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Pull sched_ext fixes from Tejun Heo:
"A little bit invasive for rc6 but they're important fixes, pass tests
fine and won't break anything outside sched_ext:
- scx_bpf_cpuperf_set() calls internal functions that require the rq
to be locked. It assumed that the BPF caller has rq locked but
that's not always true. Fix it by tracking whether rq is currently
held by the CPU and grabbing it if necessary
- bpf_iter_scx_dsq_new() was leaving the DSQ iterator in an
uninitialized state after an error. However, next() and destroy()
can be called on an iterator which failed initialization and thus
they always need to be initialized even after an init error. Fix by
always initializing the iterator
- Remove duplicate BTF_ID_FLAGS() entries"
* tag 'sched_ext-for-6.15-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext: bpf_iter_scx_dsq_new() should always initialize iterator
sched_ext: Fix rq lock state in hotplug ops
sched_ext: Remove duplicate BTF_ID_FLAGS definitions
sched_ext: Fix missing rq lock in scx_bpf_cpuperf_set()
sched_ext: Track currently locked rq
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BPF programs may call next() and destroy() on BPF iterators even after new()
returns an error value (e.g. bpf_for_each() macro ignores error returns from
new()). bpf_iter_scx_dsq_new() could leave the iterator in an uninitialized
state after an error return causing bpf_iter_scx_dsq_next() to dereference
garbage data. Make bpf_iter_scx_dsq_new() always clear $kit->dsq so that
next() and destroy() become noops.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 650ba21b131e ("sched_ext: Implement DSQ iterator")
Cc: stable@vger.kernel.org # v6.12+
Acked-by: Andrea Righi <arighi@nvidia.com>
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The ops.cpu_online() and ops.cpu_offline() callbacks incorrectly assume
that the rq involved in the operation is locked, which is not the case
during hotplug, triggering the following warning:
WARNING: CPU: 1 PID: 20 at kernel/sched/sched.h:1504 handle_hotplug+0x280/0x340
Fix by not tracking the target rq as locked in the context of
ops.cpu_online() and ops.cpu_offline().
Fixes: 18853ba782bef ("sched_ext: Track currently locked rq")
Reported-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Tested-by: Changwoo Min <changwoo@igalia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull scheduler fix from Ingo Molnar:
"Fix sporadic crashes in dequeue_entities() due to ... bad math.
[ Arguably if pick_eevdf()/pick_next_entity() was less trusting of
complex math being correct it could have de-escalated a crash into
a warning, but that's for a different patch ]"
* tag 'sched-urgent-2025-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/eevdf: Fix se->slice being set to U64_MAX and resulting crash
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There is a code path in dequeue_entities() that can set the slice of a
sched_entity to U64_MAX, which sometimes results in a crash.
The offending case is when dequeue_entities() is called to dequeue a
delayed group entity, and then the entity's parent's dequeue is delayed.
In that case:
1. In the if (entity_is_task(se)) else block at the beginning of
dequeue_entities(), slice is set to
cfs_rq_min_slice(group_cfs_rq(se)). If the entity was delayed, then
it has no queued tasks, so cfs_rq_min_slice() returns U64_MAX.
2. The first for_each_sched_entity() loop dequeues the entity.
3. If the entity was its parent's only child, then the next iteration
tries to dequeue the parent.
4. If the parent's dequeue needs to be delayed, then it breaks from the
first for_each_sched_entity() loop _without updating slice_.
5. The second for_each_sched_entity() loop sets the parent's ->slice to
the saved slice, which is still U64_MAX.
This throws off subsequent calculations with potentially catastrophic
results. A manifestation we saw in production was:
6. In update_entity_lag(), se->slice is used to calculate limit, which
ends up as a huge negative number.
7. limit is used in se->vlag = clamp(vlag, -limit, limit). Because limit
is negative, vlag > limit, so se->vlag is set to the same huge
negative number.
8. In place_entity(), se->vlag is scaled, which overflows and results in
another huge (positive or negative) number.
9. The adjusted lag is subtracted from se->vruntime, which increases or
decreases se->vruntime by a huge number.
10. pick_eevdf() calls entity_eligible()/vruntime_eligible(), which
incorrectly returns false because the vruntime is so far from the
other vruntimes on the queue, causing the
(vruntime - cfs_rq->min_vruntime) * load calulation to overflow.
11. Nothing appears to be eligible, so pick_eevdf() returns NULL.
12. pick_next_entity() tries to dereference the return value of
pick_eevdf() and crashes.
Dumping the cfs_rq states from the core dumps with drgn showed tell-tale
huge vruntime ranges and bogus vlag values, and I also traced se->slice
being set to U64_MAX on live systems (which was usually "benign" since
the rest of the runqueue needed to be in a particular state to crash).
Fix it in dequeue_entities() by always setting slice from the first
non-empty cfs_rq.
Fixes: aef6987d8954 ("sched/eevdf: Propagate min_slice up the cgroup hierarchy")
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/f0c2d1072be229e1bdddc73c0703919a8b00c652.1745570998.git.osandov@fb.com
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Some kfuncs specific to the idle CPU selection policy are registered in
both the scx_kfunc_ids_any and scx_kfunc_ids_idle blocks, even though
they should only be defined in the latter.
Remove the duplicates from scx_kfunc_ids_any.
Fixes: 337d1b354a297 ("sched_ext: Move built-in idle CPU selection policy to a separate file")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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scx_bpf_cpuperf_set() can be used to set a performance target level on
any CPU. However, it doesn't correctly acquire the corresponding rq
lock, which may lead to unsafe behavior and trigger the following
warning, due to the lockdep_assert_rq_held() check:
[ 51.713737] WARNING: CPU: 3 PID: 3899 at kernel/sched/sched.h:1512 scx_bpf_cpuperf_set+0x1a0/0x1e0
...
