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Commit 6a942f57 authored by Valentin Schneider's avatar Valentin Schneider Committed by Vasily Gorbik
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s390: preempt: Fix preempt_count initialization



S390's init_idle_preempt_count(p, cpu) doesn't actually let us initialize the
preempt_count of the requested CPU's idle task: it unconditionally writes
to the current CPU's. This clearly conflicts with idle_threads_init(),
which intends to initialize *all* the idle tasks, including their
preempt_count (or their CPU's, if the arch uses a per-CPU preempt_count).

Unfortunately, it seems the way s390 does things doesn't let us initialize
every possible CPU's preempt_count early on, as the pages where this
resides are only allocated when a CPU is brought up and are freed when it
is brought down.

Let the arch-specific code set a CPU's preempt_count when its lowcore is
allocated, and turn init_idle_preempt_count() into an empty stub.

Fixes: f1a0a376 ("sched/core: Initialize the idle task with preemption disabled")
Reported-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Tested-by: default avatarGuenter Roeck <linux@roeck-us.net>
Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/r/20210707163338.1623014-1-valentin.schneider@arm.com


Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 4ee471fe
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