kernel/linux.git/fs/proc/stat.c, branch v7.2-rc1

Merge tag 'timers-nohz-2026-06-13' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip

2026-06-15T08:18:52+00:00

Pull NOHZ updates from Thomas Gleixner: - Fix a long standing TOCTOU in get_cpu_sleep_time_us() - Make the CPU offline NOHZ handling more robust by disabling NOHZ on the outgoing CPU early instead of creating unneeded state which needs to be undone. - Unify idle CPU time accounting instead of having two different accounting mechanisms. These two different mechanisms are not really independent, but the different properties can in the worst case cause that gloabl idle time can be observed going backwards. - Consolidate the idle/iowait time retrieval interfaces instead of converting back and forth between them. - Make idle interrupt time accounting more robust. The original code assumes that interrupt time accouting is enabled and therefore stops elapsing idle time while an interrupt is handled in NOHZ dyntick state. That assumption is not correct as interrupt time accounting can be disabled at compile and runtime. - Fix an accounting error between dyntick idle time and dyntick idle steal time. The stolen time is not accounted and therefore idle time becomes inaccurate. The stolen time is now accounted after the fact as there is no way to predict the steal time upfront. * tag 'timers-nohz-2026-06-13' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip: sched/cputime: Handle dyntick-idle steal time correctly sched/cputime: Handle idle irqtime gracefully sched/cputime: Provide get_cpu_[idle|iowait]_time_us() off-case tick/sched: Consolidate idle time fetching APIs tick/sched: Account tickless idle cputime only when tick is stopped tick/sched: Remove unused fields tick/sched: Move dyntick-idle cputime accounting to cputime code tick/sched: Remove nohz disabled special case in cputime fetch tick/sched: Unify idle cputime accounting s390/time: Prepare to stop elapsing in dynticks-idle powerpc/time: Prepare to stop elapsing in dynticks-idle sched/cputime: Correctly support generic vtime idle time sched/cputime: Remove superfluous and error prone kcpustat_field() parameter sched/idle: Handle offlining first in idle loop tick/sched: Fix TOCTOU in nohz idle time fetch

tick/sched: Consolidate idle time fetching APIs

2026-06-02T19:27:26+00:00

Fetching the idle cputime is available through a variety of accessors all over the place depending on the different accounting flavours and needs: - idle vtime generic accounting can be accessed by kcpustat_field(), kcpustat_cpu_fetch(), get_idle/iowait_time() and get_cpu_idle/iowait_time_us() - dynticks-idle accounting can only be accessed by get_idle/iowait_time() or get_cpu_idle/iowait_time_us() - CONFIG_NO_HZ_COMMON=n idle accounting can be accessed by kcpustat_field() kcpustat_cpu_fetch(), or get_idle/iowait_time() but not by get_cpu_idle/iowait_time_us() Moreover get_idle/iowait_time() relies on get_cpu_idle/iowait_time_us() with a non-sensical conversion to microseconds and back to nanoseconds on the way. Start consolidating the APIs with removing get_idle/iowait_time() and make kcpustat_field() and kcpustat_cpu_fetch() work for all cases. Signed-off-by: Frederic Weisbecker Signed-off-by: Thomas Gleixner Tested-by: Shrikanth Hegde Link: https://patch.msgid.link/20260508131647.43868-13-frederic@kernel.org

x86/irq: Move IOAPIC misrouted and PIC/APIC error counts into irq_stats

2026-05-26T14:21:12+00:00

The special treatment of these counts is just adding extra code for no real value. The irq_stats mechanism allows to suppress output of counters, which should never happen by default and provides a mechanism to enable them for the rare case that they occur. Move the IOAPIC misrouted and the PIC/APIC error counts into irq_stats, mark them suppressed by default and update the sites which increment them. This changes the output format of 'ERR' and 'MIS' in case there are events to the regular per CPU display format and otherwise suppresses them completely. As a side effect this removes the arch_cpu_stat() mechanism from proc/stat which was only there to account for the error interrupts on x86 and missed to take the misrouted ones into account. Signed-off-by: Thomas Gleixner Tested-by: Michael Kelley Reviewed-by: Radu Rendec Link: https://patch.msgid.link/20260517194931.361942103@kernel.org

fs/procfs: Switch to irq_get_nr_irqs()

