user/sven/linux.git/include/linux/sched.h, branch v6.17.3

sched/deadline: Fix dl_server behaviour

2025-09-25T07:51:50Z

John reported undesirable behaviour with the dl_server since commit: cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling"). When starving fair tasks on purpose (starting spinning FIFO tasks), his fair workload, which often goes (briefly) idle, would delay fair invocations for a second, running one invocation per second was both unexpected and terribly slow. The reason this happens is that when dl_se->server_pick_task() returns NULL, indicating no runnable tasks, it would yield, pushing any later jobs out a whole period (1 second). Instead simply stop the server. This should restore behaviour in that a later wakeup (which restarts the server) will be able to continue running (subject to the CBS wakeup rules). Notably, this does not re-introduce the behaviour cccb45d7c4295 set out to solve, any start/stop cycle is naturally throttled by the timer period (no active cancel). Fixes: cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling") Reported-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Peter Zijlstra (Intel) Tested-by: John Stultz

sched/deadline: Fix dl_server getting stuck

2025-09-25T07:51:50Z

John found it was easy to hit lockup warnings when running locktorture on a 2 CPU VM, which he bisected down to: commit cccb45d7c429 ("sched/deadline: Less agressive dl_server handling"). While debugging it seems there is a chance where we end up with the dl_server dequeued, with dl_se->dl_server_active. This causes dl_server_start() to return without enqueueing the dl_server, thus it fails to run when RT tasks starve the cpu. When this happens, dl_server_timer() catches the '!dl_se->server_has_tasks(dl_se)' case, which then calls replenish_dl_entity() and dl_server_stopped() and finally return HRTIMER_NO_RESTART. This ends in no new timer and also no enqueue, leaving the dl_server 'dead', allowing starvation. What should have happened is for the bandwidth timer to start the zero-laxity timer, which in turn would enqueue the dl_server and cause dl_se->server_pick_task() to be called -- which will stop the dl_server if no fair tasks are observed for a whole period. IOW, it is totally irrelevant if there are fair tasks at the moment of bandwidth refresh. This removes all dl_se->server_has_tasks() users, so remove the whole thing. Fixes: cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling") Reported-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Peter Zijlstra (Intel) Tested-by: John Stultz

Merge tag 'locking_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2025-08-17T12:57:47Z

Pull locking fixes from Borislav Petkov: - Make sure sanity checks down in the mutex lock path happen on the correct type of task so that they don't trigger falsely - Use the write unsafe user access pairs when writing a futex value to prevent an error on PowerPC which does user read and write accesses differently * tag 'locking_urgent_for_v6.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: locking: Fix __clear_task_blocked_on() warning from __ww_mutex_wound() path futex: Use user_write_access_begin/_end() in futex_put_value()

locking: Fix __clear_task_blocked_on() warning from __ww_mutex_wound() path

2025-08-13T08:34:54Z

The __clear_task_blocked_on() helper added a number of sanity checks ensuring we hold the mutex wait lock and that the task we are clearing blocked_on pointer (if set) matches the mutex. However, there is an edge case in the _ww_mutex_wound() logic where we need to clear the blocked_on pointer for the task that owns the mutex, not the task that is waiting on the mutex. For this case the sanity checks aren't valid, so handle this by allowing a NULL lock to skip the additional checks. K Prateek Nayak and Maarten Lankhorst also pointed out that in this case where we don't hold the owner's mutex wait_lock, we need to be a bit more careful using READ_ONCE/WRITE_ONCE in both the __clear_task_blocked_on() and __set_task_blocked_on() implementations to avoid accidentally tripping WARN_ONs if two instances race. So do that here as well. This issue was easier to miss, I realized, as the test-ww_mutex driver only exercises the wait-die class of ww_mutexes. I've sent a patch[1] to address this so the logic will be easier to test. [1]: https://lore.kernel.org/lkml/20250801023358.562525-2-jstultz@google.com/ Fixes: a4f0b6fef4b0 ("locking/mutex: Add p->blocked_on wrappers for correctness checks") Closes: https://lore.kernel.org/lkml/68894443.a00a0220.26d0e1.0015.GAE@google.com/ Reported-by: syzbot+602c4720aed62576cd79@syzkaller.appspotmail.com Reported-by: Maarten Lankhorst Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: K Prateek Nayak Acked-by: Maarten Lankhorst Tested-by: K Prateek Nayak Link: https://lore.kernel.org/r/20250805001026.2247040-1-jstultz@google.com

Merge tag 'trace-deferred-unwind-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2025-08-01T16:46:24Z

