powerpc: Fix deadlock in icswx code
The icswx code introduced an A-B B-A deadlock: CPU0 CPU1 ---- ---- lock(&anon_vma->mutex); lock(&mm->mmap_sem); lock(&anon_vma->mutex); lock(&mm->mmap_sem); Instead of using the mmap_sem to keep mm_users constant, take the page table spinlock. Signed-off-by: Anton Blanchard <anton@samba.org> Cc: <stable@kernel.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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@ -136,8 +136,8 @@ int use_cop(unsigned long acop, struct mm_struct *mm)
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if (!mm || !acop)
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if (!mm || !acop)
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return -EINVAL;
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return -EINVAL;
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/* We need to make sure mm_users doesn't change */
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/* The page_table_lock ensures mm_users won't change under us */
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down_read(&mm->mmap_sem);
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spin_lock(&mm->page_table_lock);
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spin_lock(mm->context.cop_lockp);
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spin_lock(mm->context.cop_lockp);
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if (mm->context.cop_pid == COP_PID_NONE) {
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if (mm->context.cop_pid == COP_PID_NONE) {
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@ -164,7 +164,7 @@ int use_cop(unsigned long acop, struct mm_struct *mm)
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out:
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out:
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spin_unlock(mm->context.cop_lockp);
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spin_unlock(mm->context.cop_lockp);
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up_read(&mm->mmap_sem);
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spin_unlock(&mm->page_table_lock);
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return ret;
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return ret;
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}
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}
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@ -185,8 +185,8 @@ void drop_cop(unsigned long acop, struct mm_struct *mm)
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if (WARN_ON_ONCE(!mm))
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if (WARN_ON_ONCE(!mm))
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return;
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return;
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/* We need to make sure mm_users doesn't change */
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/* The page_table_lock ensures mm_users won't change under us */
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down_read(&mm->mmap_sem);
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spin_lock(&mm->page_table_lock);
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spin_lock(mm->context.cop_lockp);
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spin_lock(mm->context.cop_lockp);
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mm->context.acop &= ~acop;
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mm->context.acop &= ~acop;
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@ -213,7 +213,7 @@ void drop_cop(unsigned long acop, struct mm_struct *mm)
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}
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}
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spin_unlock(mm->context.cop_lockp);
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spin_unlock(mm->context.cop_lockp);
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up_read(&mm->mmap_sem);
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spin_unlock(&mm->page_table_lock);
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}
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}
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EXPORT_SYMBOL_GPL(drop_cop);
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EXPORT_SYMBOL_GPL(drop_cop);
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