Messages in this thread |  | | Date | Wed, 21 May 2025 07:05:09 -0600 | | Subject | Re: printk NMI splat on boot | | From | Jens Axboe <> |
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On 5/21/25 12:06 AM, Paul E. McKenney wrote: > On Tue, May 20, 2025 at 02:41:40PM -0600, Jens Axboe wrote: >> On 5/20/25 2:18 PM, Jens Axboe wrote: >>>> What values are you using for CONFIG_RCU_EXP_CPU_STALL_TIMEOUT and >>>> CONFIG_RCU_CPU_STALL_TIMEOUT? >>> >>> CONFIG_RCU_CPU_STALL_TIMEOUT=21 >>> CONFIG_RCU_EXP_CPU_STALL_TIMEOUT=2 >> >> This was =20 btw, guess it could cut a bit too much... > > Just confirming that setting CONFIG_RCU_EXP_CPU_STALL_TIMEOUT to two > milliseconds is more than a bit on the aggressive side. ;-)
Sorry guess I wasn't clear - I had pasted in =2, but the setting in my config was =20.
> Setting it to 20 milliseconds is OK for smartphone-class devices, but > to the best of my knowledge, setting it less than 21 seconds (as in > 21,000 milliseconds) has not been tested on any other platform. > >> Changed them to: >> >> CONFIG_RCU_CPU_STALL_TIMEOUT=100 >> CONFIG_RCU_EXP_CPU_STALL_TIMEOUT=0 >> >> and complaining is gone. > > This makes it take the default, which in this case would be the specified > CONFIG_RCU_CPU_STALL_TIMEOUT value of 100 seconds. Which is an unusually > long timeout -- mainline these days is 21 seconds and some distros still > use the old value of 60 seconds.
IMHO the settings for these are very odd. Which I guess is fine for debugging kind of infrastructure, but fairly nonsensical in any case. But not really that important - looks like RCU_EXP_CPU_STALL_TIMEOUT has a default of '0' so not sure how on earth I ended up with 20 in that one. Most likely from not reading the help entry and hence setting it similarly to RCU_CPU_STALL_TIMEOUT.
-- Jens Axboe
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