[ 51.713836] Call trace:
[ 51.713837] scx_bpf_cpuperf_set+0x1a0/0x1e0 (P)
[ 51.713839] bpf_prog_62d35beb9301601f_bpfland_init+0x168/0x440
[ 51.713841] bpf__sched_ext_ops_init+0x54/0x8c
[ 51.713843] scx_ops_enable.constprop.0+0x2c0/0x10f0
[ 51.713845] bpf_scx_reg+0x18/0x30
[ 51.713847] bpf_struct_ops_link_create+0x154/0x1b0
[ 51.713849] __sys_bpf+0x1934/0x22a0
Fix by properly acquiring the rq lock when possible or raising an error
if we try to operate on a CPU that is not the one currently locked.
Fixes: d86adb4fc0655 ("sched_ext: Add cpuperf support")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Acked-by: Changwoo Min <changwoo@igalia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Some kfuncs provided by sched_ext may need to operate on a struct rq,
but they can be invoked from various contexts, specifically, different
scx callbacks.
While some of these callbacks are invoked with a particular rq already
locked, others are not. This makes it impossible for a kfunc to reliably
determine whether it's safe to access a given rq, triggering potential
bugs or unsafe behaviors, see for example [1].
To address this, track the currently locked rq whenever a sched_ext
callback is invoked via SCX_CALL_OP*().
This allows kfuncs that need to operate on an arbitrary rq to retrieve
the currently locked one and apply the appropriate action as needed.
[1] https://lore.kernel.org/lkml/20250325140021.73570-1-arighi@nvidia.com/
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Acked-by: Changwoo Min <changwoo@igalia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull sched_ext fixes from Tejun Heo:
- Use kvzalloc() so that large exit_dump buffer allocations don't fail
easily
- Remove cpu.weight / cpu.idle unimplemented warnings which are more
annoying than helpful.
This makes SCX_OPS_HAS_CGROUP_WEIGHT unnecessary. Mark it for
deprecation
* tag 'sched_ext-for-6.15-rc3-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext: Mark SCX_OPS_HAS_CGROUP_WEIGHT for deprecation
sched_ext: Remove cpu.weight / cpu.idle unimplemented warnings
sched_ext: Use kvzalloc for large exit_dump allocation
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Notice that ignore_dl_rate_limit() need not piggy back on the
limits_changed handling to achieve its goal (which is to enforce a
frequency update before its due time).
Namely, if sugov_should_update_freq() is updated to check
sg_policy->need_freq_update and return 'true' if it is set when
sg_policy->limits_changed is not set, ignore_dl_rate_limit() may
set the former directly instead of setting the latter, so it can
avoid hitting the memory barrier in sugov_should_update_freq().
Update the code accordingly.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/10666429.nUPlyArG6x@rjwysocki.net
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The handling of the limits_changed flag in struct sugov_policy needs to
be explicitly synchronized to ensure that cpufreq policy limits updates
will not be missed in some cases.
Without that synchronization it is theoretically possible that
the limits_changed update in sugov_should_update_freq() will be
reordered with respect to the reads of the policy limits in
cpufreq_driver_resolve_freq() and in that case, if the limits_changed
update in sugov_limits() clobbers the one in sugov_should_update_freq(),
the new policy limits may not take effect for a long time.
Likewise, the limits_changed update in sugov_limits() may theoretically
get reordered with respect to the updates of the policy limits in
cpufreq_set_policy() and if sugov_should_update_freq() runs between
them, the policy limits change may be missed.
To ensure that the above situations will not take place, add memory
barriers preventing the reordering in question from taking place and
add READ_ONCE() and WRITE_ONCE() annotations around all of the
limits_changed flag updates to prevent the compiler from messing up
with that code.
Fixes: 600f5badb78c ("cpufreq: schedutil: Don't skip freq update when limits change")
Cc: 5.3+ <stable@vger.kernel.org> # 5.3+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/3376719.44csPzL39Z@rjwysocki.net
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Commit 8e461a1cb43d ("cpufreq: schedutil: Fix superfluous updates caused
by need_freq_update") modified sugov_should_update_freq() to set the
need_freq_update flag only for drivers with CPUFREQ_NEED_UPDATE_LIMITS
set, but that flag generally needs to be set when the policy limits
change because the driver callback may need to be invoked for the new
limits to take effect.
However, if the return value of cpufreq_driver_resolve_freq() after
applying the new limits is still equal to the previously selected
frequency, the driver callback needs to be invoked only in the case
when CPUFREQ_NEED_UPDATE_LIMITS is set (which means that the driver
specifically wants its callback to be invoked every time the policy
limits change).
Update the code accordingly to avoid missing policy limits changes for
drivers without CPUFREQ_NEED_UPDATE_LIMITS.
Fixes: 8e461a1cb43d ("cpufreq: schedutil: Fix superfluous updates caused by need_freq_update")
Closes: https://lore.kernel.org/lkml/Z_Tlc6Qs-tYpxWYb@linaro.org/
Reported-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/3010358.e9J7NaK4W3@rjwysocki.net
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SCX_OPS_HAS_CGROUP_WEIGHT was only used to suppress the missing cgroup
weight support warnings. Now that the warnings are removed, the flag doesn't
do anything. Mark it for deprecation and remove its usage from scx_flatcg.
v2: Actually include the scx_flatcg update.
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-and-reviewed-by: Andrea Righi <arighi@nvidia.com>
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sched_ext generates warnings when cpu.weight / cpu.idle are set to
non-default values if the BPF scheduler doesn't implement weight support.
