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authorLinus Torvalds <torvalds@linux-foundation.org>2011-05-29 11:32:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-29 11:32:28 -0700
commit6345d24daf0c1fffe6642081d783cdf653ebaa5c (patch)
tree415a253621279111bd481d48cbb86174c70b952a /include
parentcab0d85c8dfcad4d799f9c294571440c6f1db091 (diff)
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: [<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 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 <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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mm_types.h14
-rw-r--r--include/linux/sched.h1
2 files changed, 12 insertions, 3 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 2a78aae78c6..027935c86c6 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 bcddd013810..2a8621c4be1 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 *);