| From | David Hildenbrand <> | Subject | [PATCH v1 11/15] arm/futex: UP futex_atomic_op_inuser() relies on disabled preemption | Date | Mon, 11 May 2015 17:52:16 +0200 |
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The !CONFIG_SMP implementation of futex_atomic_op_inuser() seems to rely on disabled preemption to guarantee mutual exclusion.
From commit e589ed23dd27: "For UP it's enough to disable preemption to ensure mutual exclusion..." From the code itself: "!SMP, we can work around lack of atomic ops by disabling preemption"
Let's make this explicit, to prepare for pagefault_disable() not touching preemption anymore.
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com> --- arch/arm/include/asm/futex.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h index 255bfd1..5eed828 100644 --- a/arch/arm/include/asm/futex.h +++ b/arch/arm/include/asm/futex.h @@ -127,7 +127,10 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr) if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))) return -EFAULT; - pagefault_disable(); /* implies preempt_disable() */ +#ifndef CONFIG_SMP + preempt_disable(); +#endif + pagefault_disable(); switch (op) { case FUTEX_OP_SET: @@ -149,7 +152,10 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr) ret = -ENOSYS; } - pagefault_enable(); /* subsumes preempt_enable() */ + pagefault_enable(); +#ifndef CONFIG_SMP + preempt_enable(); +#endif if (!ret) { switch (cmp) { -- 2.1.4
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