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authorChris Metcalf <cmetcalf@tilera.com>2012-03-29 15:50:08 -0400
committerChris Metcalf <cmetcalf@tilera.com>2012-04-02 12:13:22 -0400
commit719ea79e330c5e1a17fb7e4cf352a81e4c84cff5 (patch)
tree08fc6a29a0430599b9e91e9e87945b0b6eb2ef6a /arch/tile/mm
parent5f220704127ae70db519fabbda4ece649eadac7f (diff)
arch/tile: fix up locking in pgtable.c slightly
We should be holding the init_mm.page_table_lock in shatter_huge_page() since we are modifying the kernel page tables. Then, only if we are walking the other root page tables to update them, do we want to take the pgd_lock. Add a comment about taking the pgd_lock that we always do it with interrupts disabled and therefore are not at risk from the tlbflush IPI deadlock as is seen on x86. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Diffstat (limited to 'arch/tile/mm')
-rw-r--r--arch/tile/mm/pgtable.c22
1 files changed, 12 insertions, 10 deletions
diff --git a/arch/tile/mm/pgtable.c b/arch/tile/mm/pgtable.c
index 6b9a109c3e3..2410aa899b3 100644
--- a/arch/tile/mm/pgtable.c
+++ b/arch/tile/mm/pgtable.c
@@ -177,14 +177,10 @@ void shatter_huge_page(unsigned long addr)
if (!pmd_huge_page(*pmd))
return;
- /*
- * Grab the pgd_lock, since we may need it to walk the pgd_list,
- * and since we need some kind of lock here to avoid races.
- */
- spin_lock_irqsave(&pgd_lock, flags);
+ spin_lock_irqsave(&init_mm.page_table_lock, flags);
if (!pmd_huge_page(*pmd)) {
/* Lost the race to convert the huge page. */
- spin_unlock_irqrestore(&pgd_lock, flags);
+ spin_unlock_irqrestore(&init_mm.page_table_lock, flags);
return;
}
@@ -194,6 +190,7 @@ void shatter_huge_page(unsigned long addr)
#ifdef __PAGETABLE_PMD_FOLDED
/* Walk every pgd on the system and update the pmd there. */
+ spin_lock(&pgd_lock);
list_for_each(pos, &pgd_list) {
pmd_t *copy_pmd;
pgd = list_to_pgd(pos) + pgd_index(addr);
@@ -201,6 +198,7 @@ void shatter_huge_page(unsigned long addr)
copy_pmd = pmd_offset(pud, addr);
__set_pmd(copy_pmd, *pmd);
}
+ spin_unlock(&pgd_lock);
#endif
/* Tell every cpu to notice the change. */
@@ -208,7 +206,7 @@ void shatter_huge_page(unsigned long addr)
cpu_possible_mask, NULL, 0);
/* Hold the lock until the TLB flush is finished to avoid races. */
- spin_unlock_irqrestore(&pgd_lock, flags);
+ spin_unlock_irqrestore(&init_mm.page_table_lock, flags);
}
/*
@@ -217,9 +215,13 @@ void shatter_huge_page(unsigned long addr)
* against pageattr.c; it is the unique case in which a valid change
* of kernel pagetables can't be lazily synchronized by vmalloc faults.
* vmalloc faults work because attached pagetables are never freed.
- * The locking scheme was chosen on the basis of manfred's
- * recommendations and having no core impact whatsoever.
- * -- wli
+ *
+ * The lock is always taken with interrupts disabled, unlike on x86
+ * and other platforms, because we need to take the lock in
+ * shatter_huge_page(), which may be called from an interrupt context.
+ * We are not at risk from the tlbflush IPI deadlock that was seen on
+ * x86, since we use the flush_remote() API to have the hypervisor do
+ * the TLB flushes regardless of irq disabling.
*/
DEFINE_SPINLOCK(pgd_lock);
LIST_HEAD(pgd_list);