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Subject[PATCH] powerpc: fix __get_user_pages_fast() irq handling
From 1454d5ca6209926a52c2fdea9ba41a41a33e4046 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Tue, 8 Oct 2013 09:46:00 +0200
Subject: [PATCH] powerpc: fix __get_user_pages_fast() irq handling

__get_user_pages_fast() may be called with interrupts disabled (see e.g.
get_futex_key() in kernel/futex.c) and therefore should use local_irq_save()
and local_irq_restore() instead of local_irq_disable()/enable().

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
---

Please note that this patch is completely untested; not even compile
tested. I just realized that there seems to be a bug when looking at
the powerpc code ;)

arch/powerpc/mm/gup.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/gup.c b/arch/powerpc/mm/gup.c
index 6936547..c5f734e 100644
--- a/arch/powerpc/mm/gup.c
+++ b/arch/powerpc/mm/gup.c
@@ -123,6 +123,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct mm_struct *mm = current->mm;
unsigned long addr, len, end;
unsigned long next;
+ unsigned long flags;
pgd_t *pgdp;
int nr = 0;

@@ -156,7 +157,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
* So long as we atomically load page table pointers versus teardown,
* we can follow the address down to the the page and take a ref on it.
*/
- local_irq_disable();
+ local_irq_save(flags);

pgdp = pgd_offset(mm, addr);
do {
@@ -179,7 +180,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
break;
} while (pgdp++, addr = next, addr != end);

- local_irq_enable();
+ local_irq_restore(flags);

return nr;
}
--
1.8.3.4


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