Fix rcuog kthread wakeup invocation from softirq context on a CPU
which has been marked offline. This can happen when new callbacks
are enqueued from a softirq on an offline CPU before it calls
rcutree_report_cpu_dead(). When this happens on NOCB configuration,
the rcuog wake-up is deferred through an IPI to an online CPU.
This is done to avoid call into the scheduler which can risk
arming the RT-bandwidth after hrtimers have been migrated out
and disabled. However, doing IPI call from softirq is not allowed
Fix this by forcing deferred rcuog wakeup through the NOCB timer
when the CPU is offline.
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Merge tag 'rcu.fixes.6.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux
Pull RCU fix from Neeraj Upadhyay:
"Fix rcuog kthread wakeup invocation from softirq context on a CPU
which has been marked offline.
This can happen when new callbacks are enqueued from a softirq on an
offline CPU before it calls rcutree_report_cpu_dead(). When this
happens on NOCB configuration, the rcuog wake-up is deferred through
an IPI to an online CPU. This is done to avoid call into the scheduler
which can risk arming the RT-bandwidth after hrtimers have been
migrated out and disabled.
However, doing IPI call from softirq is not allowed: Fix this by
forcing deferred rcuog wakeup through the NOCB timer when the CPU is
offline"
* tag 'rcu.fixes.6.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux:
rcu/nocb: Fix rcuog wake-up from offline softirq
a1029768f3