linux-kernel - [PREEMPT_RT] bogus lockdep assert from i915 on v5.2-rt1

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Date:   Tue, 16 Jul 2019 14:50:43 -0500
From:   Clark Williams <williams@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        RT <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PREEMPT_RT] bogus lockdep assert from i915 on v5.2-rt1

Thomas,

When looking at a problem on v5.2-rt1, I turned on lockdep and started getting warnings
from lockdep_assert_irqs_disabled() in the i915 driver. They're making these calls inside
a spin_lock_irqsave/spin_lock_irqrestore block, which of course doesn't fiddle with IRQs
when PREEMPT_RT is configured. The attached patch places the three calls inside
if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL)) blocks, so should avoid the bogus warning on RT.

Clark

-- 
The United States Coast Guard
Ruining Natural Selection since 1790

View attachment "0001-i915-avoid-calling-lockdep_assert_irqs_disabled-on-P.patch" of type "text/x-patch" (1952 bytes)