Messages in this thread |  | | Date | Mon, 30 Nov 2020 12:17:59 -0500 | From | Paul Gortmaker <> | Subject | Re: [PATCH 2/3] clear_warn_once: bind a timer to written reset value |
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[Re: [PATCH 2/3] clear_warn_once: bind a timer to written reset value] On 30/11/2020 (Mon 11:20) Steven Rostedt wrote:
> On Thu, 26 Nov 2020 01:30:28 -0500 > Paul Gortmaker <paul.gortmaker@windriver.com> wrote: > > > +++ b/Documentation/admin-guide/clearing-warn-once.rst > > @@ -7,3 +7,12 @@ echo 1 > /sys/kernel/debug/clear_warn_once > > > > clears the state and allows the warnings to print once again. > > This can be useful after test suite runs to reproduce problems. > > + > > +Values greater than one set a timer for a periodic state reset; e.g. > > + > > +echo 3600 > /sys/kernel/debug/clear_warn_once > > I wonder if the value should be in minutes and not seconds, otherwise, a > wrong value could possibly DoS the machine, if you were to write 2 into it. > If there were a lot of warnings in high frequency events. > > Or is dumping out a bunch of warnings every 2 seconds not be a problem?
It doesn't seem to be a problem - at least in that running a defconfig build on an otherwise out of the box common distro doesn't seem to trip any WARN or printk_once events in my testing. Of course there may be a use case out there that is doing lots of them, however.
> Anyway, would there ever be a need to have it cleared in less than 1 minute > intervals?
I don't think so - as I said in another follow up from last week:
https://lore.kernel.org/lkml/20201127174316.GA11748@windriver.com/
I'd also indicated in the above that I'd be fine with adding a minimum of 1m if people feel better about that. Also maybe moving the units to minutes instead of seconds helps implicitly convey the intended use better -- i.e. "don't be smashing on this every second" -- maybe that was your point as well - and I'd agree with that.
Paul. --
> > -- Steve > > > > + > > +will establish an hourly state reset, effectively turning WARN_ONCE > > +into a long period rate-limited warning.
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