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mm: Fix boot crash in mm_alloc()

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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: [<c11ae035>] find_next_bit+0x55/0xb0
    Call Trace:
     [<c11addda>] cpumask_any_but+0x2a/0x70
     [<c102396b>] flush_tlb_mm+0x2b/0x80
     [<c1022705>] pud_populate+0x35/0x50
     [<c10227ba>] pgd_alloc+0x9a/0xf0
     [<c103a3fc>] mm_init+0xec/0x120
     [<c103a7a3>] mm_alloc+0x53/0xd0

which was introduced by commit de03c72cfc ("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 <tglx@linutronix.de>
Reported-by: Ingo Molnar <mingo@elte.hu>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds
2011-05-29 11:32:28 -07:00
parent cab0d85c8d
commit 6345d24daf
4 changed files with 23 additions and 36 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/mm_types.h
View File

@@ -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)
{

1
include/linux/sched.h
View File

@@ -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 *);