Messages in this thread | | | Date | Mon, 15 Mar 1999 13:28:27 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: [patch] recover lost ticks |
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On Mon, 15 Mar 1999, Andrea Arcangeli wrote:
> If the tsc goes as hell gettimeofday will die too, and the TSC is > explicity declared from Intel as a really safely trustable thing, so if > the TSC will die I expect many other part of the CPU to die too.
(i only pointed out that TSC bugs/inconsistencies (which happened in the past) now might have yet another side-effect. [there was a robustness claim])
> And maybe somebody may really intentionally take the cpu clied for more > than 10msec for some strange usage.
(do you know about any such legitimate use. I've used such things myself in the APIC code, it's not legitimate and i've fixed it.)
> Since we'll printk a message anyway and so we have just increased the > complexity of the code anyway, so why not to also recover the lost tick in > a slow path as I do?
(You have added 30 lines of code, i've removed 20. Thats a 50 lines difference.)
> >maintain piece of code to 'fix' the symptom of a fundamentally broken and > >rare case, instead of just detecting and fixing the real reason. > > I am not fixing the symptom, I am recovering the bug at runtime kprinting > the useful information as in your patch but with the difference that then > I am allowing the machine to run fine until the problem will get fixed > (and to get it fixed you may need to wait some time like in the scsi > code).
the SCSI case is pure paranoia and an unmaintained subsystem. Fixing (one of ) the effects of overlong cli() just delays the real fix. (why should we bother fixing them when system time runs just fine) Some other side-effects of overlong clis, apart from lost timer ticks: lost characters on the serial line, lost keyboard events. If someone doing strange things can live with these other effects, he sure can live with lost timer ticks as well.
-- mingo
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