linux/drivers/xen/preempt.c
Konstantin Khlebnikov a7da51ae10 xen/preempt: use need_resched() instead of should_resched()
This code is used only when CONFIG_PREEMPT=n and only in non-atomic
context: xen_in_preemptible_hcall is set only in
privcmd_ioctl_hypercall().  Thus preempt_count is zero and
should_resched() is equal to need_resched().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2015-08-20 12:24:14 +01:00

45 lines
1.2 KiB
C

/*
* Preemptible hypercalls
*
* Copyright (C) 2014 Citrix Systems R&D ltd.
*
* This source code is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*/
#include <linux/sched.h>
#include <xen/xen-ops.h>
#ifndef CONFIG_PREEMPT
/*
* 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);
_cond_resched();
__this_cpu_write(xen_in_preemptible_hcall, true);
}
}
#endif /* CONFIG_PREEMPT */