[PATCH 6/9] x86/paravirt: allow preemption with lazy mmu mode

Jeremy Fitzhardinge
2009-02-18T22:31:04Z

Lift restrictions on preemption with lazy mmu mode, as it is now allowed.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
arch/x86/kernel/paravirt.c | 7 ++++---
arch/x86/xen/mmu.c | 8 +-------
2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 554dadd..1a81ce9 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -248,7 +248,6 @@ static DEFINE_PER_CPU(enum paravirt_lazy_mode, paravirt_lazy_mode) = PARAVIRT_LA
static inline void enter_lazy(enum paravirt_lazy_mode mode)
{
BUG_ON(__get_cpu_var(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);
- BUG_ON(preemptible());

__get_cpu_var(paravirt_lazy_mode) = mode;
}
@@ -256,7 +255,6 @@ static inline void enter_lazy(enum paravirt_lazy_mode mode)
static void leave_lazy(enum paravirt_lazy_mode mode)
{
BUG_ON(__get_cpu_var(paravirt_lazy_mode) != mode);
- BUG_ON(preemptible());

__get_cpu_var(paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;
}
@@ -273,6 +271,8 @@ void paravirt_leave_lazy_mmu(void)

void paravirt_enter_lazy_cpu(void)
{
+ BUG_ON(preemptible());
+
if (percpu_read(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU) {
arch_leave_lazy_mmu_mode();
set_thread_flag(TIF_LAZY_MMU_UPDATES);
@@ -282,6 +282,8 @@ void paravirt_enter_lazy_cpu(void)

void paravirt_leave_lazy_cpu(void)
{
+ BUG_ON(preemptible());
+
leave_lazy(PARAVIRT_LAZY_CPU);

if (test_and_clear_thread_flag(TIF_LAZY_MMU_UPDATES))
@@ -301,7 +303,6 @@ void arch_flush_lazy_mmu_mode(void)
preempt_disable();

if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
- WARN_ON(preempt_count() == 1);
arch_leave_lazy_mmu_mode();
arch_enter_lazy_mmu_mode();
}
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 2669c58..92c6463 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -412,10 +412,6 @@ void set_pte_mfn(unsigned long vaddr, unsigned long mfn, pgprot_t flags)
void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pteval)
{
- /* updates to init_mm may be done without lock */
- if (mm == &init_mm)
- preempt_disable();
-
ADD_STATS(set_pte_at, 1);
// ADD_STATS(set_pte_at_pinned, xen_page_pinned(ptep));
ADD_STATS(set_pte_at_current, mm == current->mm);
@@ -436,9 +432,7 @@ void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
}
xen_set_pte(ptep, pteval);

-out:
- if (mm == &init_mm)
- preempt_enable();
+out: return;
}

pte_t xen_ptep_modify_prot_start(struct mm_struct *mm,
--
1.6.0.6