These warnings don't provide much value while adding constant annoyance. A
BPF scheduler may not implement any particular behavior and there's nothing
particularly special about missing cgroup weight support. Drop the warnings.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Replace kzalloc with kvzalloc for the exit_dump buffer allocation, which
can require large contiguous memory depending on the implementation.
This change prevents allocation failures by allowing the system to fall
back to vmalloc when contiguous memory allocation fails.
Since this buffer is only used for debugging purposes, physical memory
contiguity is not required, making vmalloc a suitable alternative.
Cc: stable@vger.kernel.org
Fixes: 07814a9439a3b0 ("sched_ext: Print debug dump after an error exit")
Suggested-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull scheduler fixes from Ingo Molnar:
- Fix a nonsensical Kconfig combination
- Remove an unnecessary rseq-notification
* tag 'sched-urgent-2025-04-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rseq: Eliminate useless task_work on execve
sched/isolation: Make CONFIG_CPU_ISOLATION depend on CONFIG_SMP
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timer_delete[_sync]() replaces del_timer[_sync](). Convert the whole tree
over and remove the historical wrapper inlines.
Conversion was done with coccinelle plus manual fixups where necessary.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Pull sched_ext fixes from Tejun Heo:
- Calling scx_bpf_create_dsq() with the same ID would succeed creating
duplicate DSQs. Fix it to return -EEXIST.
- scx_select_cpu_dfl() fixes and cleanups.
- Synchronize tool/sched_ext with external scheduler repo. While this
isn't a fix. There's no risk to the kernel and it's better if they
stay synced closer.
* tag 'sched_ext-for-6.15-rc0-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
tools/sched_ext: Sync with scx repo
sched_ext: initialize built-in idle state before ops.init()
sched_ext: create_dsq: Return -EEXIST on duplicate request
sched_ext: Remove a meaningless conditional goto in scx_select_cpu_dfl()
sched_ext: idle: Fix return code of scx_select_cpu_dfl()
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Eliminate a useless task_work on execve by moving the call to
rseq_set_notify_resume() from sched_mm_cid_after_execve() to the error
path of bprm_execve().
The call to rseq_set_notify_resume() from sched_mm_cid_after_execve() is
pointless in the success case, because rseq_execve() will clear the rseq
pointer before returning to userspace.
sched_mm_cid_after_execve() is called from both the success and error
paths of bprm_execve(). The call to rseq_set_notify_resume() is needed
on error because the mm_cid may have changed.
Also move the rseq_execve() to right after sched_mm_cid_after_execve()
in bprm_execve().
[ mingo: Merged to a recent upstream kernel, extended the changelog. ]
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250327132945.1558783-1-mathieu.desnoyers@efficios.com
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Pull latency tracing updates from Steven Rostedt:
- Add some trace events to osnoise and timerlat sample generation
This adds more information to the osnoise and timerlat tracers as
well as allows BPF programs to be attached to these locations to
extract even more data.
- Fix to DECLARE_TRACE_CONDITION() macro
It wasn't used but now will be and it happened to be broken causing
the build to fail.
- Add scheduler specification monitors to runtime verifier (RV)
This is a continuation of Daniel Bristot's work.
RV allows monitors to run and react concurrently. Running the
cumulative model is equivalent to running single components using the
same reactors, with the advantage that it's easier to point out which
specification failed in case of error.
This update introduces nested monitors to RV, in short, the sysfs
monitor folder will contain a monitor named sched, which is nothing
but an empty container for other monitors. Controlling the sched
monitor (enable, disable, set reactors) controls all nested monitors.
The following scheduling monitors are added:
- sco: scheduling context operations
Monitor to ensure sched_set_state happens only in thread context
- tss: task switch while scheduling
Monitor to ensure sched_switch happens only in scheduling context
- snroc: set non runnable on its own context
Monitor to ensure set_state happens only in the respective task's context
- scpd: schedule called with preemption disabled
Monitor to ensure schedule is called with preemption disabled
- snep: schedule does not enable preempt
Monitor to ensure schedule does not enable preempt
- sncid: schedule not called with interrupt disabled
Monitor to ensure schedule is not called with interrupt disabled
* tag 'trace-latency-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tools/rv: Allow rv list to filter for container
Documentation/rv: Add docs for the sched monitors
verification/dot2k: Add support for nested monitors
tools/rv: Add support for nested monitors
rv: Add scpd, snep and sncid per-cpu monitors
rv: Add snroc per-task monitor
rv: Add sco and tss per-cpu monitors
rv: Add option for nested monitors and include sched
sched: Add sched tracepoints for RV task model
rv: Add license identifiers to monitor files
tracing: Fix DECLARE_TRACE_CONDITION
trace/osnoise: Add trace events for samples
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A BPF scheduler may want to use the built-in idle cpumasks in ops.init()
before the scheduler is fully initialized, either directly or through a
BPF timer for example.
However, this would result in an error, since the idle state has not
been properly initialized yet.
This can be easily verified by modifying scx_simple to call
scx_bpf_get_idle_cpumask() in ops.init():
$ sudo scx_simple
DEBUG DUMP
===========================================================================
scx_simple[121] triggered exit kind 1024:
runtime error (built-in idle tracking is disabled)
...
Fix this by properly initializing the idle state before ops.init() is
called. With this change applied:
$ sudo scx_simple
local=2 global=0
local=19 global=11
local=23 global=11
...
Fixes: d73249f88743d ("sched_ext: idle: Make idle static keys private")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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create_dsq and therefore the scx_bpf_create_dsq kfunc currently silently
ignore duplicate entries. As a sched_ext scheduler is creating each DSQ
for a different purpose this is surprising behaviour.
Replace rhashtable_insert_fast which ignores duplicates with
rhashtable_lookup_insert_fast that reports duplicates (though doesn't
return their value). The rest of the code is structured correctly and
this now returns -EEXIST.