Pull initial deferred unwind infrastructure from Steven Rostedt: "This is the core infrastructure for the deferred unwinder that is required for sframes[1]. Several other patch series are based on this work although those patch series are not dependent on each other. In order to simplify the development, having this core series upstream will allow the other series to be worked on in parallel. The other series are: - The two patches to implement x86 support [2] [3] - The s390 work [4] - The perf work [5] - The ftrace work [6] - The sframe work [7] And more is on the way. The core infrastructure adds the following in kernel APIs: - int unwind_user_faultable(struct unwind_stacktrace *trace); Performs a user space stack trace that may fault user pages in. - int unwind_deferred_init(struct unwind_work *work, unwind_callback_t func); Allows a tracer to register with the unwind deferred infrastructure. - int unwind_deferred_request(struct unwind_work *work, u64 *cookie); Used when a tracer request a deferred trace. Can be called from interrupt or NMI context. - void unwind_deferred_cancel(struct unwind_work *work); Called by a tracer to unregister from the deferred unwind infrastructure. - void unwind_deferred_task_exit(struct task_struct *task); Called by task exit code to flush any pending unwind requests. - void unwind_task_init(struct task_struct *task); Called by do_fork() to initialize the task struct for the deferred unwinder. - void unwind_task_free(struct task_struct *task); Called by do_exit() to free up any resources used by the deferred unwinder. None of the above is actually compiled unless an architecture enables it, which none currently do" Link: https://sourceware.org/binutils/wiki/sframe [1] Link: https://lore.kernel.org/linux-trace-kernel/20250717004958.260781923@kernel.org/ [2] Link: https://lore.kernel.org/linux-trace-kernel/20250717004958.432327787@kernel.org/ [3] Link: https://lore.kernel.org/linux-trace-kernel/20250710163522.3195293-1-jremus@linux.ibm.com/ [4] Link: https://lore.kernel.org/linux-trace-kernel/20250718164119.089692174@kernel.org/ [5] Link: https://lore.kernel.org/linux-trace-kernel/20250424192612.505622711@goodmis.org/ [6] Link: https://lore.kernel.org/linux-trace-kernel/20250717012848.927473176@kernel.org/ [7] * tag 'trace-deferred-unwind-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: unwind: Finish up unwind when a task exits unwind deferred: Use SRCU unwind_deferred_task_work() unwind: Add USED bit to only have one conditional on way back to user space unwind deferred: Add unwind_completed mask to stop spurious callbacks unwind deferred: Use bitmask to determine which callbacks to call unwind_user/deferred: Make unwind deferral requests NMI-safe unwind_user/deferred: Add deferred unwinding interface unwind_user/deferred: Add unwind cache unwind_user/deferred: Add unwind_user_faultable() unwind_user: Add user space unwinding API with frame pointer support

Merge tag 'trace-rv-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2025-07-30T23:23:12Z

Pull runtime verification updates from Steven Rostedt: - Added Linear temporal logic monitors for RT application Real-time applications may have design flaws causing them to have unexpected latency. For example, the applications may raise page faults, or may be blocked trying to take a mutex without priority inheritance. However, while attempting to implement DA monitors for these real-time rules, deterministic automaton is found to be inappropriate as the specification language. The automaton is complicated, hard to understand, and error-prone. For these cases, linear temporal logic is found to be more suitable. The LTL is more concise and intuitive. - Make printk_deferred() public The new monitors needed access to printk_deferred(). Make them visible for the entire kernel. - Add a vpanic() to allow for va_list to be passed to panic. - Add rtapp container monitor. A collection of monitors that check for common problems with real-time applications that cause unexpected latency. - Add page fault tracepoints to risc-v These tracepoints are necessary to for the RV monitor to run on risc-v. - Fix the behaviour of the rv tool with -s and idle tasks. - Allow the rv tool to gracefully terminate with SIGTERM - Adjusts dot2c not to create lines over 100 columns - Properly order nested monitors in the RV Kconfig file - Return the registration error in all DA monitor instead of 0 - Update and add new sched collection monitors Replace tss and sncid monitors with more complete sts: Not only prove that switches occur in scheduling context and scheduling needs interrupt disabled but also that each call to the scheduler disables interrupts to (optionally) switch. New monitor: nrp Preemption requires need resched which is cleared by any switch (includes a non optimal workaround for /nested/ preemptions) New monitor: sssw suspension requires setting the task to sleepable and, after the switch occurs, the task requires a wakeup to come back to runnable New monitor: opid waking and need-resched operations occur with interrupts and preemption disabled or in IRQ without explicitly disabling preemption" * tag 'trace-rv-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (48 commits) rv: Add opid per-cpu monitor rv: Add nrp and sssw per-task monitors rv: Replace tss and sncid monitors with more complete sts sched: Adapt sched tracepoints for RV task model rv: Retry when da monitor detects race conditions rv: Adjust monitor dependencies rv: Use strings in da monitors tracepoints rv: Remove trailing whitespace from tracepoint string rv: Add da_handle_start_run_event_ to per-task monitors rv: Fix wrong type cast in reactors_show() and monitor_reactor_show() rv: Fix wrong type cast in monitors_show() rv: Remove struct rv_monitor::reacting rv: Remove rv_reactor's reference counter rv: Merge struct rv_reactor_def into struct rv_reactor rv: Merge struct rv_monitor_def into struct rv_monitor rv: Remove unused field in struct rv_monitor_def rv: Return init error when registering monitors verification/rvgen: Organise Kconfig entries for nested monitors tools/dot2c: Fix generated files going over 100 column limit tools/rv: Stop gracefully also on SIGTERM ...

