48 lines
1.4 KiB
Diff
48 lines
1.4 KiB
Diff
From 0b23a271be007ed8bed48ce446ed0ba53ef6022b Mon Sep 17 00:00:00 2001
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From: David Hildenbrand <dahi@linux.vnet.ibm.com>
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Date: Mon, 11 May 2015 17:52:13 +0200
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Subject: [PATCH 08/14] futex: UP futex_atomic_op_inuser() relies on disabled
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preemption
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.0/patches-4.0.4-rt1.tar.xz
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Let's explicitly disable/enable preemption in the !CONFIG_SMP version
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of futex_atomic_op_inuser, to prepare for pagefault_disable() not
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touching preemption anymore.
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Otherwise we might break mutual exclusion when relying on a get_user()/
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put_user() implementation.
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Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
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---
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include/asm-generic/futex.h | 5 +++--
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1 file changed, 3 insertions(+), 2 deletions(-)
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--- a/include/asm-generic/futex.h
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+++ b/include/asm-generic/futex.h
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@@ -8,8 +8,7 @@
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#ifndef CONFIG_SMP
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/*
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* The following implementation only for uniprocessor machines.
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- * For UP, it's relies on the fact that pagefault_disable() also disables
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- * preemption to ensure mutual exclusion.
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+ * It relies on preempt_disable() ensuring mutual exclusion.
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*
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*/
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@@ -38,6 +37,7 @@ futex_atomic_op_inuser(int encoded_op, u
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if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
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oparg = 1 << oparg;
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+ preempt_disable();
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pagefault_disable();
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ret = -EFAULT;
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@@ -72,6 +72,7 @@ futex_atomic_op_inuser(int encoded_op, u
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out_pagefault_enable:
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pagefault_enable();
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+ preempt_enable();
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if (ret == 0) {
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switch (cmp) {
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