On 06/25, zhangwei(Jovi) wrote: > > We cannot unregister trace_uprobe when trace_uprobe is in use, > otherwise resource will leak. > > Just return -EBUSY if user want to unregister a trace_uprobe > which in use.
Hmm. Afaics, this is not that simple. This patch copies the similar logic from trace_kprobe.c. I'll recheck later but so far I strongly believe that code is wrong. So please forget about trace_uprobe.c for the moment. Let's look at release_all_trace_probes(). It checks trace_probe_is_enabled(), but how can we trust this check? We can race with enable_trace_probe() which is going to set TP_FLAG_TRACE/TP_FLAG_PROFILE. And no, we can't change enable_trace_probe() to take probe_lock, this can ABBA with unregister_trace_probe() called under this lock because of trace_remove_event_call() which takes event_mutex. At the same time, the fact that trace_remove_event_call() takes event_mutex can probably help, because __trace_remove_event_call() should do TRACE_REG_UNREGISTER and this should serialize us with TRACE_REG_REGISTER. But TRACE_REG_PERF_REGISTER is different, and does not look safe. In fact I suspect there are more serious problems, but I need to recheck. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