Merge tag 'sched-core-2025-07-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2025-07-30T00:42:52Z

Pull scheduler updates from Ingo Molnar: "Core scheduler changes: - Better tracking of maximum lag of tasks in presence of different slices duration, for better handling of lag in the fair scheduler (Vincent Guittot) - Clean up and standardize #if/#else/#endif markers throughout the entire scheduler code base (Ingo Molnar) - Make SMP unconditional: build the SMP scheduler's data structures and logic on UP kernel too, even though they are not used, to simplify the scheduler and remove around 200 #ifdef/[#else]/#endif blocks from the scheduler (Ingo Molnar) - Reorganize cgroup bandwidth control interface handling for better interfacing with sched_ext (Tejun Heo) Balancing: - Bump sd->max_newidle_lb_cost when newidle balance fails (Chris Mason) - Remove sched_domain_topology_level::flags to simplify the code (Prateek Nayak) - Simplify and clean up build_sched_topology() (Li Chen) - Optimize build_sched_topology() on large machines (Li Chen) Real-time scheduling: - Add initial version of proxy execution: a mechanism for mutex-owning tasks to inherit the scheduling context of higher priority waiters. Currently limited to a single runqueue and conditional on CONFIG_EXPERT, and other limitations (John Stultz, Peter Zijlstra, Valentin Schneider) - Deadline scheduler (Juri Lelli): - Fix dl_servers initialization order (Juri Lelli) - Fix DL scheduler's root domain reinitialization logic (Juri Lelli) - Fix accounting bugs after global limits change (Juri Lelli) - Fix scalability regression by implementing less agressive dl_server handling (Peter Zijlstra) PSI: - Improve scalability by optimizing psi_group_change() cpu_clock() usage (Peter Zijlstra) Rust changes: - Make Task, CondVar and PollCondVar methods inline to avoid unnecessary function calls (Kunwu Chan, Panagiotis Foliadis) - Add might_sleep() support for Rust code: Rust's "#[track_caller]" mechanism is used so that Rust's might_sleep() doesn't need to be defined as a macro (Fujita Tomonori) - Introduce file_from_location() (Boqun Feng) Debugging & instrumentation: - Make clangd usable with scheduler source code files again (Peter Zijlstra) - tools: Add root_domains_dump.py which dumps root domains info (Juri Lelli) - tools: Add dl_bw_dump.py for printing bandwidth accounting info (Juri Lelli) Misc cleanups & fixes: - Remove play_idle() (Feng Lee) - Fix check_preemption_disabled() (Sebastian Andrzej Siewior) - Do not call __put_task_struct() on RT if pi_blocked_on is set (Luis Claudio R. Goncalves) - Correct the comment in place_entity() (wang wei)" * tag 'sched-core-2025-07-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (84 commits) sched/idle: Remove play_idle() sched: Do not call __put_task_struct() on rt if pi_blocked_on is set sched: Start blocked_on chain processing in find_proxy_task() sched: Fix proxy/current (push,pull)ability sched: Add an initial sketch of the find_proxy_task() function sched: Fix runtime accounting w/ split exec & sched contexts sched: Move update_curr_task logic into update_curr_se locking/mutex: Add p->blocked_on wrappers for correctness checks locking/mutex: Rework task_struct::blocked_on sched: Add CONFIG_SCHED_PROXY_EXEC & boot argument to enable/disable sched/topology: Remove sched_domain_topology_level::flags x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled x86/smpboot: moves x86_topology to static initialize and truncate x86/smpboot: remove redundant CONFIG_SCHED_SMT smpboot: introduce SDTL_INIT() helper to tidy sched topology setup tools/sched: Add dl_bw_dump.py for printing bandwidth accounting info tools/sched: Add root_domains_dump.py which dumps root domains info sched/deadline: Fix accounting after global limits change sched/deadline: Reset extra_bw to max_bw when clearing root domains sched/deadline: Initialize dl_servers after SMP ...

