This is a note to let you know that I've just added the patch titled
sched: Optimize migration_cpu_stop()
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-optimize-migration_cpu_stop.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3f1bc119cd7fc987c8ed25ffb717f99403bb308c Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Wed, 24 Feb 2021 11:21:35 +0100
Subject: sched: Optimize migration_cpu_stop()
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit 3f1bc119cd7fc987c8ed25ffb717f99403bb308c upstream.
When the purpose of migration_cpu_stop() is to migrate the task to
'any' valid CPU, don't migrate the task when it's already running on a
valid CPU.
Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@xxxxxxxxxx
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx>
Link: https://lkml.kernel.org/r/20210224131355.569238629@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/core.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1936,14 +1936,25 @@ static int migration_cpu_stop(void *data
complete = true;
}
- if (dest_cpu < 0)
+ if (dest_cpu < 0) {
+ if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
+ goto out;
+
dest_cpu = cpumask_any_distribute(&p->cpus_mask);
+ }
if (task_on_rq_queued(p))
rq = __migrate_task(rq, &rf, p, dest_cpu);
else
p->wake_cpu = dest_cpu;
+ /*
+ * XXX __migrate_task() can fail, at which point we might end
+ * up running on a dodgy CPU, AFAICT this can only happen
+ * during CPU hotplug, at which point we'll get pushed out
+ * anyway, so it's probably not a big deal.
+ */
+
} else if (pending) {
/*
* This happens when we get migrated between migrate_enable()'s
Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are
queue-5.11/powerpc-perf-fix-handling-of-privilege-level-checks-in-perf-interrupt-context.patch
queue-5.11/sched-fix-migration_cpu_stop-requeueing.patch
queue-5.11/sched-simplify-set_affinity_pending-refcounts.patch
queue-5.11/perf-traceevent-ensure-read-cmdlines-are-null-terminated.patch
queue-5.11/perf-core-flush-pmu-internal-buffers-for-per-cpu-eve.patch
queue-5.11/sched-simplify-migration_cpu_stop.patch
queue-5.11/sched-membarrier-fix-missing-local-execution-of-ipi_sync_rq_state.patch
queue-5.11/x86-unwind-orc-disable-kasan-checking-in-the-orc-unwinder-part-2.patch
queue-5.11/arm64-perf-fix-64-bit-event-counter-read-truncation.patch
queue-5.11/sched-collate-affine_move_task-stoppers.patch
queue-5.11/sched-fix-affine_move_task-self-concurrency.patch
queue-5.11/stop_machine-mark-helpers-__always_inline.patch
queue-5.11/seqlock-lockdep-fix-seqcount_latch_init.patch
queue-5.11/sched-optimize-migration_cpu_stop.patch
queue-5.11/perf-build-fix-ccache-usage-in-cc-when-generating-arch-errno-table.patch
queue-5.11/mm-userfaultfd-fix-memory-corruption-due-to-writeprotect.patch
queue-5.11/perf-x86-intel-set-perf_attach_sched_cb-for-large-pe.patch
