On Tue, Mar 22, 2022 at 11:49:09AM +0100, Frederic Weisbecker wrote: > On Mon, Mar 21, 2022 at 08:57:46AM -0700, Paul E. McKenney wrote: > > On Mon, Mar 21, 2022 at 11:46:28PM +0800, Zhouyi Zhou wrote: > > > Hi Paul and Willy > > > > > > I can reproduce the bug. Following is what I do: > > > 1.1 git clone https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/torvalds/linux.git > > > 1.2 cd linux > > > 1.3 cp http://154.223.142.244/20220321/config-20220321 to .config > > > 1.4 make vmlinux -j 16 > > > 1.5 kvm -smp 4 -net none -serial file:/tmp/console.log -m 512 > > > -kernel vmlinux -append "console=ttyS0" > > > 1.6 the /tmp/console.log is uploaded to > > > http://154.223.142.244/20220321/console.log > > > > > > 2.1 wget https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/torvalds/linux.git/snapshot/linux-5.17-rc6.tar.gz > > > 2.2 - 2.6 the result is similar. > > > > > > I am very interested in this topic. > > > Could you please give me about a week to make a full understand of the > > > meaning of the warning, and try the fixes one by one, and > > > find out what happens? > > > > Works for me! The eventual fix likely involves some version of Valentin > > Schneider's patchset that provides APIs that allow RCU to detect the > > current preemption state. Which can change at runtime. A prototype of > > this patch is on -rcu here: > > > > 2436ee0b4cea ("EXP preempt/dynamic: Introduce preempt mode accessors") > > > > It is entirely possible that the fix might need to go to mainline sooner > > rather than later. > > I guess it's possible to do that but that patch alone shouldn't fix anything. > Also, what is the issue exactly? :-) > I can't rewind far enough the conversation. I am no longer entirely sure myself. I initially thought that this was the issue where CONFIG_PREEMPT_DYNAMIC=y was confusing Tasks RCU, but Zhouyi can make something happen in current -rcu. Thanx, Paul