Tested by adding an extra scx_bpf_create_dsq to scx_simple. Previously
this was ignored, now init fails with a -17 code. Also ran scx_lavd
which continued to work well.
Signed-off-by: Jake Hillion <jake@hillion.co.uk>
Acked-by: Andrea Righi <arighi@nvidia.com>
Fixes: f0e1a0643a59 ("sched_ext: Implement BPF extensible scheduler class")
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Tejun Heo <tj@kernel.org>
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scx_select_cpu_dfl() has a meaningless conditional goto at the end. Remove
it. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrea Righi <arighi@nvidia.com>
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Return -EBUSY when using %SCX_PICK_IDLE_CORE with scx_select_cpu_dfl()
if a fully idle SMT core cannot be found, instead of falling back to
@prev_cpu, which is not a fully idle SMT core in this case.
Fixes: c414c2171cd9e ("sched_ext: idle: Honor idle flags in the built-in idle selection policy")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull timer cleanups from Thomas Gleixner:
"A treewide hrtimer timer cleanup
hrtimers are initialized with hrtimer_init() and a subsequent store to
the callback pointer. This turned out to be suboptimal for the
upcoming Rust integration and is obviously a silly implementation to
begin with.
This cleanup replaces the hrtimer_init(T); T->function = cb; sequence
with hrtimer_setup(T, cb);
The conversion was done with Coccinelle and a few manual fixups.
Once the conversion has completely landed in mainline, hrtimer_init()
will be removed and the hrtimer::function becomes a private member"
* tag 'timers-cleanups-2025-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (100 commits)
wifi: rt2x00: Switch to use hrtimer_update_function()
io_uring: Use helper function hrtimer_update_function()
serial: xilinx_uartps: Use helper function hrtimer_update_function()
ASoC: fsl: imx-pcm-fiq: Switch to use hrtimer_setup()
RDMA: Switch to use hrtimer_setup()
virtio: mem: Switch to use hrtimer_setup()
drm/vmwgfx: Switch to use hrtimer_setup()
drm/xe/oa: Switch to use hrtimer_setup()
drm/vkms: Switch to use hrtimer_setup()
drm/msm: Switch to use hrtimer_setup()
drm/i915/request: Switch to use hrtimer_setup()
drm/i915/uncore: Switch to use hrtimer_setup()
drm/i915/pmu: Switch to use hrtimer_setup()
drm/i915/perf: Switch to use hrtimer_setup()
drm/i915/gvt: Switch to use hrtimer_setup()
drm/i915/huc: Switch to use hrtimer_setup()
drm/amdgpu: Switch to use hrtimer_setup()
stm class: heartbeat: Switch to use hrtimer_setup()
i2c: Switch to use hrtimer_setup()
iio: Switch to use hrtimer_setup()
...
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Pull scheduler updates from Ingo Molnar:
"Core & fair scheduler changes:
- Cancel the slice protection of the idle entity (Zihan Zhou)
- Reduce the default slice to avoid tasks getting an extra tick
(Zihan Zhou)
- Force propagating min_slice of cfs_rq when {en,de}queue tasks
(Tianchen Ding)
- Refactor can_migrate_task() to elimate looping (I Hsin Cheng)
- Add unlikey branch hints to several system calls (Colin Ian King)
- Optimize current_clr_polling() on certain architectures (Yujun
Dong)
Deadline scheduler: (Juri Lelli)
- Remove redundant dl_clear_root_domain call
- Move dl_rebuild_rd_accounting to cpuset.h
Uclamp:
- Use the uclamp_is_used() helper instead of open-coding it (Xuewen
Yan)
- Optimize sched_uclamp_used static key enabling (Xuewen Yan)
Scheduler topology support: (Juri Lelli)
- Ignore special tasks when rebuilding domains
- Add wrappers for sched_domains_mutex
- Generalize unique visiting of root domains
- Rebuild root domain accounting after every update
- Remove partition_and_rebuild_sched_domains
- Stop exposing partition_sched_domains_locked
RSEQ: (Michael Jeanson)
- Update kernel fields in lockstep with CONFIG_DEBUG_RSEQ=y
- Fix segfault on registration when rseq_cs is non-zero
- selftests: Add rseq syscall errors test
- selftests: Ensure the rseq ABI TLS is actually 1024 bytes
Membarriers:
- Fix redundant load of membarrier_state (Nysal Jan K.A.)
Scheduler debugging:
- Introduce and use preempt_model_str() (Sebastian Andrzej Siewior)
- Make CONFIG_SCHED_DEBUG unconditional (Ingo Molnar)
Fixes and cleanups:
- Always save/restore x86 TSC sched_clock() on suspend/resume
(Guilherme G. Piccoli)
- Misc fixes and cleanups (Thorsten Blum, Juri Lelli, Sebastian
Andrzej Siewior)"
* tag 'sched-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (40 commits)
cpuidle, sched: Use smp_mb__after_atomic() in current_clr_polling()
sched/debug: Remove CONFIG_SCHED_DEBUG
sched/debug: Remove CONFIG_SCHED_DEBUG from self-test config files
sched/debug, Documentation: Remove (most) CONFIG_SCHED_DEBUG references from documentation
sched/debug: Make CONFIG_SCHED_DEBUG functionality unconditional
sched/debug: Make 'const_debug' tunables unconditional __read_mostly
sched/debug: Change SCHED_WARN_ON() to WARN_ON_ONCE()
rseq/selftests: Fix namespace collision with rseq UAPI header
include/{topology,cpuset}: Move dl_rebuild_rd_accounting to cpuset.h
sched/topology: Stop exposing partition_sched_domains_locked
cgroup/cpuset: Remove partition_and_rebuild_sched_domains
sched/topology: Remove redundant dl_clear_root_domain call
sched/deadline: Rebuild root domain accounting after every update
sched/deadline: Generalize unique visiting of root domains
sched/topology: Wrappers for sched_domains_mutex
sched/deadline: Ignore special tasks when rebuilding domains
tracing: Use preempt_model_str()
xtensa: Rely on generic printing of preemption model
x86: Rely on generic printing of preemption model
s390: Rely on generic printing of preemption model
...
|
|
Pull objtool updates from Ingo Molnar:
- The biggest change is the new option to automatically fail the build
on objtool warnings: CONFIG_OBJTOOL_WERROR.
