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[S390] don't call handle_mm_fault() if in an atomic context.
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There are several places in the futex code where a spin_lock is held
and still uaccesses happen. Deadlocks are avoided by increasing the
preempt count. The pagefault handler will then not take any locks
but will immediately search the fixup tables.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Heiko Carstens authored and Martin Schwidefsky committed Jan 9, 2007
1 parent de338a3 commit d8ad075
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Showing 3 changed files with 6 additions and 4 deletions.
3 changes: 3 additions & 0 deletions arch/s390/lib/uaccess_pt.c
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
*/

#include <linux/errno.h>
#include <linux/hardirq.h>
#include <linux/mm.h>
#include <asm/uaccess.h>
#include <asm/futex.h>
Expand All @@ -18,6 +19,8 @@ static inline int __handle_fault(struct mm_struct *mm, unsigned long address,
struct vm_area_struct *vma;
int ret = -EFAULT;

if (in_atomic())
return ret;
down_read(&mm->mmap_sem);
vma = find_vma(mm, address);
if (unlikely(!vma))
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3 changes: 0 additions & 3 deletions arch/s390/lib/uaccess_std.c
Original file line number Diff line number Diff line change
Expand Up @@ -258,8 +258,6 @@ int futex_atomic_op(int op, int __user *uaddr, int oparg, int *old)
{
int oldval = 0, newval, ret;

pagefault_disable();

switch (op) {
case FUTEX_OP_SET:
__futex_atomic_op("lr %2,%5\n",
Expand All @@ -284,7 +282,6 @@ int futex_atomic_op(int op, int __user *uaddr, int oparg, int *old)
default:
ret = -ENOSYS;
}
pagefault_enable();
*old = oldval;
return ret;
}
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4 changes: 3 additions & 1 deletion include/asm-s390/futex.h
Original file line number Diff line number Diff line change
Expand Up @@ -4,8 +4,8 @@
#ifdef __KERNEL__

#include <linux/futex.h>
#include <linux/uaccess.h>
#include <asm/errno.h>
#include <asm/uaccess.h>

static inline int futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
{
Expand All @@ -21,7 +21,9 @@ static inline int futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
if (! access_ok (VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;

pagefault_disable();
ret = uaccess.futex_atomic_op(op, uaddr, oparg, &oldval);
pagefault_enable();

if (!ret) {
switch (cmp) {
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