Hi Boqun Feng, On Tue, Dec 08, 2020 at 10:41:31AM +0800, Boqun Feng wrote: > Hi Frederic, > > On Fri, Nov 13, 2020 at 01:13:15PM +0100, Frederic Weisbecker wrote: > > This keeps growing up. Rest assured, most of it is debug code and sanity > > checks. > > > > Boqun Feng found that holding rnp lock while updating the offloaded > > state of an rdp isn't needed, and he was right despite my initial > > reaction. The sites that read the offloaded state while holding the rnp > > lock are actually protected because they read it locally in a non > > preemptible context. > > > > So I removed the rnp lock in "rcu/nocb: De-offloading CB". And just to > > make sure I'm not missing something, I added sanity checks that ensure > > we always read the offloaded state in a safe way (3 last patches). > > > > Still passes TREE01 (but I had to fight!) > > > > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git > > rcu/nocb-toggle-v4 > > > > HEAD: 579e15efa48fb6fc4ecf14961804051f385807fe > > > > This whole series look good to me, plus I've run a test, so far > everything seems working ;-) Here is my setup for the test: > > I'm using a ARM64 guest (running on Hyper-V) to do the test, and the > guest has 8 VCPUs. The code I'm using is v5.10-rc6 + Hyper-V ARM64 guest > support [1] + your patchset (I actually did a merge from your > rcu/nocb-toggle-v5 branch, because IIUC some modification for rcutorture > is still in Paul's tree). I compiled with my normal configuration for > ARM64 Hyper-V guest plus TREE01, boot the kernel with: > > ignore_loglevel rcutree.gp_preinit_delay=3 rcutree.gp_init_delay=3 rcutree.gp_cleanup_delay=3 rcu_nocbs=0-1,3-7 > > and run rcutorture via: > > modprobe rcutorture nocbs_nthreads=8 nocbs_toggle=1000 fwd_progress=0 > > I ran the rcutorture twice, one last for a week or so and one for a day > or two and I didn't observe any problem so far. The latest test summary > is: > > [...] rcu-torture: rtc: 00000000f794686f ver: 2226396 tfle: 0 rta: 2226397 rtaf: 0 rtf: 2226385 rtmbe: 0 rtmbkf: 0/1390141 rtbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 181415346 onoff: 0/0:0/0 -1,0:-1,0 0:0 (HZ=1000) barrier: 0/0:0 read-exits: 108102 nocb-toggles: 306964:306974 > > Is there anything I'm missing for a useful test? Do you have other setup > (kernel cmdline or rcutorture parameters) that you want me to try? Thanks a lot for reviewing and testing. You seem to have tested with the right options, I have nothing better to suggest. Plus I'm glad you tested on ARM64. x86 is the only target I have tested so far.
