Messages in this thread Patch in this message | | | Date | Sun, 7 Jan 2007 11:44:21 +0100 | From | Martin Schwidefsky <> | Subject | [S390] don't call handle_mm_fault() if in an atomic context. |
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From: Heiko Carstens <heiko.carstens@de.ibm.com>
[S390] don't call handle_mm_fault() if in an atomic context.
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> ---
arch/s390/lib/uaccess_pt.c | 3 +++ arch/s390/lib/uaccess_std.c | 3 --- include/asm-s390/futex.h | 2 ++ 3 files changed, 5 insertions(+), 3 deletions(-)
diff -urpN linux-2.6/arch/s390/lib/uaccess_pt.c linux-2.6-patched/arch/s390/lib/uaccess_pt.c --- linux-2.6/arch/s390/lib/uaccess_pt.c 2007-01-06 15:20:00.000000000 +0100 +++ linux-2.6-patched/arch/s390/lib/uaccess_pt.c 2007-01-06 15:20:34.000000000 +0100 @@ -8,6 +8,7 @@ */ #include <linux/errno.h> +#include <linux/hardirq.h> #include <linux/mm.h> #include <asm/uaccess.h> #include <asm/futex.h> @@ -18,6 +19,8 @@ static inline int __handle_fault(struct 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)) diff -urpN linux-2.6/arch/s390/lib/uaccess_std.c linux-2.6-patched/arch/s390/lib/uaccess_std.c --- linux-2.6/arch/s390/lib/uaccess_std.c 2007-01-06 15:20:00.000000000 +0100 +++ linux-2.6-patched/arch/s390/lib/uaccess_std.c 2007-01-06 15:20:34.000000000 +0100 @@ -258,8 +258,6 @@ int futex_atomic_op(int op, int __user * { int oldval = 0, newval, ret; - pagefault_disable(); - switch (op) { case FUTEX_OP_SET: __futex_atomic_op("lr %2,%5\n", @@ -284,7 +282,6 @@ int futex_atomic_op(int op, int __user * default: ret = -ENOSYS; } - pagefault_enable(); *old = oldval; return ret; } diff -urpN linux-2.6/include/asm-s390/futex.h linux-2.6-patched/include/asm-s390/futex.h --- linux-2.6/include/asm-s390/futex.h 2006-11-29 22:57:37.000000000 +0100 +++ linux-2.6-patched/include/asm-s390/futex.h 2007-01-06 15:20:34.000000000 +0100 @@ -21,7 +21,9 @@ static inline int futex_atomic_op_inuser 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) { - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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