43 lines
1.1 KiB
C
43 lines
1.1 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Preemptible hypercalls
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*
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* Copyright (C) 2014 Citrix Systems R&D ltd.
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*/
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#include <linux/sched.h>
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#include <xen/xen-ops.h>
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#ifndef CONFIG_PREEMPT
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/*
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* Some hypercalls issued by the toolstack can take many 10s of
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* seconds. Allow tasks running hypercalls via the privcmd driver to
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* be voluntarily preempted even if full kernel preemption is
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* disabled.
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*
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* Such preemptible hypercalls are bracketed by
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* xen_preemptible_hcall_begin() and xen_preemptible_hcall_end()
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* calls.
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*/
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DEFINE_PER_CPU(bool, xen_in_preemptible_hcall);
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EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall);
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asmlinkage __visible void xen_maybe_preempt_hcall(void)
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{
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if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
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&& need_resched() && !preempt_count())) {
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/*
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* Clear flag as we may be rescheduled on a different
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* cpu.
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*/
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__this_cpu_write(xen_in_preemptible_hcall, false);
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local_irq_enable();
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cond_resched();
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local_irq_disable();
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__this_cpu_write(xen_in_preemptible_hcall, true);
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}
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}
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#endif /* CONFIG_PREEMPT */
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