unwind_user/deferred: Add unwind_user_faultable()

2025-07-29T18:46:07Z

Add a new API to retrieve a user space callstack called unwind_user_faultable(). The difference between this user space stack tracer from the current user space stack tracer is that this must be called from faultable context as it may use routines to access user space data that needs to be faulted in. It can be safely called from entering or exiting a system call as the code can still be faulted in there. This code is based on work by Josh Poimboeuf's deferred unwinding code: Link: https://lore.kernel.org/all/6052e8487746603bdb29b65f4033e739092d9925.1737511963.git.jpoimboe@kernel.org/ Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Jiri Olsa Cc: Arnaldo Carvalho de Melo Cc: Namhyung Kim Cc: Thomas Gleixner Cc: Andrii Nakryiko Cc: Indu Bhagat Cc: "Jose E. Marchesi" Cc: Beau Belgrave Cc: Linus Torvalds Cc: Andrew Morton Cc: Jens Axboe Cc: Florian Weimer Cc: Sam James Link: https://lore.kernel.org/20250729182405.147896868@kernel.org Reviewed-by: Jens Remus Signed-off-by: Steven Rostedt (Google)

Merge tag 'hardening-v6.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

2025-07-29T00:16:12Z

Pull hardening updates from Kees Cook: - Introduce and start using TRAILING_OVERLAP() helper for fixing embedded flex array instances (Gustavo A. R. Silva) - mux: Convert mux_control_ops to a flex array member in mux_chip (Thorsten Blum) - string: Group str_has_prefix() and strstarts() (Andy Shevchenko) - Remove KCOV instrumentation from __init and __head (Ritesh Harjani, Kees Cook) - Refactor and rename stackleak feature to support Clang - Add KUnit test for seq_buf API - Fix KUnit fortify test under LTO * tag 'hardening-v6.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (22 commits) sched/task_stack: Add missing const qualifier to end_of_stack() kstack_erase: Support Clang stack depth tracking kstack_erase: Add -mgeneral-regs-only to silence Clang warnings init.h: Disable sanitizer coverage for __init and __head kstack_erase: Disable kstack_erase for all of arm compressed boot code x86: Handle KCOV __init vs inline mismatches arm64: Handle KCOV __init vs inline mismatches s390: Handle KCOV __init vs inline mismatches arm: Handle KCOV __init vs inline mismatches mips: Handle KCOV __init vs inline mismatch powerpc/mm/book3s64: Move kfence and debug_pagealloc related calls to __init section configs/hardening: Enable CONFIG_INIT_ON_FREE_DEFAULT_ON configs/hardening: Enable CONFIG_KSTACK_ERASE stackleak: Split KSTACK_ERASE_CFLAGS from GCC_PLUGINS_CFLAGS stackleak: Rename stackleak_track_stack to __sanitizer_cov_stack_depth stackleak: Rename STACKLEAK to KSTACK_ERASE seq_buf: Introduce KUnit tests string: Group str_has_prefix() and strstarts() kunit/fortify: Add back "volatile" for sizeof() constants acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings ...

sched: Adapt sched tracepoints for RV task model

2025-07-28T20:47:34Z

Add the following tracepoint: * sched_set_need_resched(tsk, cpu, tif) Called when a task is set the need resched [lazy] flag Remove the unused ip parameter from sched_entry and sched_exit and alter sched_entry to have a value of preempt consistent with the one used in sched_switch. Also adapt all monitors using sched_{entry,exit} to avoid breaking build. These tracepoints are useful to describe the Linux task model and are adapted from the patches by Daniel Bristot de Oliveira (https://bristot.me/linux-task-model/). Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Masami Hiramatsu Cc: Nam Cao Cc: Tomas Glozar Cc: Juri Lelli Cc: Clark Williams Cc: John Kacur Link: https://lore.kernel.org/20250728135022.255578-7-gmonaco@redhat.com Signed-off-by: Gabriele Monaco Signed-off-by: Steven Rostedt (Google)