(2013/08/27 17:07), Namhyung Kim wrote: > Hi Steven, > > On Thu, 22 Aug 2013 21:08:30 -0400, Steven Rostedt wrote: >> On Fri, 23 Aug 2013 07:57:15 +0800 >> "zhangwei(Jovi)" <jovi.zhang...@huawei.com> wrote: >> >> >>>> >>>> What about creating a per cpu buffer when uprobes are registered, and >>>> delete them when they are finished? Basically what trace_printk() does >>>> if it detects that there are users of trace_printk() in the kernel. >>>> Note, it does not deallocate them when finished, as it is never >>>> finished until reboot ;-) >>>> >>>> -- Steve >>>> >>> I also thought out this approach, but the issue is we cannot fetch user >>> memory into per-cpu buffer, because use per-cpu buffer should under >>> preempt disabled, and fetching user memory could sleep. >> >> Actually, we could create a per_cpu mutex to match the per_cpu buffers. >> This is not unlike what we do in -rt. >> >> int cpu; >> struct mutex *mutex; >> void *buf; >> >> >> /* >> * Use per cpu buffers for fastest access, but we might migrate >> * So the mutex makes sure we have sole access to it. >> */ >> >> cpu = raw_smp_processor_id(); >> mutex = per_cpu(uprobe_cpu_mutex, cpu); >> buf = per_cpu(uprobe_cpu_buffer, cpu); >> >> mutex_lock(mutex); >> store_trace_args(..., buf,...); >> mutex_unlock(mutex); >> > > Great! I'll go with this approach. Is it OK to you, Masami?
Yeah, it also seems to work. Please feel free to try it :) Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- 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/
