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Commit 8bdafa39 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt
Browse files

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: default avatarAnton Blanchard <anton@samba.org>
Cc: <stable@kernel.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent a1194097

arch/powerpc/mm/mmu_context_hash64.c

+6 −6
Original line number Diff line number Diff line
@@ -136,8 +136,8 @@ int use_cop(unsigned long acop, struct mm_struct *mm) 
	if (!mm || !acop)

		return -EINVAL;



	/* We need to make sure mm_users doesn't change */

	down_read(&mm->mmap_sem);

	/* The page_table_lock ensures mm_users won't change under us */

	spin_lock(&mm->page_table_lock);

	spin_lock(mm->context.cop_lockp);



	if (mm->context.cop_pid == COP_PID_NONE) {
@@ -164,7 +164,7 @@ int use_cop(unsigned long acop, struct mm_struct *mm) 


out:

	spin_unlock(mm->context.cop_lockp);

	up_read(&mm->mmap_sem);

	spin_unlock(&mm->page_table_lock);



	return ret;

}
@@ -185,8 +185,8 @@ void drop_cop(unsigned long acop, struct mm_struct *mm) 
	if (WARN_ON_ONCE(!mm))

		return;



	/* We need to make sure mm_users doesn't change */

	down_read(&mm->mmap_sem);

	/* The page_table_lock ensures mm_users won't change under us */

	spin_lock(&mm->page_table_lock);

	spin_lock(mm->context.cop_lockp);



	mm->context.acop &= ~acop;
@@ -213,7 +213,7 @@ void drop_cop(unsigned long acop, struct mm_struct *mm) 
	}



	spin_unlock(mm->context.cop_lockp);

	up_read(&mm->mmap_sem);

	spin_unlock(&mm->page_table_lock);

}

EXPORT_SYMBOL_GPL(drop_cop);