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Subject[PATCH RT] x86/mm/pat: disable preemption __split_large_page() after spin_lock()
Commit "x86/mm/pat: Disable preemption around __flush_tlb_all()" added a
warning if __flush_tlb_all() is invoked in preemptible context. On !RT
the warning does not trigger because a spin lock is acquired which
disables preemption. On RT the spin lock does not disable preemption and
so the warning is seen.

Disable preemption to avoid the warning in __flush_tlb_all().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/mm/pageattr.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index e2d4b25c7aa44..abbe3e93ec266 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -687,6 +687,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
pgprot_t ref_prot;

spin_lock(&pgd_lock);
+ preempt_disable();
/*
* Check for races, another CPU might have split this page
* up for us already:
@@ -694,6 +695,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
tmp = _lookup_address_cpa(cpa, address, &level);
if (tmp != kpte) {
spin_unlock(&pgd_lock);
+ preempt_enable();
return 1;
}

@@ -727,6 +729,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,

default:
spin_unlock(&pgd_lock);
+ preempt_enable();
return 1;
}

@@ -764,6 +767,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
* going on.
*/
__flush_tlb_all();
+ preempt_enable();
spin_unlock(&pgd_lock);

return 0;
--
2.20.0
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