From 7aec584eaf1cc1a527dcbe7d80f2e44e3bfcfe1d Mon Sep 17 00:00:00 2001 From: "Aneesh Kumar K.V" Date: Wed, 18 Sep 2019 19:31:03 +0530 Subject: [PATCH] powerpc/book3s64/radix: Remove WARN_ON in destroy_context() On failed task initialization due to memory allocation failures, we can call into destroy_context() with process_tb entry already populated. This patch forces the process_tb entry to zero in destroy_context(). With this patch, we lose the ability to track if we are destroying a context without flushing the process table entry. WARNING: CPU: 4 PID: 6368 at arch/powerpc/mm/mmu_context_book3s64.c:246 destroy_context+0x58/0x340 NIP [c0000000000875f8] destroy_context+0x58/0x340 LR [c00000000013da18] __mmdrop+0x78/0x270 Call Trace: [c000000f7db77c80] [c00000000013da18] __mmdrop+0x78/0x270 [c000000f7db77cf0] [c0000000004d6a34] __do_execve_file.isra.13+0xbd4/0x1000 [c000000f7db77e00] [c0000000004d7428] sys_execve+0x58/0x70 [c000000f7db77e30] [c00000000000b388] system_call+0x5c/0x70 Reported-by: Priya M.A Signed-off-by: Aneesh Kumar K.V [mpe: Reformat/tweak comment wording] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20190918140103.24395-1-aneesh.kumar@linux.ibm.com --- arch/powerpc/mm/book3s64/mmu_context.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/mm/book3s64/mmu_context.c b/arch/powerpc/mm/book3s64/mmu_context.c index 2d0cb5b..0ba30b8 100644 --- a/arch/powerpc/mm/book3s64/mmu_context.c +++ b/arch/powerpc/mm/book3s64/mmu_context.c @@ -256,8 +256,21 @@ void destroy_context(struct mm_struct *mm) #ifdef CONFIG_SPAPR_TCE_IOMMU WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list)); #endif + /* + * For tasks which were successfully initialized we end up calling + * arch_exit_mmap() which clears the process table entry. And + * arch_exit_mmap() is called before the required fullmm TLB flush + * which does a RIC=2 flush. Hence for an initialized task, we do clear + * any cached process table entries. + * + * The condition below handles the error case during task init. We have + * set the process table entry early and if we fail a task + * initialization, we need to ensure the process table entry is zeroed. + * We need not worry about process table entry caches because the task + * never ran with the PID value. + */ if (radix_enabled()) - WARN_ON(process_tb[mm->context.id].prtb0 != 0); + process_tb[mm->context.id].prtb0 = 0; else subpage_prot_free(mm); destroy_contexts(&mm->context); -- 2.7.4