From: Sebastian Andrzej Siewior Date: Tue, 11 Dec 2018 21:53:43 +0100 Subject: [PATCH 087/342] x86/mm/pat: disable preemption __split_large_page() after spin_lock() Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=ee35c399cafe97f822c232c385f3e5be619dbe9e 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 __flush_tlb_all(). Signed-off-by: Sebastian Andrzej Siewior --- arch/x86/mm/pageattr.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 101f3ad0d6ad..0b0396261ca1 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -687,12 +687,18 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address, pgprot_t ref_prot; spin_lock(&pgd_lock); + /* + * Keep preemption disabled after __flush_tlb_all() which expects not be + * preempted during the flush of the local TLB. + */ + preempt_disable(); /* * Check for races, another CPU might have split this page * up for us already: */ tmp = _lookup_address_cpa(cpa, address, &level); if (tmp != kpte) { + preempt_enable(); spin_unlock(&pgd_lock); return 1; } @@ -726,6 +732,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address, break; default: + preempt_enable(); spin_unlock(&pgd_lock); return 1; } @@ -764,6 +771,7 @@ __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;