Messages in this thread | | | Subject | Re: [PATCH 1/2] random: Omit double-printing ratelimit messages | From | Dmitry Safonov <> | Date | Fri, 11 May 2018 13:41:03 +0100 |
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On Thu, 2018-05-10 at 23:51 -0400, Theodore Y. Ts'o wrote: > On Thu, May 10, 2018 at 08:50:07PM +0100, Dmitry Safonov wrote: > > random uses __ratelimit() which calls ___ratelimit() with a > > function > > name. Depending on !RATELIMIT_MSG_ON_RELEASE it prints how many > > messages were suppressed every ratelimit interval (1 second for > > random) > > and flushes ratelimit_state::missed: > > So the thing about the ratelimit system is that if you have a burst > of > 1,000,000 within the one second burst window, and then nothing ever > again, you will never see a message accounting for those 1,000,000 > "callbacks" (which is a terrible wording; it just confuses people). > > If you have a burst of 1,000,000 calls to ratelimit, and then a month > goes by, and *then* a single call to __ratelimit is called by printk, > only *the* does the message about the suppressed "callback" get > printed.
Yes, if the initialization time of driver is lesser than a second. If it's 1.1 sec - you'll have prints from ___ratelimit() and from your driver too. And they differ in format.
> So in the case of the random driver, once the random driver is fully > intialized, there will never be a call to __ratelimit() for the > urandom ratelimit structures, so we manually print out the final > number of suppressed message so there is proper accounting for them.
So, there is this flag, AFAICS, which perfectly fits your purpose RATELIMIT_MSG_ON_RELEASE which will omit printing how many messages were suppressed every interval of ___ratelimit(). And that will allow you to print total in the end.
> It is not a double-count. If we didn't do that, those suppressed > warnings would never be mentioned by the kernel.
Yeah, but what you print is not total sum, it's since the last interval because without mentioned flag ___ratelimit() will flush missed counter and print "suppressed" message. They might even double if say other proccess has called get_random_bytes() got to ___ratelimit() and got preempted. This thread finishes initializing random driver and prints this not-proper-sum statistics, and when the code flow is back in the first context, it will print statistics again from ___ratelimit() function.
-- Thanks, Dmitry
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