linux-kernel - begger help for this comment about intel

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Date:	Sun, 10 Apr 2016 00:34:26 +0800
From:	赵瑞哲 <ruizhe.zhao.g@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: begger help for this comment about intel_cacheinfo.c

in this commit

https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/arch/x86/kernel/cpu/intel_cacheinfo.c?id=b2bb85549134c005e997e5a7ed303bda6a1ae738

Mike wrote:
> We should not try to save and restore cpus_allowed on current. We can't use work_on_cpu() here, > since it's in the hotplug cpu path (if anyone else tries to get the hotplug lock from a workqueue we > could deadlock against them). Fortunately, we can just use smp_call_function_single() since the > function can run from an interrupt.

but I really can't understand that how the deadlock works.

anyone can give some hints?

any response is appreiated :)