From patchwork Wed Sep 14 19:43:15 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: powerpc: Fix deadlock in icswx code Date: Wed, 14 Sep 2011 09:43:15 -0000 From: Anton Blanchard X-Patchwork-Id: 114701 Message-Id: <20110915054315.5e5ae062@kryten> To: benh@kernel.crashing.org, paulus@samba.org Cc: linuxppc-dev@lists.ozlabs.org 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 Cc: --- diff --git a/arch/powerpc/mm/mmu_context_hash64.c b/arch/powerpc/mm/mmu_context_hash64.c index 3bafc3d..4ff587e 100644 --- a/arch/powerpc/mm/mmu_context_hash64.c +++ b/arch/powerpc/mm/mmu_context_hash64.c @@ -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);