On 2017/2/25 17:51, Peter Zijlstra wrote: > On Sat, Feb 25, 2017 at 04:10:37PM +0800, Tan Xiaojun wrote: > >> Recently I was using perf_fuzzer for testing in Hisilicon >> D03/D05(arm64, linux-4.10-rc1). >> >> As we know perf_fuzzer will write a random value to procfs interface >> of perf event(like sysctl_perf_cpu_time_max_percent). The value may be >> 0 or 100, and I get logs like below: >> >> ---------------------------------- >> [ 4046.358811] perf: Dynamic interrupt throttling disabled, can hang your system! >> ---------------------------------- >> >> Most of the time, there is no problem, and the perf_fuzzer test can >> end without any warings or errors. But there is a small probability >> that triggers the RCU and watchdog (The log is attached at the end). >> It hungs after local_irq_enable() in __do_softirq. >> >> I think this is due to the dynamic interrupt throttling disabled and >> too many hardware interruptions come. So I limit the >> sysctl_perf_cpu_time_max_percent can only be set 1 to 99 in the kernel >> codes. I test more than 20 times in D03, and there are no errors or >> warnings in the test. >> >> So I want to ask: >> >> 1)Is it a problem or not? (It has already given you a warning.) >> >> 2)If it is, where we will fix it more appropriate, perf_fuzzer(not set >> 0 or 100) or kernel(limit 1 to 99), or maybe it is the bug of >> hardware(too many hardware interruptions)? > > I think the best would be if the fuzzer would not set 0,100, those are > clearly 'unsafe' settings and you pretty much get to keep the pieces. > > I would like to preserve these settings for people that 'know' what > they're doing and are willing to take the risk, but clearly, when you > take the guard-rails off, things can come apart. > OK. It makes sense, I agree. Thank you for your answer. Xiaojun. > . > -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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