timers/migration: Fix hotplug migrator selection target on asymetric capacity machines

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When a top-level migrator is deactivated, either at CPU down hotplug time
or when a CPU is domain isolated, a new migrator is elected among the
available CPUs and woken up to take over the migration duty.

However that election must happen at the scope of a given hierarchy and not
globally, which the introduction of per-capacity hierarchies failed to
handle.

As a result a given hierarchy may end up without migrator to handle global
timers.

Fix it by making sure that the new migrator belongs to the same hierarchy
as the outgoing CPU.

Fixes: 098cbaad8e ("timers/migration: Split per-capacity hierarchies")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260519220926.63437-2-frederic@kernel.org

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Frederic Weisbecker 2026-05-20 00:09:25 +02:00 • committed by Thomas Gleixner

parent 180a232ea7

commit e4a70f5fbd

1 changed files with 32 additions and 10 deletions

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kernel/time/timer_migration.c

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