Hi, I am observing an issue with the latest 4.9 RT patch where sometimes after reboot, I see ktimersoftd is running at 100% CPU usage. Because of this, other applications on our box (our own custom applications) get stuck during their initialization (they are waiting for a semaphore to be signaled by a thread which never gets scheduled because of this ktimersoftd). I am running the latest 4.9.196+RT131 patches on a 2-core ARM platform. I have also tried with an older 4.9.82-rt61 and I have observed the same behavior. Moving to 4.14/4.19 branches is not an option for us right now unfortunately, so I cannot try this on those branches. I saw a similar issue being seen with Wireshark (mentioned at https://lore.kernel.org/patchwork/patch/931504/) and some work related to that was done and a patch was submitted by Haris: https://lkml.org/lkml/2018/6/28/581 and https://lkml.org/lkml/2018/6/28/582 I don't think the patch has made it through into the official release. I have tried incorporating his patch also but again I see the same issue. A snippet of the top command shows the following: top - 06:30:52 up 1:14, 0 users, load average: 7.00, 7.00, 6.99 Tasks: 104 total, 7 running, 97 sleeping, 0 stopped, 0 zombie %Cpu(s): 4.7 us, 13.4 sy, 0.0 ni, 43.6 id, 0.2 wa, 0.0 hi, 38.0 si, 0.0 st KiB Mem: 1025608 total, 55668 used, 969940 free, 2500 buffers KiB Swap: 0 total, 0 used, 0 free. 19668 cached Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 5 root -2 0 0 0 0 R 100.0 0.0 74:06.20 ktimersoftd/0 15423 root 20 0 2984 1760 1388 R 6.0 0.2 0:00.02 top 1 root 20 0 5124 3768 2144 S 0.0 0.4 0:06.36 systemd 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ktwork 4 root 20 0 0 0 0 R 0.0 0.0 0:00.05 ksoftirqd/0 6 root 20 0 0 0 0 R 0.0 0.0 0:00.00 kworker/0:0 Another observation is that the rescheduling interrupts on CPU 1 is very high compared to CPU 0 and increasing at a very high rate. IPI2: 35231 4341660 Rescheduling interrupts I am not sure how can I debug this further to figure out whats causing ktimersoftd to run at 100% CPU. Can you guys offer any pointers to further debug this issue? Thanks, Mukul
