Messages in this thread | | | Date | Tue, 14 Apr 2009 08:53:03 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] tracing/lockdep: turn lock->name into an array |
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* KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> Hi > > > Impact: allow filtering by lock name / fix module tracing > > > > Currently, the "lock acquired" event is traced using a TRACE_EVENT. > > But we can't use the char * type for the name without risking to > > dereference a freed pointer. A lock name can come from a module > > towards lockdep and it is risky to only store its address because we > > defer its name printing. > > When released lockdep string table? I guess it only happend at > module unloading. if so, we should consider to make delayed string > table freeing at module unloading. > > My point is, module unloading is rare event. thus meking pointer > safe mechanism widely avoid string copy. > > IOW, if not, ringbuffer is filled tons string. it kill the merit > of binary buffer and current design.
We could zap all pending trace entries on module unload (it is a rare operation). That would indeed make a whole category of symbol-alike string pointers safe to be passed by value.
Ingo
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