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arm: Disable FAST_GUP on PREEMPT_RT if HIGHPTE is also enabled.

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BugLink: https://bugs.launchpad.net/bugs/2060704

gup_pgd_range() is invoked with disabled interrupts and invokes
__kmap_local_page_prot() via pte_offset_map(), gup_p4d_range().
With HIGHPTE enabled, __kmap_local_page_prot() invokes kmap_high_get()
which uses a spinlock_t via lock_kmap_any(). This leads to an
sleeping-while-atomic error on PREEMPT_RT because spinlock_t becomes a
sleeping lock and must not be acquired in atomic context.

The loop in map_new_virtual() uses wait_queue_head_t for wake up which
also is using a spinlock_t.

Limit HAVE_FAST_GUP additionaly to remain disabled on PREEMPT_RT with
HIGHPTE enabled.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Kevin Becker <kevin.becker@canonical.com>
This commit is contained in:
Sebastian Andrzej Siewior
2024-01-23 12:56:21 +01:00
committed by Kevin Becker
parent c2b5cd169d
commit 8e81ad948b
1 changed files with 1 additions and 1 deletions
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arch/arm/Kconfig
+1 -1
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@@ -98,7 +98,7 @@ config ARM
select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU
select HAVE_EXIT_THREAD
select HAVE_FAST_GUP if ARM_LPAE
select HAVE_FAST_GUP if ARM_LPAE && !(PREEMPT_RT && HIGHPTE)
select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_FUNCTION_GRAPH_TRACER