[kernel/f16] Add patch to fix deadlock in ppc64 icswx code (rhbz 737984)

[Josh Boyer]

commit 9d940d046e9b493a71c894fb77135feb2ae07ef9
Author: Josh Boyer <jwboyer at redhat.com>
Date:   Wed Sep 14 16:12:02 2011 -0400

    Add patch to fix deadlock in ppc64 icswx code (rhbz 737984)

 kernel.spec                              |    7 +++
 powerpc-Fix-deadlock-in-icswx-code.patch |   74 ++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 0 deletions(-)
---
diff --git a/kernel.spec b/kernel.spec
index c825aa9..526c562 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -735,6 +735,8 @@ Patch13010: ibmveth-Fix-DMA-unmap-error.patch
 Patch13011: ibmveth-Fix-issue-with-DMA-mapping-failure.patch
 Patch13012: ibmveth-Checksum-offload-is-always-disabled.patch
 
+Patch13013: powerpc-Fix-deadlock-in-icswx-code.patch
+
 Patch20000: utrace.patch
 
 # Flattened devicetree support
@@ -1359,6 +1361,8 @@ ApplyPatch ibmveth-Fix-DMA-unmap-error.patch
 ApplyPatch ibmveth-Fix-issue-with-DMA-mapping-failure.patch
 ApplyPatch ibmveth-Checksum-offload-is-always-disabled.patch
 
+ApplyPatch powerpc-Fix-deadlock-in-icswx-code.patch
+
 # utrace.
 ApplyPatch utrace.patch
 
@@ -2061,6 +2065,9 @@ fi
 # and build.
 
 %changelog
+* Wed Sep 14 2011 Josh Boyer <jwboyer at redhat.com>
+- Add patch to fix deadlock in ppc64 icswx (rhbz 737984)
+
 * Wed Sep 14 2011 Neil Horman <nhorman at redhat.com>
 - Enable CONFIG_IP_VS_IPV6 (bz 738194)
 
diff --git a/powerpc-Fix-deadlock-in-icswx-code.patch b/powerpc-Fix-deadlock-in-icswx-code.patch
new file mode 100644
index 0000000..a2ce3cf
--- /dev/null
+++ b/powerpc-Fix-deadlock-in-icswx-code.patch
@@ -0,0 +1,74 @@
+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 <anton at samba.org>
+X-Patchwork-Id: 114701
+Message-Id: <20110915054315.5e5ae062 at kryten>
+To: benh at kernel.crashing.org, paulus at samba.org
+Cc: linuxppc-dev at 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 <anton at samba.org>
+Cc: <stable at kernel.org>
+
+---
+
+
+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);
+