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From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: A question of sleeping with interrupts are disabled in start_kernel()
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Message-ID: <1eb16c24-ef3b-2962-d216-57f66321035e@gmail.com>
Date:   Fri, 6 Apr 2018 17:53:21 +0800
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Hello,

I have a question of the call path init/main.c:
init/main.c: start_kernel() ->
kernel/events/core.c: perf_pmu_register() ->
kernel/events/core.c: perf_event_init() ->
kernel/events/core.c: pmu_dev_alloc()

In this call path, start_kernel() calls local_irq_disable() to disable 
the interrupt;
perf_pmu_register() calls mutex_lock() and idr_alloc(GFP_KERNEL), and 
they can sleep;
pmu_dev_alloc() calls kzalloc(GFP_KERNEL), and it can sleep.

In my opinion, this code may sleep with interrupts are disabled.
I wonder why this code is okay?


Best wishes,
Jia-Ju Bai