Re: [PATCH] powerpc: Fix deadlock in icswx code
From: Jimi Xenidis <hidden>
Date: 2011-09-15 13:09:52
On Sep 14, 2011, at 2:43 PM, Anton Blanchard wrote: Hi Anton, It would really help me a lot if you could review and maybe merge this = with my earlier patch that splits this file. <http://patchwork.ozlabs.org/patch/109103/> All it does is split.. I promise. You don't have to take the other stuff.. yet :) -JX
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=20 The icswx code introduced an A-B B-A deadlock: =20 CPU0 CPU1 ---- ---- lock(&anon_vma->mutex); lock(&mm->mmap_sem); lock(&anon_vma->mutex); lock(&mm->mmap_sem); =20 Instead of using the mmap_sem to keep mm_users constant, take the page table spinlock. =20 Signed-off-by: Anton Blanchard <redacted> Cc: <stable@kernel.org> --- =20diff --git a/arch/powerpc/mm/mmu_context_hash64.c =
b/arch/powerpc/mm/mmu_context_hash64.c
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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)
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if (!mm || !acop) return -EINVAL; =20 - /* 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); =20 if (mm->context.cop_pid =3D=3D COP_PID_NONE) {@@ -164,7 +164,7 @@ int use_cop(unsigned long acop, struct mm_struct =
*mm)
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=20 out: spin_unlock(mm->context.cop_lockp); - up_read(&mm->mmap_sem); + spin_unlock(&mm->page_table_lock); =20 return ret; }@@ -185,8 +185,8 @@ void drop_cop(unsigned long acop, struct mm_struct =
*mm)
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if (WARN_ON_ONCE(!mm)) return; =20 - /* 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); =20 mm->context.acop &=3D ~acop;@@ -213,7 +213,7 @@ void drop_cop(unsigned long acop, struct mm_struct =
*mm)
} =20 spin_unlock(mm->context.cop_lockp); - up_read(&mm->mmap_sem); + spin_unlock(&mm->page_table_lock); } EXPORT_SYMBOL_GPL(drop_cop); =20 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev