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/mmu_context.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/s390/include/asm/mmu_context.h') diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h index 976e273988c..a6f0e7cc9cd 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) -- cgit v1.2.3