The patch titled Subject: watchdog/softlockup:Fix incorrect CPU utilization output during softlockup has been added to the -mm mm-nonmm-unstable branch. Its filename is watchdog-softlockup-fix-incorrect-cpu-utilization-output-during-softlockup.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-softlockup-fix-incorrect-cpu-utilization-output-during-softlockup.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: ZhenguoYao Subject: watchdog/softlockup:Fix incorrect CPU utilization output during softlockup Date: Tue, 12 Aug 2025 16:25:10 +0800 Since we use 16-bit precision, the raw data will undergo integer division, which may sometimes result in data loss. This can lead to slightly inaccurate CPU utilization calculations. Under normal circumstances, this isn't an issue. However, when CPU utilization reaches 100%, the calculated result might exceed 100%. For example, with raw data like the following: sample_period 400000134 new_stat 83648414036 old_stat 83247417494 sample_period=400000134/2^24=23 new_stat=83648414036/2^24=4985 old_stat=83247417494/2^24=4961 util=105% Below log will output： CPU#3 Utilization every 0s during lockup: #1: 0% system, 0% softirq, 105% hardirq, 0% idle #2: 0% system, 0% softirq, 105% hardirq, 0% idle #3: 0% system, 0% softirq, 100% hardirq, 0% idle #4: 0% system, 0% softirq, 105% hardirq, 0% idle #5: 0% system, 0% softirq, 105% hardirq, 0% idle To avoid confusion, we enforce a 100% display cap when calculations exceed this threshold. Link: https://lkml.kernel.org/r/20250812082510.32291-1-yaozhenguo@jd.com Signed-off-by: ZhenguoYao Cc: Bitao Hu Cc: Li Huafei Cc: Max Kellermann Cc: Thomas Gleinxer Signed-off-by: Andrew Morton --- kernel/watchdog.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/kernel/watchdog.c~watchdog-softlockup-fix-incorrect-cpu-utilization-output-during-softlockup +++ a/kernel/watchdog.c @@ -444,6 +444,13 @@ static void update_cpustat(void) old_stat = __this_cpu_read(cpustat_old[i]); new_stat = get_16bit_precision(cpustat[tracked_stats[i]]); util = DIV_ROUND_UP(100 * (new_stat - old_stat), sample_period_16); + /* Since we use 16-bit precision, the raw data will undergo + * integer division, which may sometimes result in data loss, + * and then result might exceed 100%. To avoid confusion, + * we enforce a 100% display cap when calculations exceed this threshold. + */ + if (util > 100) + util = 100; __this_cpu_write(cpustat_util[tail][i], util); __this_cpu_write(cpustat_old[i], new_stat); } _ Patches currently in -mm which might be from yaozhenguo1@gmail.com are watchdog-softlockup-fix-wrong-output-when-watchdog_thresh-3.patch watchdog-softlockup-fix-incorrect-cpu-utilization-output-during-softlockup.patch