user/sven/linux.git/kernel/time, branch v5.18.13

fix race between exit_itimers() and /proc/pid/timers

2022-07-22T08:21:18Z

commit d5b36a4dbd06c5e8e36ca8ccc552f679069e2946 upstream. As Chris explains, the comment above exit_itimers() is not correct, we can race with proc_timers_seq_ops. Change exit_itimers() to clear signal->posix_timers with ->siglock held. Cc: Reported-by: chris@accessvector.net Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

tick/nohz: unexport __init-annotated tick_nohz_full_setup()

2022-07-02T14:44:55Z

commit 2390095113e98fc52fffe35c5206d30d9efe3f78 upstream. EXPORT_SYMBOL and __init is a bad combination because the .init.text section is freed up after the initialization. Hence, modules cannot use symbols annotated __init. The access to a freed symbol may end up with kernel panic. modpost used to detect it, but it had been broken for a decade. Commit 28438794aba4 ("modpost: fix section mismatch check for exported init/exit sections") fixed it so modpost started to warn it again, then this showed up: MODPOST vmlinux.symvers WARNING: modpost: vmlinux.o(___ksymtab_gpl+tick_nohz_full_setup+0x0): Section mismatch in reference from the variable __ksymtab_tick_nohz_full_setup to the function .init.text:tick_nohz_full_setup() The symbol tick_nohz_full_setup is exported and annotated __init Fix this by removing the __init annotation of tick_nohz_full_setup or drop the export. Drop the export because tick_nohz_full_setup() is only called from the built-in code in kernel/sched/isolation.c. Fixes: ae9e557b5be2 ("time: Export tick start/stop functions for rcutorture") Reported-by: Linus Torvalds Signed-off-by: Masahiro Yamada Tested-by: Paul E. McKenney Signed-off-by: Linus Torvalds Cc: Thomas Backlund Signed-off-by: Greg Kroah-Hartman

timekeeping: Add raw clock fallback for random_get_entropy()

2022-05-30T07:24:04Z

commit 1366992e16bddd5e2d9a561687f367f9f802e2e4 upstream. The addition of random_get_entropy_fallback() provides access to whichever time source has the highest frequency, which is useful for gathering entropy on platforms without available cycle counters. It's not necessarily as good as being able to quickly access a cycle counter that the CPU has, but it's still something, even when it falls back to being jiffies-based. In the event that a given arch does not define get_cycles(), falling back to the get_cycles() default implementation that returns 0 is really not the best we can do. Instead, at least calling random_get_entropy_fallback() would be preferable, because that always needs to return _something_, even falling back to jiffies eventually. It's not as though random_get_entropy_fallback() is super high precision or guaranteed to be entropic, but basically anything that's not zero all the time is better than returning zero all the time. Finally, since random_get_entropy_fallback() is used during extremely early boot when randomizing freelists in mm_init(), it can be called before timekeeping has been initialized. In that case there really is nothing we can do; jiffies hasn't even started ticking yet. So just give up and return 0. Suggested-by: Thomas Gleixner Signed-off-by: Jason A. Donenfeld Reviewed-by: Thomas Gleixner Cc: Arnd Bergmann Cc: Theodore Ts'o Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman

timekeeping: Mark NMI safe time accessors as notrace

2022-04-28T22:07:53Z

Mark the CLOCK_MONOTONIC fast time accessors as notrace. These functions are used in tracing to retrieve timestamps, so they should not recurse. Fixes: 4498e7467e9e ("time: Parametrize all tk_fast_mono users") Fixes: f09cb9a1808e ("time: Introduce tk_fast_raw") Reported-by: Steven Rostedt Signed-off-by: Kurt Kanzenbach Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220426175338.3807ca4f@gandalf.local.home/ Link: https://lore.kernel.org/r/20220428062432.61063-1-kurt@linutronix.de

tick/sched: Fix non-kernel-doc comment

2022-04-10T10:23:34Z

Fixes the following W=1 kernel build warning: kernel/time/tick-sched.c:1563: warning: This comment starts with '/**', but isn't a kernel-doc comment. Reported-by: Abaci Robot Signed-off-by: Jiapeng Chong Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220214084739.63228-1-jiapeng.chong@linux.alibaba.com

tick/nohz: Use WARN_ON_ONCE() to prevent console saturation

2022-04-10T10:23:34Z

While running some testing on code that happened to allow the variable tick_nohz_full_running to get set but with no "possible" NOHZ cores to back up that setting, this warning triggered: if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) WARN_ON(tick_nohz_full_running); The console was overwhemled with an endless stream of one WARN per tick per core and there was no way to even see what was going on w/o using a serial console to capture it and then trace it back to this. Change it to WARN_ON_ONCE(). Fixes: 08ae95f4fd3b ("nohz_full: Allow the boot CPU to be nohz_full") Signed-off-by: Paul Gortmaker Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211206145950.10927-3-paul.gortmaker@windriver.com

timers: Fix warning condition in __run_timers()

