[PATCH RFC 08/15] futex: UP futex_atomic_op_inuser() relies on disabled preemption
From: David Hildenbrand <hidden>
Date: 2015-05-06 17:53:14
Also in:
linux-mm, lkml
Subsystem:
futex subsystem, generic include/asm header files, the rest · Maintainers:
Thomas Gleixner, Ingo Molnar, Arnd Bergmann, Linus Torvalds
Let's explicitly disable/enable preemption in the !CONFIG_SMP version of futex_atomic_op_inuser, to prepare for pagefault_disable() not touching preemption anymore. Otherwise we might break mutual exclusion when relying on a get_user()/ put_user() implementation. Signed-off-by: David Hildenbrand <redacted> --- include/asm-generic/futex.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
index b59b5a5..3586017 100644
--- a/include/asm-generic/futex.h
+++ b/include/asm-generic/futex.h@@ -8,8 +8,7 @@ #ifndef CONFIG_SMP /* * The following implementation only for uniprocessor machines. - * For UP, it's relies on the fact that pagefault_disable() also disables - * preemption to ensure mutual exclusion. + * It relies on preempt_disable() ensuring mutual exclusion. * */
@@ -38,6 +37,7 @@ futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr) if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) oparg = 1 << oparg; + preempt_disable(); pagefault_disable(); ret = -EFAULT;
@@ -72,6 +72,7 @@ futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr) out_pagefault_enable: pagefault_enable(); + preempt_enable(); if (ret == 0) { switch (cmp) {
--
2.1.4
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