Messages in this thread | | | Date | Fri, 2 Oct 2009 14:13:57 +0200 | Subject | Re: Possible bug in ftrace_profile_enable_event | From | Frédéric Weisbecker <> |
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2009/10/1 Paul Mackerras <paulus@samba.org>: > I was looking through kernel/trace/trace_event_profile.c and I saw > this code: > > static int ftrace_profile_enable_event(struct ftrace_event_call *event) > { > char *buf; > int ret = -ENOMEM; > > if (atomic_inc_return(&event->profile_count)) > return 0; > > if (!total_profile_count++) { > buf = (char *)alloc_percpu(profile_buf_t); > if (!buf) > goto fail_buf; > > rcu_assign_pointer(trace_profile_buf, buf); > > buf = (char *)alloc_percpu(profile_buf_t); > if (!buf) > goto fail_buf_nmi; > > rcu_assign_pointer(trace_profile_buf_nmi, buf); > } > > ret = event->profile_enable(); > if (!ret) > return 0; > > kfree(trace_profile_buf_nmi); > fail_buf_nmi: > kfree(trace_profile_buf); > fail_buf: > total_profile_count--; > > ... > > So we only allocate trace_profile_buf and trace_profile_buf_nmi if > total_profile_count was zero on entry, but if we get an error returned > from event->profile_enable(), we free them both unconditionally, > regardless of the value of total_profile_count. That seems wrong. Is > there a subtle reason why that is the right thing to do?
Oh right. Good catch. I'll fix that soon.
> > (Also, is kfree the appropriate counterpart to alloc_percpu?)
No indeed. That said it looks harmless for now because percpu_free seem to just roughly wrap kfree. But its implementation may change later, so I'll fix that too.
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