Messages in this thread | | | Date | Sun, 20 Nov 2016 23:52:07 +0600 | From | Alexnader Kuleshov <> | Subject | Question: goal of twice disabling of preemption in exception handlers |
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Hello everyone,
Exception handlers which may run on IST stack disable and enable preemption twice. For example do_int3() [1]. This one calls ist_enter() which disables preemption with preempt_disable() every time without any conditions. And later do_int3() calls preempt_disable() again [2] before do_trap().
Of course we decrement preemption counter in the end of such exception handlers twice too. But what's actual purpose of doing this two times?
[1] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/arch/x86/kernel/traps.c?id=refs/tags/next-20161117#n530 [2] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/arch/x86/kernel/traps.c?id=refs/tags/next-20161117#n566
Thank you.
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