From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-arm-kernel@lists.infradead.org,
linux-rt-devel@lists.linux.dev, Arnd Bergmann <arnd@arndb.de>,
Linus Walleij <linus.walleij@linaro.org>,
"Yadi.hu" <yadi.hu@windriver.com>, Bryan Brattlof <bb@ti.com>
Subject: Re: [PATCH v4 1/2] ARM: mm: fault: Enable interrupts before invoking __do_user_fault()
Date: Fri, 16 Jan 2026 17:33:48 +0000 [thread overview]
Message-ID: <aWp2fKGfIQKJ8wze@shell.armlinux.org.uk> (raw)
In-Reply-To: <20260116170041.1059997-2-bigeasy@linutronix.de>
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.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
next prev parent reply other threads:[~2026-01-16 17:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-16 17:00 [PATCH v4 0/2] ARM: Remaining PREEMPT_RT bits Sebastian Andrzej Siewior
2026-01-16 17:00 ` [PATCH v4 1/2] ARM: mm: fault: Enable interrupts before invoking __do_user_fault() Sebastian Andrzej Siewior
2026-01-16 17:33 ` Russell King (Oracle) [this message]
2026-01-16 18:12 ` Sebastian Andrzej Siewior
2026-01-16 20:01 ` Russell King (Oracle)
2026-01-16 20:07 ` Russell King (Oracle)
2026-01-16 20:09 ` Russell King (Oracle)
2026-01-16 20:30 ` Sebastian Andrzej Siewior
2026-01-16 17:00 ` [PATCH v4 2/2] ARM: Allow to enable RT Sebastian Andrzej Siewior
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