On Thu, Aug 10, 2023 at 10:55:16AM -0700, Paul E. McKenney wrote: > On Wed, Aug 09, 2023 at 02:45:44PM -0700, Guenter Roeck wrote: > > On 8/9/23 13:39, Joel Fernandes wrote: > > > On Wed, Aug 9, 2023 at 4:38 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > > > > > > > On 8/9/23 13:14, Joel Fernandes wrote: > > > > > On Wed, Aug 09, 2023 at 12:25:48PM -0700, Guenter Roeck wrote: > > > > > > On Wed, Aug 09, 2023 at 02:35:59PM -0400, Joel Fernandes wrote: > > > > > > > On Wed, Aug 9, 2023 at 12:18 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > On 8/9/23 06:53, Joel Fernandes wrote: > > > > > > > > > On Wed, Aug 09, 2023 at 12:40:36PM +0200, Greg Kroah-Hartman wrote: > > > > > > > > > > This is the start of the stable review cycle for the 5.15.126 release. > > > > > > > > > > There are 92 patches in this series, all will be posted as a response > > > > > > > > > > to this one. If anyone has any issues with these being applied, please > > > > > > > > > > let me know. > > > > > > > > > > > > > > > > > > > > Responses should be made by Fri, 11 Aug 2023 10:36:10 +0000. > > > > > > > > > > Anything received after that time might be too late. > > > > > > > > > > > > > > > > > > > > The whole patch series can be found in one patch at: > > > > > > > > > > https://www.kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.15.126-rc1.gz > > > > > > > > > > or in the git tree and branch at: > > > > > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.15.y > > > > > > > > > > and the diffstat can be found below. > > > > > > > > > > > > > > > > > > Not necesscarily new with 5.15 stable but 3 of the 19 rcutorture scenarios > > > > > > > > > hang with this -rc: TREE04, TREE07, TASKS03. > > > > > > > > > > > > > > > > > > 5.15 has a known stop machine issue where it hangs after 1.5 hours with cpu > > > > > > > > > hotplug rcutorture testing. Me and tglx are continuing to debug this. The > > > > > > > > > issue does not show up on anything but 5.15 stable kernels and neither on > > > > > > > > > mainline. > > > > > > > > > > > > > > > > > > > > > > > > > Do you by any have a crash pattern that we could possibly use to find the crash > > > > > > > > in ChromeOS crash logs ? No idea if that would help, but it could provide some > > > > > > > > additional data points. > > > > > > > > > > > > > > The pattern shows as a hard hang, the system is unresponsive and all CPUs > > > > > > > are stuck in stop_machine. Sometimes it recovers on its own from the > > > > > > > hang and then RCU immediately gives stall warnings. It takes 1.5 hour > > > > > > > to reproduce and sometimes never happens for several hours. > > > > > > > > > > > > > > It appears related to CPU hotplug since gdb showed me most of the CPUs > > > > > > > are spinning in multi_cpu_stop() / stop machine after the hang. > > > > > > > > > > > > > > > > > > > Hmm, we do see lots of soft lockups with multi_cpu_stop() in the backtrace, > > > > > > but not with v5.15.y but with v5.4.y. The actual hang is in stop_machine_yield(). > > > > > > > > > > Interesting. It looks similar as far as the stack dump in gdb goes, here are > > > > > the stacks I dumped with the hang I referred to: > > > > > https://paste.debian.net/1288308/ > > > > > > > > > > > > > That link gives me "Entry not found". > > > > > > Yeah that was weird. Here it is again: https://pastebin.com/raw/L3nv1kH2 > > > > I found a couple of crash reports from chromeos-5.10, one of them complaining > > about RCU issues. I sent you links via IM. Nothing from 5.15 or later, though. > > Is the crash showing the eternally refiring timer fixed by this commit? > > 53e87e3cdc15 ("timers/nohz: Last resort update jiffies on nohz_full IRQ entry") Ah I was just replying, I have been seeing really good results after applying the following 3 commits since yesterday: 53e87e3cdc15 ("timers/nohz: Last resort update jiffies on nohz_full IRQ entry") 5417ddc1cf1f ("timers/nohz: Switch to ONESHOT_STOPPED in the low-res handler when the tick is stopped") a1ff03cd6fb9 ("tick: Detect and fix jiffies update stall") 5417ddc1cf1f also mentioned a "tick storm" which is exactly what I was seeing. I did a lengthy test and everything is looking good. I'll send these out to the stable list. thanks, - Joel
