On Thu, 13 Dec 2018 17:44:31 +0100 Sebastian Andrzej Siewior <[email protected]> wrote:
> 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(). I'm guessing the reason for the warn on is that we don't want a task to be scheduled in where we expected the TLB to have been flushed. > > Signed-off-by: Sebastian Andrzej Siewior <[email protected]> > --- > 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); We probably should have comment explaining why we have a preempt_disable here. > + 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(); Shouldn't the preempt_enable() be before the unlock? > 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(); Here too. -- Steve > 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;
