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authorPeter Zijlstra <peterz@infradead.org>2017-09-20 19:00:18 +0200
committerThomas Gleixner <tglx@linutronix.de>2017-09-25 22:11:43 +0200
commit724a86881d03ee5794148e65142e24ed3621be66 (patch)
treec0e54518b981d521c526e53f88013c300a22ec42 /arch/arm/lib/xor-neon.c
parent4dddfb5faa6118564b0c54a163353d13882299d8 (diff)
smp/hotplug: Callback vs state-machine consistency
While the generic callback functions have an 'int' return and thus appear to be allowed to return error, this is not true for all states. Specifically, what used to be STARTING/DYING are ran with IRQs disabled from critical parts of CPU bringup/teardown and are not allowed to fail. Add WARNs to enforce this rule. But since some callbacks are indeed allowed to fail, we have the situation where a state-machine rollback encounters a failure, in this case we're stuck, we can't go forward and we can't go back. Also add a WARN for that case. AFAICT this is a fundamental 'problem' with no real obvious solution. We want the 'prepare' callbacks to allow failure on either up or down. Typically on prepare-up this would be things like -ENOMEM from resource allocations, and the typical usage in prepare-down would be something like -EBUSY to avoid CPUs being taken away. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: bigeasy@linutronix.de Cc: efault@gmx.de Cc: rostedt@goodmis.org Cc: max.byungchul.park@gmail.com Link: https://lkml.kernel.org/r/20170920170546.819539119@infradead.org
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