| /* |
| * 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 */ |