Re: [PATCH v4 1/2] ARM: mm: fault: Enable interrupts before invoking __do_user_fault()

Russell King (Oracle)
2026-01-16T17:34:01Z

On Fri, Jan 16, 2026 at 06:00:40PM +0100, Sebastian Andrzej Siewior wrote:
> From: "Yadi.hu" <yadi.hu@windriver.com>
>
> A page fault from userland for a kernel address originates from from
> do_sect_fault() (!LPAE) or do_page_fault() and ends in __do_user_fault()
> by sending a signal.
>
> Sending a signal requires to acquire sighand_struct::siglock which is a
> spinlock_t. On PREEMPT_RT spinlock_t becomes a sleeping spin lock which
> requires interrupts to be enabled. Since the calling context is user
> land, interrupts must have been enabled so it is fine to enable them in
> this case.
>
> Enable interrupts in do_kernel_address_page_fault() unconditional in the
> user_mode case().
> Enable interrupts in do_sect_fault() if they were previously enabled.

Do you need any of this? __do_user_fault() now calls
local_irq_enable() as almost the first thing it does.

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