50 lines
1.5 KiB
Diff
50 lines
1.5 KiB
Diff
From 4a09aa40684aa2fd01fd52087553d19e99a59d91 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 17:52:16 +0200
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Subject: [PATCH 11/14] arm/futex: UP futex_atomic_op_inuser() relies on
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disabled preemption
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.0/patches-4.0.5-rt3.tar.xz
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The !CONFIG_SMP implementation of futex_atomic_op_inuser() seems to rely
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on disabled preemption to guarantee mutual exclusion.
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From commit e589ed23dd27:
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"For UP it's enough to disable preemption to ensure mutual exclusion..."
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From the code itself:
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"!SMP, we can work around lack of atomic ops by disabling preemption"
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Let's make this explicit, to prepare for pagefault_disable() not
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touching preemption anymore.
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Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
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---
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arch/arm/include/asm/futex.h | 10 ++++++++--
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1 file changed, 8 insertions(+), 2 deletions(-)
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--- a/arch/arm/include/asm/futex.h
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+++ b/arch/arm/include/asm/futex.h
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@@ -127,7 +127,10 @@ futex_atomic_op_inuser (int encoded_op,
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if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
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return -EFAULT;
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- pagefault_disable(); /* implies preempt_disable() */
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+#ifndef CONFIG_SMP
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+ preempt_disable();
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+#endif
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+ pagefault_disable();
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switch (op) {
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case FUTEX_OP_SET:
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@@ -149,7 +152,10 @@ futex_atomic_op_inuser (int encoded_op,
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ret = -ENOSYS;
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}
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- pagefault_enable(); /* subsumes preempt_enable() */
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+ pagefault_enable();
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+#ifndef CONFIG_SMP
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+ preempt_enable();
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+#endif
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if (!ret) {
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switch (cmp) {
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