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SubjectRe: system gets stuck in a lock during boot
CC: Peter, Ingo

> Hey alright 2.6.31-rc6 booted.
>
> I must admit, I've been afraid of doing
> a git bisect for some time now. but after learning
> to do a bisect, I cant see a better solution to finding a
> bug(biggest issue I see is having a huge .config).
>
> Anyways the culprit for my issue is this commit:
>
> af6af30c0fcd77e621638e53ef8b176bca8bd3b4
>
> reverting this on rc6 booted the machine up.
>

Thanks!

Hmm...I don't see how this commit can cause oops:

> @@ -119,11 +119,9 @@ struct ftrace_event_call {
> void *filter;
> void *mod;
>
> -#ifdef CONFIG_EVENT_PROFILE
> - atomic_t profile_count;
> - int (*profile_enable)(struct ftrace_event_call *);
> - void (*profile_disable)(struct ftrace_event_call *);
> -#endif
> + atomic_t profile_count;
> + int (*profile_enable)(struct ftrace_event_call *);
> + void (*profile_disable)(struct ftrace_event_call *);

In your .config, CONFIG_EVENT_PROFILE=y, so this change makes
no difference.

> };
>
> #define MAX_FILTER_PRED 32
> diff --git a/kernel/trace/trace_event_profile.c b/kernel/trace/trace_event_profil
> index 5b5895a..11ba5bb 100644
> --- a/kernel/trace/trace_event_profile.c
> +++ b/kernel/trace/trace_event_profile.c
> @@ -14,7 +14,7 @@ int ftrace_profile_enable(int event_id)
>
> mutex_lock(&event_mutex);
> list_for_each_entry(event, &ftrace_events, list) {
> - if (event->id == event_id) {
> + if (event->id == event_id && event->profile_enable) {

You will run into this hunk only when you run the perf tool,
so should have nothing to do with the boot failure.

> ret = event->profile_enable(event);
> break;
> }
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 23d2972..e75276a 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -940,7 +940,7 @@ event_create_dir(struct ftrace_event_call *call, struct dentr
> entry = trace_create_file("enable", 0644, call->dir, call,
> enable);
>
> - if (call->id)
> + if (call->id && call->profile_enable)

We do an extra check on ->profile_enable, shouldn't cause bug..

> entry = trace_create_file("id", 0444, call->dir, call,
> id);

Any way, I don't think this commit does the right thing:

- If CONFIG_EVENT_PROFILE=y, we'll create events/<dir>/<event>/id,
except events/ftrace/<event>/id.

- if CONFIG_EVENT_PROFILE=n, there's no 'id' file at all!

I think it's better to skip ftrace/ dir in perf tool code, instead of
skipping creating id files in ftrace code.

can you try this patch:

---
include/linux/ftrace_event.h | 2 ++
kernel/trace/trace_events.c | 2 +-
tools/perf/util/parse-events.c | 8 +++++++-
3 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index a81170d..398c925 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -121,9 +121,11 @@ struct ftrace_event_call {
void *filter;
void *mod;

+#ifdef CONFIG_EVENT_PROFILE
atomic_t profile_count;
int (*profile_enable)(struct ftrace_event_call *);
void (*profile_disable)(struct ftrace_event_call *);
+#endif
};

#define MAX_FILTER_PRED 32
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index e75276a..23d2972 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -940,7 +940,7 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
entry = trace_create_file("enable", 0644, call->dir, call,
enable);

- if (call->id && call->profile_enable)
+ if (call->id)
entry = trace_create_file("id", 0444, call->dir, call,
id);

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 0441784..1077ebd 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -113,13 +113,19 @@ static unsigned long hw_cache_stat[C(MAX)] = {
[C(BPU)] = (CACHE_READ),
};

+static int is_tp_subsystem(struct dirent *sys_dir)
+{
+ return !!strcmp(sys_dir->d_name, "ftrace");
+}
+
#define for_each_subsystem(sys_dir, sys_dirent, sys_next, file, st) \
while (!readdir_r(sys_dir, &sys_dirent, &sys_next) && sys_next) \
if (snprintf(file, MAXPATHLEN, "%s/%s", debugfs_path, \
sys_dirent.d_name) && \
(!stat(file, &st)) && (S_ISDIR(st.st_mode)) && \
(strcmp(sys_dirent.d_name, ".")) && \
- (strcmp(sys_dirent.d_name, "..")))
+ (strcmp(sys_dirent.d_name, "..")) && \
+ (is_tp_subsystem(&sys_dirent)))

static int tp_event_has_id(struct dirent *sys_dir, struct dirent *evt_dir)
{



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