2022-04-09T20:17:47Z

When the timer base is empty, base::next_expiry is set to base::clk + NEXT_TIMER_MAX_DELTA and base::next_expiry_recalc is false. When no timer is queued until jiffies reaches base::next_expiry value, the warning for not finding any expired timer and base::next_expiry_recalc is false in __run_timers() triggers. To prevent triggering the warning in this valid scenario base::timers_pending needs to be added to the warning condition. Fixes: 31cd0e119d50 ("timers: Recalculate next timer interrupt only when necessary") Reported-by: Johannes Berg Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20220405191732.7438-3-anna-maria@linutronix.de

Merge tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-03-29T00:29:53Z

Pull ptrace cleanups from Eric Biederman: "This set of changes removes tracehook.h, moves modification of all of the ptrace fields inside of siglock to remove races, adds a missing permission check to ptrace.c The removal of tracehook.h is quite significant as it has been a major source of confusion in recent years. Much of that confusion was around task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled making the semantics clearer). For people who don't know tracehook.h is a vestiage of an attempt to implement uprobes like functionality that was never fully merged, and was later superseeded by uprobes when uprobes was merged. For many years now we have been removing what tracehook functionaly a little bit at a time. To the point where anything left in tracehook.h was some weird strange thing that was difficult to understand" * tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: ptrace: Remove duplicated include in ptrace.c ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE ptrace: Return the signal to continue with from ptrace_stop ptrace: Move setting/clearing ptrace_message into ptrace_stop tracehook: Remove tracehook.h resume_user_mode: Move to resume_user_mode.h resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume signal: Move set_notify_signal and clear_notify_signal into sched/signal.h task_work: Decouple TIF_NOTIFY_SIGNAL and task_work task_work: Call tracehook_notify_signal from get_signal on all architectures task_work: Introduce task_work_pending task_work: Remove unnecessary include from posix_timers.h ptrace: Remove tracehook_signal_handler ptrace: Remove arch_syscall_{enter,exit}_tracehook ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h ptrace/arm: Rename tracehook_report_syscall report_syscall ptrace: Move ptrace_report_syscall into ptrace.h

Merge tag 'prlimit-tasklist_lock-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-03-24T17:16:00Z

Pull tasklist_lock optimizations from Eric Biederman: "prlimit and getpriority tasklist_lock optimizations The tasklist_lock popped up as a scalability bottleneck on some testing workloads. The readlocks in do_prlimit and set/getpriority are not necessary in all cases. Based on a cycles profile, it looked like ~87% of the time was spent in the kernel, ~42% of which was just trying to get *some* spinlock (queued_spin_lock_slowpath, not necessarily the tasklist_lock). The big offenders (with rough percentages in cycles of the overall trace): - do_wait 11% - setpriority 8% (done previously in commit 7f8ca0edfe07) - kill 8% - do_exit 5% - clone 3% - prlimit64 2% (this patchset) - getrlimit 1% (this patchset) I can't easily test this patchset on the original workload for various reasons. Instead, I used the microbenchmark below to at least verify there was some improvement. This patchset had a 28% speedup (12% from baseline to set/getprio, then another 14% for prlimit). This series used to do the setpriority case, but an almost identical change was merged as commit 7f8ca0edfe07 ("kernel/sys.c: only take tasklist_lock for get/setpriority(PRIO_PGRP)") so that has been dropped from here. One interesting thing is that my libc's getrlimit() was calling prlimit64, so hoisting the read_lock(tasklist_lock) into sys_prlimit64 had no effect - it essentially optimized the older syscalls only. I didn't do that in this patchset, but figured I'd mention it since it was an option from the previous patch's discussion" micobenchmark.c: --------------- int main(int argc, char **argv) { pid_t child; struct rlimit rlim[1]; fork(); fork(); fork(); fork(); fork(); fork(); for (int i = 0; i < 5000; i++) { child = fork(); if (child < 0) exit(1); if (child > 0) { usleep(1000); kill(child, SIGTERM); waitpid(child, NULL, 0); } else { for (;;) { setpriority(PRIO_PROCESS, 0, getpriority(PRIO_PROCESS, 0)); getrlimit(RLIMIT_CPU, rlim); } } } return 0; } Link: https://lore.kernel.org/lkml/20211213220401.1039578-1-brho@google.com/ [v1] Link: https://lore.kernel.org/lkml/20220105212828.197013-1-brho@google.com/ [v2] Link: https://lore.kernel.org/lkml/20220106172041.522167-1-brho@google.com/ [v3] * tag 'prlimit-tasklist_lock-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: prlimit: do not grab the tasklist_lock prlimit: make do_prlimit() static

task_work: Remove unnecessary include from posix_timers.h

2022-03-10T19:38:01Z

Break a header file circular dependency by removing the unnecessary include of task_work.h from posix_timers.h. sched.h -> posix-timers.h posix-timers.h -> task_work.h task_work.h -> sched.h Add missing includes of task_work.h to: arch/x86/mm/tlb.c kernel/time/posix-cpu-timers.c Reviewed-by: Kees Cook Link: https://lkml.kernel.org/r/20220309162454.123006-6-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman"