Re: [PATCH v5 1/2] ARM: mm: fault: Enable interrupts before invoking __do_user_fault()

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Thu, Feb 26, 2026 at 12:17:41PM +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.
> 
> [bigeasy: Initial patch/ report by Yadi. Maintained the patch and redid
>           the patch description since]
> 
> Signed-off-by: Yadi.hu <yadi.hu@windriver.com>
> Acked-by: Linus Walleij <linus.walleij@linaro.org>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Sorry, I've been swamped with stmmac for ages, which has become a
millstone.

I need to push out these patches:

ARM: provide individual is_translation_fault() and is_permission_fault()
ARM: move FSR fault status definitions before fsr_fs()
ARM: use BIT() and GENMASK() for fault status register fields
ARM: move is_permission_fault() and is_translation_fault() to fault.h
ARM: move vmalloc() lazy-page table population
ARM: ensure interrupts are enabled in __do_user_fault()

which will address some of your issues, and clean up the fault handling
code. These patches all date from 5th December. :/

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!