On Tue, Dec 04, 2018 at 03:04:23PM -0800, Paul E. McKenney wrote: > On Tue, Dec 04, 2018 at 02:24:13PM -0800, Josh Triplett wrote: > > On Tue, Dec 04, 2018 at 02:09:42PM -0800, tip-bot for Paul E. McKenney > > wrote: > > > --- a/tools/testing/selftests/rcutorture/bin/mkinitrd.sh > > > +++ b/tools/testing/selftests/rcutorture/bin/mkinitrd.sh > > > @@ -39,9 +39,22 @@ mkdir $T > > > > > > cat > $T/init << '__EOF___' > > > #!/bin/sh > > > +# Run in userspace a few milliseconds every second. This helps to > > > +# exercise the NO_HZ_FULL portions of RCU. > > > while : > > > do > > > - sleep 1000000 > > > + q= > > > + for i in \ > > > + a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \ > > > + a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \ > > > + a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \ > > > + a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \ > > > + a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \ > > > + a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a > > > > Ow. If there's no better way to do this, please do at least comment how > > many 'a's > > this is. (And why 186, exactly?) > > Yeah, that is admittedly a bit strange. The reason for 186 occurrences of > "a" to one-time calibration, measuring a few millisecond's worth of delay. > > > Please also consider calibrating the delay loop as you do in the C code. > > Good point. And a quick web search finds me "date '+%s%N'", which gives > me nanoseconds since the epoch. I probably don't want to do a 2038 to > myself (after all, I might still be alive then), so I should probably try > to make something work with "date '+%N'". Or use something like this: > > $ date '+%4N'; date '+%4N';date '+%4N'; date '+%4N' > 6660 > 6685 > 6697 > 6710 > > Ah, but that means I need to add the "date" command to my initrd, doesn't > it? And calculation requires either bash or the "test" command. And it > would be quite good to restrict this to what can be done with Bourne shell > built-in commands, since a big point of this is to maintain a small-sized > initrd. :-/
Sure, and I'm not suggesting adding commands to the initrd, hence my mention of "If there's no better way". > So how about the following patch, which attempts to explain the situation? That would help, but please also consider consolidating with something like a10="a a a a a a a a a a" to make it more readable (and perhaps rounding up to 200 for simplicity). - Josh