While there are no currently known unfixed false positives left, such
an expansion in the severity of objtool warnings inevitably creates a
risk of build failures, so it's disabled by default and depends on
!COMPILE_TEST, so it shouldn't be enabled on
allyesconfig/allmodconfig builds and won't be forced on people who
just accept build-time defaults in 'make oldconfig'.
While the option is strongly recommended, only people who enable it
explicitly should see it.
(Josh Poimboeuf)
- Disable branch profiling in noinstr code with a broad brush that
includes all of arch/x86/ and kernel/sched/. (Josh Poimboeuf)
- Create backup object files on objtool errors and print exact objtool
arguments to make failure analysis easier (Josh Poimboeuf)
- Improve noreturn handling (Josh Poimboeuf)
- Improve rodata handling (Tiezhu Yang)
- Support jump tables, switch tables and goto tables on LoongArch
(Tiezhu Yang)
- Misc cleanups and fixes (Josh Poimboeuf, David Engraf, Ingo Molnar)
* tag 'objtool-core-2025-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
tracing: Disable branch profiling in noinstr code
objtool: Use O_CREAT with explicit mode mask
objtool: Add CONFIG_OBJTOOL_WERROR
objtool: Create backup on error and print args
objtool: Change "warning:" to "error:" for --Werror
objtool: Add --Werror option
objtool: Add --output option
objtool: Upgrade "Linked object detected" warning to error
objtool: Consolidate option validation
objtool: Remove --unret dependency on --rethunk
objtool: Increase per-function WARN_FUNC() rate limit
objtool: Update documentation
objtool: Improve __noreturn annotation warning
objtool: Fix error handling inconsistencies in check()
x86/traps: Make exc_double_fault() consistently noreturn
LoongArch: Enable jump table for objtool
objtool/LoongArch: Add support for goto table
objtool/LoongArch: Add support for switch table
objtool: Handle PC relative relocation type
objtool: Handle different entry size of rodata
...
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Pull RCU updates from Boqun Feng:
"Documentation:
- Add broken-timing possibility to stallwarn.rst
- Improve discussion of this_cpu_ptr(), add raw_cpu_ptr()
- Document self-propagating callbacks
- Point call_srcu() to call_rcu() for detailed memory ordering
- Add CONFIG_RCU_LAZY delays to call_rcu() kernel-doc header
- Clarify RCU_LAZY and RCU_LAZY_DEFAULT_OFF help text
- Remove references to old grace-period-wait primitives
srcu:
- Introduce srcu_read_{un,}lock_fast(), which is similar to
srcu_read_{un,}lock_lite(): avoid smp_mb()s in lock and unlock
at the cost of calling synchronize_rcu() in synchronize_srcu()
Moreover, by returning the percpu offset of the counter at
srcu_read_lock_fast() time, srcu_read_unlock_fast() can avoid
extra pointer dereferencing, which makes it faster than
srcu_read_{un,}lock_lite()
srcu_read_{un,}lock_fast() are intended to replace
rcu_read_{un,}lock_trace() if possible
RCU torture:
- Add get_torture_init_jiffies() to return the start time of the test
- Add a test_boost_holdoff module parameter to allow delaying
boosting tests when building rcutorture as built-in
- Add grace period sequence number logging at the beginning and end
of failure/close-call results
- Switch to hexadecimal for the expedited grace period sequence
number in the rcu_exp_grace_period trace point
- Make cur_ops->format_gp_seqs take buffer length
- Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool
- Complain when invalid SRCU reader_flavor is specified
- Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing, which forces SRCU
uses atomics even when percpu ops are NMI safe, and use the Kconfig
for SRCU lockdep testing
Misc:
- Split rcu_report_exp_cpu_mult() mask parameter and use for tracing
- Remove READ_ONCE() for rdp->gpwrap access in __note_gp_changes()
- Fix get_state_synchronize_rcu_full() GP-start detection
- Move RCU Tasks self-tests to core_initcall()
- Print segment lengths in show_rcu_nocb_gp_state()
- Make RCU watch ct_kernel_exit_state() warning
- Flush console log from kernel_power_off()
- rcutorture: Allow a negative value for nfakewriters
- rcu: Update TREE05.boot to test normal synchronize_rcu()
- rcu: Use _full() API to debug synchronize_rcu()
Make RCU handle PREEMPT_LAZY better:
- Fix header guard for rcu_all_qs()
- rcu: Rename PREEMPT_AUTO to PREEMPT_LAZY
- Update __cond_resched comment about RCU quiescent states
- Handle unstable rdp in rcu_read_unlock_strict()
- Handle quiescent states for PREEMPT_RCU=n, PREEMPT_COUNT=y
- osnoise: Provide quiescent states
- Adjust rcutorture with possible PREEMPT_RCU=n && PREEMPT_COUNT=y
combination
- Limit PREEMPT_RCU configurations
- Make rcutorture senario TREE07 and senario TREE10 use
PREEMPT_LAZY=y"
* tag 'rcu-next-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (59 commits)
rcutorture: Make scenario TREE07 build CONFIG_PREEMPT_LAZY=y
rcutorture: Make scenario TREE10 build CONFIG_PREEMPT_LAZY=y
rcu: limit PREEMPT_RCU configurations
rcutorture: Update ->extendables check for lazy preemption
rcutorture: Update rcutorture_one_extend_check() for lazy preemption
osnoise: provide quiescent states
rcu: Use _full() API to debug synchronize_rcu()
rcu: Update TREE05.boot to test normal synchronize_rcu()
rcutorture: Allow a negative value for nfakewriters
Flush console log from kernel_power_off()
context_tracking: Make RCU watch ct_kernel_exit_state() warning
rcu/nocb: Print segment lengths in show_rcu_nocb_gp_state()
rcu-tasks: Move RCU Tasks self-tests to core_initcall()
rcu: Fix get_state_synchronize_rcu_full() GP-start detection
torture: Make SRCU lockdep testing use srcu_read_lock_nmisafe()
srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing
rcutorture: Complain when invalid SRCU reader_flavor is specified
rcutorture: Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool
rcutorture: Make cur_ops->format_gp_seqs take buffer length
rcutorture: Add ftrace-compatible timestamp to GP# failure/close-call output
...
