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Date: Sun, 23 Aug 2009 20:07:20 -0700
From: "Justin P. Mattock" <justinmattock@...il.com>
To: Li Zefan <lizf@...fujitsu.com>
CC: Steven Rostedt <rostedt@...dmis.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...e.hu>
Subject: Re: system gets stuck in a lock during boot
Li Zefan wrote:
> 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:
>
same here, perf is not enabled at all.
before the git bisect I manually reverted all perf
and came to the conclusion the perf had nothing to do with this.
(must have missed this commit).
>
>> @@ -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.
>
I haven't really looked into perf yet, nor have it enabled.
>
>> 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..
>
maybe this has something to do with SELinux, since I saw with
the oops something with inode_do_init_dentry, and some other stuff
pertaining to SELinux(again though I'm lost as to why I'm hitting this).
>
>> 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)
> {
>
>
>
>
Alright, in the morning I try this out and let you
know what happens.
Thanks for looking at this.
Justin P. Mattock
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