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printk/nbcon: Add a scheduling point to nbcon_kthread_func().

Derek Barbosa requested to merge debarbos/centos-stream-9:printklockup into main

JIRA: https://issues.redhat.com/browse/RHEL-37526

Upstream Status: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git

commit 2cd745fc0bec9bad3bd8a6fc14e34c3497d2b0c9

Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Date:   Thu Jun 20 11:21:13 2024 +0200

    prinkt/nbcon: Add a scheduling point to nbcon_kthread_func().

    Constant printing can lead to a CPU hog in nbcon_kthread_func(). The
    context is preemptible but on !PREEMPT kernels there is no explicit
    preemption point which leads softlockup warnings.

    Add an explicit preemption point in nbcon_kthread_func().

    Reported-by: Derek Barbosa <debarbos@redhat.com>
    Link: https://lore.kernel.org/ZnHF5j1DUDjN1kkq@debarbos-thinkpadt14sgen2i.remote.csb
    Reviewed-by: John Ogness <john.ogness@linutronix.de>
    Acked-by: Andrew Halaney <ahalaney@redhat.com>
    Tested-by: Andrew Halaney <ahalaney@redhat.com>
    Acked-by: Derek Barbosa <debarbos@redhat.com>
    Tested-by: Derek Barbosa <debarbos@redhat.com>
    Link: https://lore.kernel.org/r/20240620094300.YJlW043f@linutronix.de
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Signed-off-by: Clark Williams <clark.williams@gmail.com>

Signed-off-by: Derek Barbosa debarbos@redhat.com

Edited by Derek Barbosa

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