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/kernel/smp.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/s390/kernel') 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); } -- cgit v1.2.3