From 050eef364ad700590a605a0749f825cab4834b1e Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Tue, 24 Aug 2010 09:26:21 +0200 Subject: [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 --- arch/s390/include/asm/hugetlb.h | 4 +++- arch/s390/include/asm/mmu.h | 2 ++ arch/s390/include/asm/mmu_context.h | 9 +++++++++ arch/s390/include/asm/pgtable.h | 6 ++++-- arch/s390/include/asm/tlb.h | 3 +-- arch/s390/include/asm/tlbflush.h | 6 +++++- arch/s390/kernel/smp.c | 2 ++ arch/s390/mm/init.c | 2 ++ 8 files changed, 28 insertions(+), 6 deletions(-) (limited to 'arch') diff --git a/arch/s390/include/asm/hugetlb.h b/arch/s390/include/asm/hugetlb.h index 670a1d1745d2..bb8343d157bc 100644 --- a/arch/s390/include/asm/hugetlb.h +++ b/arch/s390/include/asm/hugetlb.h @@ -97,6 +97,7 @@ static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm, { pte_t pte = huge_ptep_get(ptep); + mm->context.flush_mm = 1; pmd_clear((pmd_t *) ptep); return pte; } @@ -167,7 +168,8 @@ static inline void huge_ptep_invalidate(struct mm_struct *mm, ({ \ 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 99e3409102b9..78522cdefdd4 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 976e273988c2..a6f0e7cc9cde 100644 --- a/arch/s390/include/asm/mmu_context.h +++ b/arch/s390/include/asm/mmu_context.h @@ -11,11 +11,14 @@ #include #include +#include #include 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 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, { 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 89a504c3f12e..3157441ee1da 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -880,7 +880,8 @@ static inline void ptep_invalidate(struct mm_struct *mm, #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 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm, ({ \ 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 81150b053689..fd1c00d08bf5 100644 --- a/arch/s390/include/asm/tlb.h +++ b/arch/s390/include/asm/tlb.h @@ -50,8 +50,7 @@ static inline struct mmu_gather *tlb_gather_mmu(struct mm_struct *mm, 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 304cffa623e1..29d5d6d4becc 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(struct mm_struct * mm) 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 541053ed234e..8127ebd59c4d 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -583,6 +583,7 @@ int __cpuinit __cpu_up(unsigned int cpu) 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 @@ void __cpu_die(unsigned int cpu) 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 acc91c75bc94..30eb6d02ddb8 100644 --- a/arch/s390/mm/init.c +++ b/arch/s390/mm/init.c @@ -74,6 +74,8 @@ void __init paging_init(void) __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)); -- cgit v1.2.3