxxxx>
> CommitDate: Fri, 13 Mar 2009 11:36:20 +0100
>
> ftrace: remove struct list_head from struct dyn_ftrace
>
> Impact: save memory
>
> The struct dyn_ftrace table is very large, this patch will save
> about 50%.
>
> Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> Cc: Steven Rostedt <srostedt@xxxxxxxxxx>
> LKML-Reference: <49BA2C9F.8020009@xxxxxxxxxxxxxx>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
>
>
> ---
> include/linux/ftrace.h | 1 -
> kernel/trace/ftrace.c | 14 ++++++++------
> 2 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index c146c10..9d598bb 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -145,7 +145,6 @@ enum {
> };
>
> struct dyn_ftrace {
> - struct list_head list;
> unsigned long ip; /* address of mcount call-site */
> unsigned long flags;
> struct dyn_arch_ftrace arch;
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index bf78a4c..90d5729 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -272,7 +272,7 @@ enum {
>
> static int ftrace_filtered;
>
> -static LIST_HEAD(ftrace_new_addrs);
> +static struct dyn_ftrace *ftrace_new_addrs;
>
> static DEFINE_MUTEX(ftrace_regex_lock);
>
> @@ -409,8 +409,8 @@ ftrace_record_ip(unsigned long ip)
> return NULL;
>
> rec->ip = ip;
> -
> - list_add(&rec->list, &ftrace_new_addrs);
> + rec->flags = (unsigned long)ftrace_new_addrs;
> + ftrace_new_addrs = rec;
But... you are overwritting all the ftrace flags infrastructure by
using it as a list pointer.
This is breaking dynamic tracing.
>
> return rec;
> }
> @@ -716,19 +716,21 @@ unsigned long ftrace_update_tot_cnt;
>
> static int ftrace_update_code(struct module *mod)
> {
> - struct dyn_ftrace *p, *t;
> + struct dyn_ftrace *p;
> cycle_t start, stop;
>
> start = ftrace_now(raw_smp_processor_id());
> ftrace_update_cnt = 0;
>
> - list_for_each_entry_safe(p, t, &ftrace_new_addrs, list) {
> + while (ftrace_new_addrs) {
>
> /* If something went wrong, bail without enabling anything */
> if (unlikely(ftrace_disabled))
> return -1;
>
> - list_del_init(&p->list);
> + p = ftrace_new_addrs;
> + ftrace_new_addrs = (struct dyn_ftrace *)p->flags;
> + p->flags = 0L;
>
> /* convert record (i.e, patch mcount-call with NOP) */
> if (ftrace_code_disable(mod, p)) {
> --
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