genirq: Add IRQF_NO_AUTOEN for request_irq/nmi()

mainline inclusion
from mainline-v5.12-rc2
commit cbe16f35
category: bugfix
bugzilla: 175148
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cbe16f35bee6880becca6f20d2ebf6b457148552



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Many drivers don't want interrupts enabled automatically via request_irq().
So they are handling this issue by either way of the below two:

(1)
  irq_set_status_flags(irq, IRQ_NOAUTOEN);
  request_irq(dev, irq...);

(2)
  request_irq(dev, irq...);
  disable_irq(irq);

The code in the second way is silly and unsafe. In the small time gap
between request_irq() and disable_irq(), interrupts can still come.

The code in the first way is safe though it's subobtimal.

Add a new IRQF_NO_AUTOEN flag which can be handed in by drivers to
request_irq() and request_nmi(). It prevents the automatic enabling of the
requested interrupt/nmi in the same safe way as #1 above. With that the
various usage sites of #1 and #2 above can be simplified and corrected.

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: dmitry.torokhov@gmail.com
Link: https://lore.kernel.org/r/20210302224916.13980-2-song.bao.hua@hisilicon.com


Reviewed-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>