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Pull sched_ext updates from Tejun Heo:
- Add mechanism to count and report internal events. This significantly
improves visibility on subtle corner conditions.
- The default idle CPU selection logic is revamped and improved in
multiple ways including being made topology aware.
- sched_ext was disabling ttwu_queue for simplicity, which can be
costly when hardware topology is more complex. Implement
SCX_OPS_ALLOWED_QUEUED_WAKEUP so that BPF schedulers can selectively
enable ttwu_queue.
- tools/sched_ext updates to improve compatibility among others.
- Other misc updates and fixes.
- sched_ext/for-6.14-fixes were pulled a few times to receive
prerequisite fixes and resolve conflicts.
* tag 'sched_ext-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (42 commits)
sched_ext: idle: Refactor scx_select_cpu_dfl()
sched_ext: idle: Honor idle flags in the built-in idle selection policy
sched_ext: Skip per-CPU tasks in scx_bpf_reenqueue_local()
sched_ext: Add trace point to track sched_ext core events
sched_ext: Change the event type from u64 to s64
sched_ext: Documentation: add task lifecycle summary
tools/sched_ext: Provide a compatible helper for scx_bpf_events()
selftests/sched_ext: Add NUMA-aware scheduler test
tools/sched_ext: Provide consistent access to scx flags
sched_ext: idle: Fix scx_bpf_pick_any_cpu_node() behavior
sched_ext: idle: Introduce scx_bpf_nr_node_ids()
sched_ext: idle: Introduce node-aware idle cpu kfunc helpers
sched_ext: idle: Per-node idle cpumasks
sched_ext: idle: Introduce SCX_OPS_BUILTIN_IDLE_PER_NODE
sched_ext: idle: Make idle static keys private
sched/topology: Introduce for_each_node_numadist() iterator
mm/numa: Introduce nearest_node_nodemask()
nodemask: numa: reorganize inclusion path
nodemask: add nodes_copy()
tools/sched_ext: Sync with scx repo
...
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Add the following tracepoints:
* sched_entry(bool preempt, ip)
Called while entering __schedule
* sched_exit(bool is_switch, ip)
Called while exiting __schedule
* sched_set_state(task, curr_state, state)
Called when a task changes its state (to and from running)
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 <mingo@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/20250305140406.350227-2-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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CONFIG_TRACE_BRANCH_PROFILING inserts a call to ftrace_likely_update()
for each use of likely() or unlikely(). That breaks noinstr rules if
the affected function is annotated as noinstr.
Disable branch profiling for files with noinstr functions. In addition
to some individual files, this also includes the entire arch/x86
subtree, as well as the kernel/entry, drivers/cpuidle, and drivers/idle
directories, all of which are noinstr-heavy.
Due to the nature of how sched binaries are built by combining multiple
.c files into one, branch profiling is disabled more broadly across the
sched code than would otherwise be needed.
This fixes many warnings like the following:
vmlinux.o: warning: objtool: do_syscall_64+0x40: call to ftrace_likely_update() leaves .noinstr.text section
vmlinux.o: warning: objtool: __rdgsbase_inactive+0x33: call to ftrace_likely_update() leaves .noinstr.text section
vmlinux.o: warning: objtool: handle_bug.isra.0+0x198: call to ftrace_likely_update() leaves .noinstr.text section
...
Reported-by: Ingo Molnar <mingo@kernel.org>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/fb94fc9303d48a5ed370498f54500cc4c338eb6d.1742586676.git.jpoimboe@kernel.org
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Pull scheduler fix from Ingo Molnar:
"Revert a scheduler performance optimization that regressed other
workloads"
* tag 'sched-urgent-2025-03-21' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Revert "sched/core: Reduce cost of sched_move_task when config autogroup"
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All the big Linux distros enable CONFIG_SCHED_DEBUG, because
the various features it provides help not just with kernel
development, but with system administration and user-space
software development as well.
Reflect this reality and enable this functionality
unconditionally.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250317104257.3496611-4-mingo@kernel.org
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With CONFIG_SCHED_DEBUG becoming unconditional, remove the
extra 'const_debug' indirection towards __read_mostly.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250317104257.3496611-3-mingo@kernel.org
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The scheduler has this special SCHED_WARN() facility that
depends on CONFIG_SCHED_DEBUG.
Since CONFIG_SCHED_DEBUG is getting removed, convert
SCHED_WARN() to WARN_ON_ONCE().
