From 6345d24daf0c1fffe6642081d783cdf653ebaa5c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 29 May 2011 11:32:28 -0700 Subject: mm: Fix boot crash in mm_alloc() Thomas Gleixner reports that we now have a boot crash triggered by CONFIG_CPUMASK_OFFSTACK=y: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] find_next_bit+0x55/0xb0 Call Trace: [] cpumask_any_but+0x2a/0x70 [] flush_tlb_mm+0x2b/0x80 [] pud_populate+0x35/0x50 [] pgd_alloc+0x9a/0xf0 [] mm_init+0xec/0x120 [] mm_alloc+0x53/0xd0 which was introduced by commit de03c72cfce5 ("mm: convert mm->cpu_vm_cpumask into cpumask_var_t"), and is due to wrong ordering of mm_init() vs mm_init_cpumask Thomas wrote a patch to just fix the ordering of initialization, but I hate the new double allocation in the fork path, so I ended up instead doing some more radical surgery to clean it all up. Reported-by: Thomas Gleixner Reported-by: Ingo Molnar Cc: KOSAKI Motohiro Cc: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm_types.h | 14 ++++++++++++-- include/linux/sched.h | 1 - 2 files changed, 12 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 2a78aae78c69..027935c86c68 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -264,6 +264,8 @@ struct mm_struct { struct linux_binfmt *binfmt; + cpumask_var_t cpu_vm_mask_var; + /* Architecture-specific MM context */ mm_context_t context; @@ -311,10 +313,18 @@ struct mm_struct { #ifdef CONFIG_TRANSPARENT_HUGEPAGE pgtable_t pmd_huge_pte; /* protected by page_table_lock */ #endif - - cpumask_var_t cpu_vm_mask_var; +#ifdef CONFIG_CPUMASK_OFFSTACK + struct cpumask cpumask_allocation; +#endif }; +static inline void mm_init_cpumask(struct mm_struct *mm) +{ +#ifdef CONFIG_CPUMASK_OFFSTACK + mm->cpu_vm_mask_var = &mm->cpumask_allocation; +#endif +} + /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */ static inline cpumask_t *mm_cpumask(struct mm_struct *mm) { diff --git a/include/linux/sched.h b/include/linux/sched.h index bcddd0138105..2a8621c4be1e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2194,7 +2194,6 @@ static inline void mmdrop(struct mm_struct * mm) if (unlikely(atomic_dec_and_test(&mm->mm_count))) __mmdrop(mm); } -extern int mm_init_cpumask(struct mm_struct *mm, struct mm_struct *oldmm); /* mmput gets rid of the mappings and all user-space */ extern void mmput(struct mm_struct *); -- cgit v1.2.3