Messages in this thread | | | Date | Fri, 19 Jul 2013 14:21:04 +0900 | From | Masami Hiramatsu <> | Subject | Re: Re: [RFC PATCH V2] tracing: Check f_dentry before accessing event_file/call in inode->i_private |
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(2013/07/18 23:51), Oleg Nesterov wrote: > On 07/18, Masami Hiramatsu wrote: >> >> (2013/07/17 23:51), Oleg Nesterov wrote: >>> Well, perhaps you are right... But this TRACE_EVENT_FL_REF_MASK code >>> is new too, it is not that we only need a small fixlets to finish it. >> >> Would you mean that TRACE_EVENT_FL_REF_MASK may also have some problems? > > It was you who initially pointed that it does have problems ;) > > And, _afaics_ your patch which tries to fix this problem is not > exactly correct.
Hm,
> It removes trace_array_get/put from tracing_open_generic_file() and > tracing_release_generic_file(). This assumes that "call->flags++" is > enough, but it is not.
No, it replaces trace_array_get/put with ftrace_event_file_get/put which calls trace_array_get/put inside. (Just one point, previous ftrace_event_file_get has a racy point when it does tr->ref++, it should be fixed.)
> Yes, the next patch adds the "flags & TRACE_EVENT_FL_REF_MASK" check > into trace_remove_event_call() path. But this is still racy wrt > instance_delete() unless I missed something. > > IOW, I believe that either .open() should do trace_array_get(), or > __trace_remove_event_dirs() needs another for-each-file loop which > checks file->call->flags & TRACE_EVENT_FL_REF_MASK.
Agreed :)
>>> So I think that it makes sense to discuss the alternatives before we >>> decide what exactly we should do. >> >> Your approach is also interesting for me, indeed. However, it is so >> different from current one. I think you should clarify what bug you >> would like to solve and how. > > The same bugs which Steven's 1/4 tries to solve ;)
OK, let me confirm that, would you mean we still need 2/4 - 4/4?
Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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