Note that the warning output isn't 100% equivalent:
#define SCHED_WARN_ON(x) WARN_ONCE(x, #x)
Because SCHED_WARN_ON() would output the 'x' condition
as well, while WARN_ONCE() will only show a backtrace.
Hopefully these are rare enough to not really matter.
If it does, we should probably introduce a new WARN_ON()
variant that outputs the condition in stringified form,
or improve WARN_ON() itself.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250317104257.3496611-2-mingo@kernel.org
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The are no callers of partition_sched_domains_locked() outside
topology.c.
Stop exposing such function.
Suggested-by: Waiman Long <llong@redhat.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Waiman Long <longman@redhat.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/Z9MSC96a8FcqWV3G@jlelli-thinkpadt14gen4.remote.csb
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We completely clean and restore root domains bandwidth accounting after
every root domains change, so the dl_clear_root_domain() call in
partition_sched_domains_locked() is redundant.
Remove it.
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Waiman Long <llong@redhat.com>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Waiman Long <longman@redhat.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/Z9MRtcX4tz4tcLRR@jlelli-thinkpadt14gen4.remote.csb
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Rebuilding of root domains accounting information (total_bw) is
currently broken on some cases, e.g. suspend/resume on aarch64. Problem
is that the way we keep track of domain changes and try to add bandwidth
back is convoluted and fragile.
Fix it by simplify things by making sure bandwidth accounting is cleared
and completely restored after root domains changes (after root domains
are again stable).
To be sure we always call dl_rebuild_rd_accounting while holding
cpuset_mutex we also add cpuset_reset_sched_domains() wrapper.
Fixes: 53916d5fd3c0 ("sched/deadline: Check bandwidth overflow earlier for hotplug")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Co-developed-by: Waiman Long <llong@redhat.com>
Signed-off-by: Waiman Long <llong@redhat.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/Z9MRfeJKJUOyUSto@jlelli-thinkpadt14gen4.remote.csb
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Bandwidth checks and updates that work on root domains currently employ
a cookie mechanism for efficiency. This mechanism is very much tied to
when root domains are first created and initialized.
Generalize the cookie mechanism so that it can be used also later at
runtime while updating root domains. Also, additionally guard it with
sched_domains_mutex, since domains need to be stable while updating them
(and it will be required for further dynamic changes).
Fixes: 53916d5fd3c0 ("sched/deadline: Check bandwidth overflow earlier for hotplug")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Waiman Long <longman@redhat.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/Z9MQaiXPvEeW_v7x@jlelli-thinkpadt14gen4.remote.csb
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Create wrappers for sched_domains_mutex so that it can transparently be
used on both CONFIG_SMP and !CONFIG_SMP, as some function will need to
do.
Fixes: 53916d5fd3c0 ("sched/deadline: Check bandwidth overflow earlier for hotplug")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Waiman Long <longman@redhat.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/Z9MP5Oq9RB8jBs3y@jlelli-thinkpadt14gen4.remote.csb
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SCHED_DEADLINE special tasks get a fake bandwidth that is only used to
make sure sleeping and priority inheritance 'work', but it is ignored
for runtime enforcement and admission control.
Be consistent with it also when rebuilding root domains.
Fixes: 53916d5fd3c0 ("sched/deadline: Check bandwidth overflow earlier for hotplug")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Waiman Long <longman@redhat.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20250313170011.357208-2-juri.lelli@redhat.com
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The individual architectures often add the preemption model to the begin
of the backtrace. This is the case on X86 or ARM64 for the "die" case
but not for regular warning. With the addition of DYNAMIC_PREEMPT for
PREEMPT_RT we end up with CONFIG_PREEMPT and CONFIG_PREEMPT_RT set
simultaneously. That means that everyone who tried to add that piece of
information gets it wrong for PREEMPT_RT because PREEMPT is checked
first.
Provide a generic function which returns the current scheduling model
considering LAZY preempt and the current state of PREEMPT_DYNAMIC.
The resulting strings are:
┏━━━━━━━━━━━┳━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━┓
┃ Model ┃ -RT -DYN ┃ +RT -DYN ┃ -RT +DYN ┃ +RT +DYN ┃
┡━━━━━━━━━━━╇━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━┩
│NONE │ NONE │ n/a │ PREEMPT(none) │ n/a │
├───────────┼──────────────┼───────────────────┼────────────────────┼───────────────────┤
│VOLUNTARY │ VOLUNTARY │ n/a │ PREEMPT(voluntary) │ n/a │
├───────────┼──────────────┼───────────────────┼────────────────────┼───────────────────┤
│FULL │ PREEMPT │ PREEMPT_RT │ PREEMPT(full) │ PREEMPT_{RT,full} │
├───────────┼──────────────┼───────────────────┼────────────────────┼───────────────────┤
│LAZY │ PREEMPT_LAZY │ PREEMPT_{RT,LAZY} │ PREEMPT(lazy) │ PREEMPT_{RT,lazy} │
└───────────┴──────────────┴───────────────────┴────────────────────┴───────────────────┘
[ The dynamic building of the string can lead to an empty string if the
function is invoked simultaneously on two CPUs. ]
Co-developed-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Co-developed-by: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Signed-off-by: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Link: https://lore.kernel.org/r/20250314160810.2373416-2-bigeasy@linutronix.de
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This reverts commit eff6c8ce8d4d7faef75f66614dd20bb50595d261.
Hazem reported a 30% drop in UnixBench spawn test with commit
eff6c8ce8d4d ("sched/core: Reduce cost of sched_move_task when config
autogroup") on a m6g.xlarge AWS EC2 instance with 4 vCPUs and 16 GiB RAM
(aarch64) (single level MC sched domain):
https://lkml.kernel.org/r/20250205151026.13061-1-hagarhem@amazon.com
There is an early bail from sched_move_task() if p->sched_task_group is
equal to p's 'cpu cgroup' (sched_get_task_group()). E.g. both are
pointing to taskgroup '/user.slice/user-1000.slice/session-1.scope'
(Ubuntu '22.04.5 LTS').