2024-10-16T19:56:59+00:00

Use the irq_get_nr_irqs() function instead of the global variable 'nr_irqs'. Prepare for changing 'nr_irqs' from an exported global variable into a variable with file scope. Signed-off-by: Bart Van Assche Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20241015190953.1266194-21-bvanassche@acm.org

proc/stat: remove arch_idle_time()

2023-04-18T23:39:33+00:00

The last (only) architecture specific arch_idle_time() implementation was removed with commit be76ea614460 ("s390/idle: remove arch_cpu_idle_time() and corresponding code"). Therefore remove the now dead code in fs/proc/stat.c as well. Link: https://lkml.kernel.org/r/20230405143452.2677172-1-hca@linux.ibm.com Signed-off-by: Heiko Carstens Cc: Alexey Dobriyan Signed-off-by: Andrew Morton

fs/proc/uptime.c: Fix idle time reporting in /proc/uptime

2021-10-05T13:51:35+00:00

/proc/uptime reports idle time by reading the CPUTIME_IDLE field from the per-cpu kcpustats. However, on NO_HZ systems, idle time is not continually updated on idle cpus, leading this value to appear incorrectly small. /proc/stat performs an accounting update when reading idle time; we can use the same approach for uptime. With this patch, /proc/stat and /proc/uptime now agree on idle time. Additionally, the following shows idle time tick up consistently on an idle machine: (while true; do cat /proc/uptime; sleep 1; done) | awk '{print $2-prev; prev=$2}' Reported-by: Luigi Rizzo Signed-off-by: Josh Don Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Eric Dumazet Link: https://lkml.kernel.org/r/20210827165438.3280779-1-joshdon@google.com

sched: Make nr_iowait() return 32-bit value

2021-05-12T19:34:15+00:00

Creating 2**32 tasks to wait in D-state is impossible and wasteful. Return "unsigned int" and save on REX prefixes. Signed-off-by: Alexey Dobriyan Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20210422200228.1423391-2-adobriyan@gmail.com

sched: Make nr_running() return 32-bit value

2021-05-12T19:34:14+00:00

Creating 2**32 tasks is impossible due to futex pid limits and wasteful anyway. Nobody has done it. Bring nr_running() into 32-bit world to save on REX prefixes. Signed-off-by: Alexey Dobriyan Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20210422200228.1423391-1-adobriyan@gmail.com

Merge tag 'time-namespace-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

2020-12-15T00:35:39+00:00

Pull time namespace updates from Christian Brauner: "When time namespaces were introduced we missed to virtualize the 'btime' field in /proc/stat. This confuses tasks which are in another time namespace with a virtualized boottime which is common in some container workloads. This contains Michael's series to fix 'btime' which Thomas asked me to take through my tree. To fix 'btime' virtualization we simply subtract the offset of the time namespace's boottime from btime before printing the stats. Note that since start_boottime of processes are seconds since boottime and the boottime stamp is now shifted according to the time namespace's offset, the offset of the time namespace also needs to be applied before the process stats are given to userspace. This avoids that processes shown by tools such as 'ps' appear as time travelers in the corresponding time namespace. Selftests are included to verify that btime virtualization in /proc/stat works as expected" * tag 'time-namespace-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: namespace: make timens_on_fork() return nothing selftests/timens: added selftest for /proc/stat btime fs/proc: apply the time namespace offset to /proc/stat btime timens: additional helper functions for boottime offset handling

proc/stat: switch to ->read_iter

2020-11-06T18:05:18+00:00

Implement ->read_iter so that splice can be used on this file. Suggested-by: Linus Torvalds Signed-off-by: Christoph Hellwig Signed-off-by: Linus Torvalds