[S390] fix tlb flushing vs. concurrent /proc accesses
The tlb flushing code uses the mm_users field of the mm_struct to
decide if each page table entry needs to be flushed individually with
IPTE or if a global flush for the mm_struct is sufficient after all page
table updates have been done. The comment for mm_users says "How many
users with user space?" but the /proc code increases mm_users after it
found the process structure by pid without creating a new user process.
Which makes mm_users useless for the decision between the two tlb
flusing methods. The current code can be confused to not flush tlb
entries by a concurrent access to /proc files if e.g. a fork is in
progres. The solution for this problem is to make the tlb flushing
logic independent from the mm_users field.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/hugetlb.h b/arch/s390/include/asm/hugetlb.h
index 670a1d1..bb8343d 100644
--- a/arch/s390/include/asm/hugetlb.h
+++ b/arch/s390/include/asm/hugetlb.h
@@ -97,6 +97,7 @@
{
pte_t pte = huge_ptep_get(ptep);
+ mm->context.flush_mm = 1;
pmd_clear((pmd_t *) ptep);
return pte;
}
@@ -167,7 +168,8 @@
({ \
pte_t __pte = huge_ptep_get(__ptep); \
if (pte_write(__pte)) { \
- if (atomic_read(&(__mm)->mm_users) > 1 || \
+ (__mm)->context.flush_mm = 1; \
+ if (atomic_read(&(__mm)->context.attach_count) > 1 || \
(__mm) != current->active_mm) \
huge_ptep_invalidate(__mm, __addr, __ptep); \
set_huge_pte_at(__mm, __addr, __ptep, \
diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index 99e3409..78522cde 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -2,6 +2,8 @@
#define __MMU_H
typedef struct {
+ atomic_t attach_count;
+ unsigned int flush_mm;
spinlock_t list_lock;
struct list_head crst_list;
struct list_head pgtable_list;
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index 976e273..a6f0e7c 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -11,11 +11,14 @@
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
+#include <asm/tlbflush.h>
#include <asm-generic/mm_hooks.h>
static inline int init_new_context(struct task_struct *tsk,
struct mm_struct *mm)
{
+ atomic_set(&mm->context.attach_count, 0);
+ mm->context.flush_mm = 0;
mm->context.asce_bits = _ASCE_TABLE_LENGTH | _ASCE_USER_BITS;
#ifdef CONFIG_64BIT
mm->context.asce_bits |= _ASCE_TYPE_REGION3;
@@ -76,6 +79,12 @@
{
cpumask_set_cpu(smp_processor_id(), mm_cpumask(next));
update_mm(next, tsk);
+ atomic_dec(&prev->context.attach_count);
+ WARN_ON(atomic_read(&prev->context.attach_count) < 0);
+ atomic_inc(&next->context.attach_count);
+ /* Check for TLBs not flushed yet */
+ if (next->context.flush_mm)
+ __tlb_flush_mm(next);
}
#define enter_lazy_tlb(mm,tsk) do { } while (0)
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 89a504c..3157441 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -880,7 +880,8 @@
#define ptep_get_and_clear(__mm, __address, __ptep) \
({ \
pte_t __pte = *(__ptep); \
- if (atomic_read(&(__mm)->mm_users) > 1 || \
+ (__mm)->context.flush_mm = 1; \
+ if (atomic_read(&(__mm)->context.attach_count) > 1 || \
(__mm) != current->active_mm) \
ptep_invalidate(__mm, __address, __ptep); \
else \
@@ -923,7 +924,8 @@
({ \
pte_t __pte = *(__ptep); \
if (pte_write(__pte)) { \
- if (atomic_read(&(__mm)->mm_users) > 1 || \
+ (__mm)->context.flush_mm = 1; \
+ if (atomic_read(&(__mm)->context.attach_count) > 1 || \
(__mm) != current->active_mm) \
ptep_invalidate(__mm, __addr, __ptep); \
set_pte_at(__mm, __addr, __ptep, pte_wrprotect(__pte)); \
diff --git a/arch/s390/include/asm/tlb.h b/arch/s390/include/asm/tlb.h
index 81150b0..fd1c00d 100644
--- a/arch/s390/include/asm/tlb.h
+++ b/arch/s390/include/asm/tlb.h
@@ -50,8 +50,7 @@
struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
tlb->mm = mm;
- tlb->fullmm = full_mm_flush || (num_online_cpus() == 1) ||
- (atomic_read(&mm->mm_users) <= 1 && mm == current->active_mm);
+ tlb->fullmm = full_mm_flush;
tlb->nr_ptes = 0;
tlb->nr_pxds = TLB_NR_PTRS;
if (tlb->fullmm)
diff --git a/arch/s390/include/asm/tlbflush.h b/arch/s390/include/asm/tlbflush.h
index 304cffa..29d5d6d 100644
--- a/arch/s390/include/asm/tlbflush.h
+++ b/arch/s390/include/asm/tlbflush.h
@@ -94,8 +94,12 @@
static inline void __tlb_flush_mm_cond(struct mm_struct * mm)
{
- if (atomic_read(&mm->mm_users) <= 1 && mm == current->active_mm)
+ spin_lock(&mm->page_table_lock);
+ if (mm->context.flush_mm) {
__tlb_flush_mm(mm);
+ mm->context.flush_mm = 0;
+ }
+ spin_unlock(&mm->page_table_lock);
}
/*
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 541053e..8127ebd 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -583,6 +583,7 @@
sf->gprs[9] = (unsigned long) sf;
cpu_lowcore->save_area[15] = (unsigned long) sf;
__ctl_store(cpu_lowcore->cregs_save_area, 0, 15);
+ atomic_inc(&init_mm.context.attach_count);
asm volatile(
" stam 0,15,0(%0)"
: : "a" (&cpu_lowcore->access_regs_save_area) : "memory");
@@ -659,6 +660,7 @@
while (sigp_p(0, cpu, sigp_set_prefix) == sigp_busy)
udelay(10);
smp_free_lowcore(cpu);
+ atomic_dec(&init_mm.context.attach_count);
pr_info("Processor %d stopped\n", cpu);
}
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index acc91c7..30eb6d02 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -74,6 +74,8 @@
__ctl_load(S390_lowcore.kernel_asce, 13, 13);
__raw_local_irq_ssm(ssm_mask);
+ atomic_set(&init_mm.context.attach_count, 1);
+
sparse_memory_present_with_active_regions(MAX_NUMNODES);
sparse_init();
memset(max_zone_pfns, 0, sizeof(max_zone_pfns));