So in:
do_exit()
sched_autogroup_exit_task()
sched_move_task()
if sched_get_task_group(p) == p->sched_task_group
return
/* p is enqueued */
dequeue_task() \
sched_change_group() |
task_change_group_fair() |
detach_task_cfs_rq() | (1)
set_task_rq() |
attach_task_cfs_rq() |
enqueue_task() /
(1) isn't called for p anymore.
Turns out that the regression is related to sgs->group_util in
group_is_overloaded() and group_has_capacity(). If (1) isn't called for
all the 'spawn' tasks then sgs->group_util is ~900 and
sgs->group_capacity = 1024 (single CPU sched domain) and this leads to
group_is_overloaded() returning true (2) and group_has_capacity() false
(3) much more often compared to the case when (1) is called.
I.e. there are much more cases of 'group_is_overloaded' and
'group_fully_busy' in WF_FORK wakeup sched_balance_find_dst_cpu() which
then returns much more often a CPU != smp_processor_id() (5).
This isn't good for these extremely short running tasks (FORK + EXIT)
and also involves calling sched_balance_find_dst_group_cpu() unnecessary
(single CPU sched domain).
Instead if (1) is called for 'p->flags & PF_EXITING' then the path
(4),(6) is taken much more often.
select_task_rq_fair(..., wake_flags = WF_FORK)
cpu = smp_processor_id()
new_cpu = sched_balance_find_dst_cpu(..., cpu, ...)
group = sched_balance_find_dst_group(..., cpu)
do {
update_sg_wakeup_stats()
sgs->group_type = group_classify()
if group_is_overloaded() (2)
return group_overloaded
if !group_has_capacity() (3)
return group_fully_busy
return group_has_spare (4)
} while group
if local_sgs.group_type > idlest_sgs.group_type
return idlest (5)
case group_has_spare:
if local_sgs.idle_cpus >= idlest_sgs.idle_cpus
return NULL (6)
Unixbench Tests './Run -c 4 spawn' on:
(a) VM AWS instance (m7gd.16xlarge) with v6.13 ('maxcpus=4 nr_cpus=4')
and Ubuntu 22.04.5 LTS (aarch64).
Shell & test run in '/user.slice/user-1000.slice/session-1.scope'.
w/o patch w/ patch
21005 27120
(b) i7-13700K with tip/sched/core ('nosmt maxcpus=8 nr_cpus=8') and
Ubuntu 22.04.5 LTS (x86_64).
Shell & test run in '/A'.
w/o patch w/ patch
67675 88806
CONFIG_SCHED_AUTOGROUP=y & /sys/proc/kernel/sched_autogroup_enabled equal
0 or 1.
Reported-by: Hazem Mohamed Abuelfotoh <abuehaze@amazon.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Hagar Hemdan <hagarhem@amazon.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250314151345.275739-1-dietmar.eggemann@arm.com
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Repeat calls of static_branch_enable() to an already enabled
static key introduce overhead, because it calls cpus_read_lock().
Users may frequently set the uclamp value of tasks, triggering
the repeat enabling of the sched_uclamp_used static key.
Optimize this and avoid repeat calls to static_branch_enable()
by checking whether it's enabled already.
[ mingo: Rewrote the changelog for legibility ]
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20250219093747.2612-2-xuewen.yan@unisoc.com
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Don't open-code static_branch_unlikely(&sched_uclamp_used), we have
the uclamp_is_used() wrapper around it.
[ mingo: Clean up the changelog ]
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Hongyan Xia <hongyan.xia2@arm.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20250219093747.2612-1-xuewen.yan@unisoc.com
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Pull scheduler fix from Ingo Molnar:
"Fix a sleeping-while-atomic bug caused by a recent optimization
utilizing static keys that didn't consider that the
static_key_disable() call could be triggered in atomic context.
Revert the optimization"
* tag 'sched-urgent-2025-03-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/clock: Don't define sched_clock_irqtime as static key
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Make scx_select_cpu_dfl() more consistent with the other idle-related
APIs by returning a negative value when an idle CPU isn't found.
No functional changes, this is purely a refactoring.
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
|
|
Enable passing idle flags (%SCX_PICK_IDLE_*) to scx_select_cpu_dfl(),
to enforce strict selection criteria, such as selecting an idle CPU
strictly within @prev_cpu's node or choosing only a fully idle SMT core.
This functionality will be exposed through a dedicated kfunc in a
separate patch.
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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scx_bpf_reenqueue_local() can be invoked from ops.cpu_release() to give
tasks that are queued to the local DSQ a chance to migrate to other
CPUs, when a CPU is taken by a higher scheduling class.
However, there is no point re-enqueuing tasks that can only run on that
particular CPU, as they would simply be re-added to the same local DSQ
without any benefit.
Therefore, skip per-CPU tasks in scx_bpf_reenqueue_local().
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull sched_ext fix from Tejun Heo:
"BPF schedulers could trigger a crash by passing in an invalid CPU to
the scx_bpf_select_cpu_dfl() helper.
Fix it by verifying input validity"
* tag 'sched_ext-for-6.14-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()
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Linus Torvalds
Tejun Heo
Andrea Righi
Omar Sandoval
Rafael J. Wysocki
Breno Leitao
Thomas Gleixner
Mathieu Desnoyers
Jake Hillion
Gabriele Monaco
Josh Poimboeuf
Ingo Molnar
Juri Lelli
Sebastian Andrzej Siewior
Dietmar Eggemann
Xuewen Yan