linux-kernel - [PATCH 4.2.y-ckt 191/218] sched/preempt, sh: kmap

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Message-Id: <1459455431-12687-192-git-send-email-kamal@canonical.com>
Date:	Thu, 31 Mar 2016 13:16:44 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	Rich Felker <dalias@...c.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 191/218] sched/preempt, sh: kmap_coherent relies on disabled preemption

4.2.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: David Hildenbrand <dahi@...ux.vnet.ibm.com>

commit b15d53d009558d14c4f394a6d1fa2039c7f45c43 upstream.

kmap_coherent needs disabled preemption to not schedule in the critical
section, just like kmap_coherent on mips and kmap_atomic in general.

Fixes: 8222dbe21e79 "sched/preempt, mm/fault: Decouple preemption from the page fault logic"
Reported-by: Hans Verkuil <hverkuil@...all.nl>
Signed-off-by: David Hildenbrand <dahi@...ux.vnet.ibm.com>
Tested-by: Hans Verkuil <hans.verkuil@...co.com>
Signed-off-by: Rich Felker <dalias@...c.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/sh/mm/kmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/sh/mm/kmap.c b/arch/sh/mm/kmap.c
index ec29e14..bf25d7c 100644
--- a/arch/sh/mm/kmap.c
+++ b/arch/sh/mm/kmap.c
@@ -36,6 +36,7 @@ void *kmap_coherent(struct page *page, unsigned long addr)
 
 	BUG_ON(!test_bit(PG_dcache_clean, &page->flags));
 
+	preempt_disable();
 	pagefault_disable();
 
 	idx = FIX_CMAP_END -
@@ -64,4 +65,5 @@ void kunmap_coherent(void *kvaddr)
 	}
 
 	pagefault_enable();
+	preempt_enable();
 }
-- 
2.7.4