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    SubjectRe: [RFC][PATCH 2/4] tracing: trace_remove_event_call() should fail if call/file is in use
    (2013/07/04 12:33), Steven Rostedt wrote:
    > From: Oleg Nesterov <oleg@redhat.com>
    >
    > Change trace_remove_event_call(call) to return the error if this
    > call is active. This is what the callers assume but can't verify
    > outside of the tracing locks. Both trace_kprobe.c/trace_uprobe.c
    > need the additional changes, unregister_trace_probe() should abort
    > if trace_remove_event_call() fails.
    >
    > We also check TRACE_EVENT_FL_REF_MASK to ensure that nobody opened
    > the files we are going to remove, these means that nobody can access
    > the soon-to-be-freed ftrace_event_file/call via filp->private_data.
    >
    > Link: http://lkml.kernel.org/r/20130702222359.GA27629@redhat.com

    This looks good for me ;)

    Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

    Thanks!

    >
    > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    > Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    > ---
    > include/linux/ftrace_event.h | 2 +-
    > kernel/trace/trace_events.c | 33 +++++++++++++++++++++++++++++++--
    > 2 files changed, 32 insertions(+), 3 deletions(-)
    >
    > diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
    > index 72ff2c6..bdf6bdd 100644
    > --- a/include/linux/ftrace_event.h
    > +++ b/include/linux/ftrace_event.h
    > @@ -338,7 +338,7 @@ extern int trace_define_field(struct ftrace_event_call *call, const char *type,
    > const char *name, int offset, int size,
    > int is_signed, int filter_type);
    > extern int trace_add_event_call(struct ftrace_event_call *call);
    > -extern void trace_remove_event_call(struct ftrace_event_call *call);
    > +extern int trace_remove_event_call(struct ftrace_event_call *call);
    >
    > #define is_signed_type(type) (((type)(-1)) < (type)1)
    >
    > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
    > index 90cf243..1a5547e 100644
    > --- a/kernel/trace/trace_events.c
    > +++ b/kernel/trace/trace_events.c
    > @@ -1766,16 +1766,45 @@ static void __trace_remove_event_call(struct ftrace_event_call *call)
    > destroy_preds(call);
    > }
    >
    > +static int probe_remove_event_call(struct ftrace_event_call *call)
    > +{
    > + struct trace_array *tr;
    > + struct ftrace_event_file *file;
    > +
    > + if (call->flags & TRACE_EVENT_FL_REF_MASK)
    > + return -EBUSY;
    > +
    > +#ifdef CONFIG_PERF_EVENTS
    > + if (call->perf_refcount)
    > + return -EBUSY;
    > +#endif
    > + do_for_each_event_file(tr, file) {
    > + if (file->event_call != call)
    > + continue;
    > + if (file->flags & FTRACE_EVENT_FL_ENABLED)
    > + return -EBUSY;
    > + break;
    > + } while_for_each_event_file();
    > +
    > + __trace_remove_event_call(call);
    > +
    > + return 0;
    > +}
    > +
    > /* Remove an event_call */
    > -void trace_remove_event_call(struct ftrace_event_call *call)
    > +int trace_remove_event_call(struct ftrace_event_call *call)
    > {
    > + int ret;
    > +
    > mutex_lock(&trace_types_lock);
    > mutex_lock(&event_mutex);
    > down_write(&trace_event_sem);
    > - __trace_remove_event_call(call);
    > + ret = probe_remove_event_call(call);
    > up_write(&trace_event_sem);
    > mutex_unlock(&event_mutex);
    > mutex_unlock(&trace_types_lock);
    > +
    > + return ret;
    > }
    >
    > #define for_each_event(event, start, end) \
    >


    --
    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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