linux/drivers/xen/preempt.c
Linus Torvalds 54dedb5b57 xen: branch for v5.6-rc3
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Merge tag 'for-linus-5.6-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen fixes from Juergen Gross:
 "Two small fixes for Xen:

   - a fix to avoid warnings with new gcc

   - a fix for incorrectly disabled interrupts when calling
     _cond_resched()"

* tag 'for-linus-5.6-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: Enable interrupts when calling _cond_resched()
  x86/xen: Distribute switch variables for initialization
2020-02-21 16:10:10 -08:00

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1.0 KiB
C

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