On 11/01, Oleg Nesterov wrote: > > Hi Namhyung, > > Sorry if this was already discussed. But I can't really understand > the idea of this per-cpu buffer... > > On 10/29, Namhyung Kim wrote: > > > > Fetching from user space should be done in a non-atomic context. So > > use a per-cpu buffer and copy its content to the ring buffer > > atomically. Note that we can migrate during accessing user memory > > thus use a per-cpu mutex to protect concurrent accesses. > > And if the task migrates or just sleeps in page fault, another task > which hits another uprobe on the same CPU should wait. > > Why we can't simply add trace_uprobe->buffer instead? Only to save > some memory? But every uprobe is very expensive in this sense anyway.
Ah, please ignore... handler_chain() is not self-serialized, so tu->buffer needs locking/waiting too. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
